About the National Science and Technology Council

The National Science and Technology Council (NSTC) was established by Executive Order on November 

23, 1993. This cabinet-level council is the principle means by which the President coordinates science, 

space, and technology policies across the Federal Government. NSTC acts as a virtual agency for science 

and technology to coordinate diverse paths of the Federal research and development enterprise. 

An important objective of the NSTC is the establishment of clear national goals for Federal science 

and technology investments in areas ranging from information technologies and health research to 

improving transportation systems and strengthening fundamental research. The Council prepares research 

and development strategies that are coordinated across the Federal agencies to form a comprehensive 

investment package aimed at accomplishing multiple national goals. 

Please call the NSTC Executive Secretariat at 202-456-6101 to obtain additional information regarding the 

NSTC, or see http://www.ostp.gov/nstc/html/NSTC_Home.html.

About the Office of Science and Technology Policy

The Office of Science and Technology Policy (OSTP) was established by the National Science and 

Technology Policy, Organization and Priorities Act of 1976. OSTP’s responsibilities include advising 

the President in policy formulation and budget development on all questions in which S&T are important 

elements; articulating the President’s S&T policies and programs; and fostering strong partnerships among 

Federal, state and local governments, and the scientific communities in industry and academe.

For additional copies and further information, contact the Office of Science and Technology Policy at (202) 

395-7347 (voice), (202) 456-6027 (fax) or see our web site at www.ostp.gov. 

About this Report 

In this report the Interagency Working Group on the Physics of the Universe responds to the National 

Research Council’s (NRC) 2002 report, Connecting Quarks with the Cosmos: Eleven Science Questions 

for the New Century. The Physics of the Universe group examines the status of the Federal government’s 

current investments aimed at answering the eleven questions in the NRC report. Based upon that 

assessment, the group prioritized the new facilities needed to advance understanding in each of these areas. 

Consistent with a goal of the President’s Management Agenda to manage Federal R&D investments as a 

portfolio of interconnected activities, this report lays out a plan for exciting discovery at the intersection of 

physics and astronomy.
A 21st Century Frontier of Discovery: 

The Physics of the Universe

A Strategic Plan for Federal Research 

at the Intersection of Physics and Astronomy

A Report of the Interagency Working Group 

on the Physics of the Universe

National Science and Technology Council 

Committee on Science

February 2004

i

Contents

Summary 4

Summary of Recommendations 5

A Federal Research Program on the Physics of the Universe 6

R&D Investment Criteria 7

Programmatic Priorities 9

Prioritized Findings and Recommendations 12

The Opportunity: Eleven Science Questions for the New Century 18

Question 1. What is Dark Matter? 20

Question 2. What is the Nature of Dark Energy? 23

Question 3. How Did the Universe Begin? 25

Question 4. Did Einstein Have the Last Word on Gravity? 29

Question 5. What Are the Masses of the Neutrinos 

 and How Have They Shaped the Evolution of the Universe? 31

Question 6. How Do Cosmic Accelerators Work and What Are They Accelerating? 34

Question 7. Are Protons Unstable? 39

Question 8. What Are the New States of Matter 

 at Exceedingly High Density and Temperature? 41

Question 9. Are There Additional Space-Time Dimensions? 43

Question 10. How Were the Elements from Iron to Uranium Made? 45

Question 11. Is a New Theory of Matter and Light Needed at the Highest Energies? 48

Appendix I. Agency Research Practices and Approaches 49

Appendix II. Technical Glossary 55

Appendix III. Acronyms 62

References 64

Interagency Working Group on the Physics of the Universe 65
We shall not cease from exploration

And the end of all our exploring

Will be to arrive where we started

And know the place for the first time. . . .

 T. S. Eliot

4

The Interagency Working Group on the Physics of 

the Universe (IWG) presents its conclusions on the 

actions necessary to implement the recommendations 

of Connecting Quarks with the Cosmos: Eleven 

Science Questions for the New Century, a 2002 

report of the National Research Council.

The opportunity to gather important new knowledge in 

cosmology, astronomy and fundamental physics stems 

from recent discoveries which suggest that the basic 

properties of the universe as a whole may be intimately 

related to the science of the very smallest known things. 

The properties of stars and galaxies, the existence and 

behavior of black holes, and the way that the universe 

changes with time may be connected to the physics that 

governs elementary particles such as quarks and other 

constituents of atoms.

The IWG was chartered by the National Science and 

Technology Council's Committee on Science to examine 

the investments required in this new area of scientific 

research, and to develop priorities for further action. 

The agencies of the Committee on Science agreed that 

coordination would enable them to provide the most 

beneficial results from such investments. The IWG 

members include representatives from the Department 

of Energy (DOE), the National Aeronautics and 

Space Administration (NASA), the National Science 

Foundation (NSF), the Office of Science and Technology 

Policy (OSTP), and the Office of Management and 

Budget (OMB).

As shown in the list of recommendations on the facing 

page, the immediate priority is heavily weighted toward 

the investigation of “Dark Energy,” a recently discovered 

phenomenon that is causing the universe to expand 

at a greater and greater rate, contrary to the general 

belief of cosmologists and astronomers as recently as 

1998. Dark Energy, when it is adequately explored and 

explained, is expected to have strong implications for 

fundamental physics and perhaps the nature of gravity, 

as well as for the nature, history and potential fate of the 

universe. The IWG recommends three highest priority 

investigations of Dark Energy by means of space and 

ground-based astronomy, which should be enabled by 

coordinated activities of the agencies.

Also ready for immediate investment are certain new 

approaches to the study of Dark Matter, Neutrinos, and 

Proton Decay, which involve physics experiments in 

underground and other ground-based laboratories. This 

work, joining the efforts of two agencies, can illuminate 

the mysterious “Dark Matter,” which composes the 

vast majority of all matter in existence, but whose 

detailed nature is completely unknown to science. 

New and upgraded work on the nature of gravity, 

through massive, high speed computations, as well as 

ground-based and space observatories, is also ready for 

immediate investment. New studies of gravity even bear 

on the possible existence of higher dimensions, once 

thought to be purely the realm of science fiction, but 

now considered seriously by physicists.

Further in the future, to be spelled out in jointly 

formulated roadmaps by the agencies, are new 

departures in the study of the heavy elements and 

nuclear astrophysics, the birth of the universe, high 

density and high temperature physics, and high energy 

cosmic ray physics. In each area, coordinated planning 

at the roadmap stage is essential to maximize the return 

on the Nation’s investment.

The IWG focused its work on the large-scale projects 

needed to support research activities aimed at 

understanding the physics of the universe. These are 

essential elements of a research program, have the most 

significant budget and policy implications, and require 

joint planning to ensure that the Nation develops the 

facilities and programs required to answer the most 

pressing questions without duplication or gaps. The 

IWG recognizes that concomitant investments in theory, 

simulation, data archiving, and user groups are essential 

to reaching the fundamental objective of understanding 

the physics of the universe and expects the participating 

agencies to respond to these requirements in an 

appropriate way.

Each revolution in physics, such as the respective 

discoveries and subsequent explanations of 

electromagnetism, radioactivity, and nuclear forces, has 

produced far-reaching social and industrial consequences 

that were largely unanticipated. It is possible that the 

new physics in Connecting Quarks with the Cosmos, 

when explored and comprehended, will likewise repay 

our initial investments in exploratory research.

Summary
5

Ready for Immediate Investment and 

Direction Known

Dark Energy

* NASA and DOE will develop a Joint Dark Energy 

Mission (JDEM). This mission would best serve the 

scientific community if launched by the middle of the 

next decade. Studies of approaches to the JDEM mission undertaken now will identify the best methodology.

* A high-priority independent approach to place constraints on the nature of Dark Energy will be made by 

studying the weak lensing produced by Dark Matter. 

This is a scientific goal of the ground-based Largeaperture Synoptic Survey Telescope (LSST). Significant technology investments to enable the LSST are 

required, and NSF and DOE will begin technology 

development of detectors, optical testing, and software algorithms leading to possible construction with 

first operations in 2012. NASA will contribute their 

expertise as appropriate. 

* Another priority method to constrain Dark Energy will be to use clusters of galaxies observed 

by ground-based Cosmic Microwave Background 

(CMB) and space-based X-ray observations. A coordinated NSF and NASA effort using this technique 

will provide independent verification and increase the 

precision of the overall measurements.

Dark Matter, Neutrinos, and Proton Decay

* NSF will be the lead agency for concept development for an underground facility. NSF will develop a 

roadmap for underground science by the end of 2004. 

* NSF and DOE will work together to identify a core 

suite of physics experiments. This will include 

research and development needs for specific experiments, associated technology needs, physical specifications, and preliminary cost estimates. 

Gravity

* NSF, NASA, and DOE will strengthen numerical 

relativity research in order to more accurately simulate the sources of gravitational waves.

* The timely upgrade of Laser Interferometer Gravitational wave Observatory (LIGO) and execution of the 

Laser Interferometer Space Antenna (LISA) mission 

are necessary to open this powerful new window on 

the universe and create the new field of gravitational 

wave astronomy.

Next Steps for Future Investments

Origin of Heavy Elements

* DOE and NSF will generate a scientific roadmap for 

the proposed Rare Isotope Accelerator (RIA) in the 

context of existing and planned nuclear physics facilities worldwide.

* DOE and NSF will develop a roadmap that lays out 

the major components of a national nuclear astrophysics program, including major scientific objectives 

and milestones, required hardware and facility investments, and an optimization of large-scale simulation 

efforts. 

Birth of the Universe Using Cosmic 

Microwave Background

* The three agencies will work together to develop 

by 2005 a roadmap for decisive measurements of 

both types of CMB polarization. The roadmap will 

address needed technology development and groundbased, balloon-based, and space-based CMB polarization measurements.

High Density and Temperature Physics

* In order to develop a balanced, comprehensive program, NSF will work with DOE, NIST, and NASA 

to develop a science driven roadmap that lays out the 

major components of a national High Energy Density 

Physics (HEDP) program, including major scientific 

objectives and milestones and recommended facility 

modifications and upgrades. 

* NNSA will add a high energy high-intensity laser capability to at least one of its major compression facilities in order to observe and characterize the dynamic 

behavior of high-energy-density matter. 

* DOE and NSF will develop a scientific roadmap for 

the luminosity upgrade of the The Relativistic Heavy 

Ion Collider (RHIC) in order to maximize the scientific impact of RHIC on High Energy Density (HED) 

physics.

Summary of Recommendations

Acronyms are defined in the text and in Appendix III.
6

To many, research at the forefront of the physical 

sciences can appear as a bewildering array of seemingly 

unrelated activities. Astronomers want to understand the 

behavior of the entire range of objects in the universe 

from planets to stars to galaxies. Cosmologists are 

striving to explain how the universe itself is structured 

and evolved. Particle and nuclear physicists are toiling 

to understand the behavior of subatomic particles that 

have only fleeting existences in our laboratories. The 

tools used in each of these fields are highly specialized 

and appear wildly different from one another. Groundand space-based telescopes actively search the skies. 

Powerful accelerators and colliders create particles, the 

most short-lived of which we detect only indirectly. 

Subterranean detectors sit passively looking for 

particles streaming in from space. Despite all these 

differences, there is an order to the investments the 

Federal Government has made in these fields and their 

tools. In the Connecting Quarks with the Cosmos report, 

the National Research Council (NRC) defined a new 

frontier through a series of eleven questions and clearly 

explained the intellectual unity of seemingly disparate 

fields.

In this report, we show how our current suite of projects 

maps onto those eleven questions, and we plot a path 

to coordinate our future investments in major projects 

most effectively. In compiling a list of the currently 

funded research activities aimed at addressing the eleven 

science questions, we found that more often than not 

projects were funded by multiple agencies, evidence of 

a high degree of joint project execution. The important 

and missing element was the development of processes 

for joint planning across the government and the need 

to look more broadly at the Federal investments in 

science. It was clear that from both the scientific and 

the business perspective, Federal research programs 

in this area require better coordination, and we must 

begin to broaden our scope of interaction. We find 

that, on the one hand, a lack of cross-agency planning 

introduces inefficiency in execution of projects by not 

capitalizing on the expertise wherever it exists across 

the government. On the other hand, we find that a 

lack of planning can potentially introduce imbalance in 

investments in relevant research activities or populate 

budget requests with low priority activities. The efforts 

of the IWG seek to avoid these fates.

Consistent with the President’s Management Agenda, 

the IWG explicitly developed a prioritization process 

to set major goals. These goals are driven by the 

scientific opportunities, independent of agency. The 

IWG fashioned a strategic plan that establishes a broadly 

coordinated program with clear priorities and objectives. 

These objectives serve as the basis for assignments of 

action to each of the participating agencies. As a result, 

all of the objectives are actionable and can be converted 

into specific target activities and specific assignments. 

This enables the concentration of effort and resources to 

the highest priority activities.

In the following sections we present the rationale for the 

development of the specific set of recommendations for 

a Federal research program on the understanding of the 

Physics of the Universe.

In the R&D Investment Criteria section, we discuss how 

this report was based upon the principles embodied in the 

R&D Investment Criteria of the President’s Management 

Agenda. In The Opportunity: Eleven Science Questions 

for the New Century, the IWG examines the status of 

the Federal Government’s current investments aimed at 

answering the NRC’s eleven questions. 

We then made the hard choices to prioritize the new 

facilities needed to make further progress in answering 

these eleven questions. The Programmatic Priorities 

section makes explicit this analysis and explains our 

criteria. The Prioritized Findings and Recommendations 

section gives details and the elements of the strategic 

plan.

As an aid to the reader, we have included several 

appendices. Because each of the programs has 

developed according to its own traditions, we felt it 

important to acknowledge and explain in the Appendix 

on Agency Research Practices and Approaches how the 

different programs participating in the IWG manage 

and evaluate their programs. Often the difficulties 

of interagency cooperation are traceable to these 

differences. We also provide a brief technical glossary 

and a list of acronyms.

A Federal Research Program on the Physics of the Universe

“Consistent with the President’s Management Agenda, it is imperative that, where appropriate, federal 

R&D investments be managed as a portfolio of potentially interconnected activities to optimize scientific 

discovery through interagency coordination of related research areas.”

— Fiscal Year 2005 OSTP/OMB Budget Guidance Memorandum
7

R&D Investment Criteria 

President George W. Bush has made improving the 

management of government programs one of his 

highest priorities. Consistent with the President’s 

Management Agenda, related R&D activities need to 

be managed more effectively across the government 

through careful interagency coordination and planning 

of related research programs.

Concurrent with the release of the Fiscal Year 

2002 budget request, the Administration issued the 

President’s Management Agenda that called for 

a number of government-wide and more targeted 

management reforms. One of these targeted 

management initiatives announced the development 

of R&D Investment Criteria that “will better focus the 

government’s research programs on performance... 

Applied research programs will be better focused on 

achieving well-defined practical outcomes. Basic 

research programs will better target improving 

the quality and relevance of their research. These 

investment criteria will promote our nation’s leadership 

in important science and technology areas.”

In their FY 2005 Interagency Research and 

Development Priorities Memorandum (the “OSTP/

OMB Priorities Memo”), OSTP and OMB issued R&D 

Investment Criteria aimed at improving R&D program 

management and effectiveness.

The Criteria

There are three primary R&D Investment Criteria—

Relevance, Quality, and Performance. Each has 

a prospective and a retrospective component. A 

prospective component describes actions that programs 

must take prior to requesting or allocating research 

funds. A retrospective component describes actions 

programs must take to evaluate the results of their 

research investments. The criteria are briefly described 

below. This report provides, in part, the information 

requested by the R&D Investment Criteria and suggests 

other appropriate venues for obtaining other requested 

information as described below.

Relevance: The R&D Investment Criteria require 

programs to articulate why an investment is important, 

relevant, and appropriate. Agencies are asked to 

explain the methods they use to define program 

direction to ensure relevance and set priorities. 

They should also explain the methods they use to 

retrospectively evaluate program design and relevance 

by periodically reviewing the results of research 

investments already made. Specifically:

* Programs must have complete plans, with clear 

goals and priorities.

* Programs must articulate their potential benefits.

* Programs must document their relevance to 

specific Presidential priorities to receive special 

consideration.

* Program relevance to the needs of the Nation, to 

fields of S&T, and to program “customers” must 

be assessed through prospective external review.

* Program relevance to the needs of the Nation, to 

fields of S&T, and to program “customers” must 

be assessed periodically through retrospective 

external review.

The IWG documents how a subset of research 

investments at the DOE, NASA, and NSF capitalize 

upon the scientific opportunities at the intersection 

of physics and astronomy. Our analysis builds upon 

NASA’s Beyond Einstein program plan and multiple 

NRC and Federal Advisory Committees reports 

and strategic plans. This report as well as NASA’s 

Beyond Einstein program plan responds directly to 

the assessment of scientific opportunity provided in 

the NRC report, Connecting Quarks with the Cosmos: 

Eleven Science Questions for the New Century.

Projects included within the scope of the Physics of the 

Universe plan were required to align specifically with 

and be motivated primarily by at least one of the eleven 

questions. A larger number of important projects were 

examined but were not included within the scope of 

the Physics of the Universe program because they did 

not pass the alignment and motivation test. These 

latter investments are justified based upon other needs 

of the Nation, other fields of science and technology, 

or program “customers.” The IWG undertook a 

prioritization of potential investments. The discussion 

of this prioritization is found in the Recommendations 

section.
8

Quality: The R&D Investment Criteria require 

programs to justify how funds will be allocated to 

ensure the highest quality R&D. Agencies are asked 

to explain the methods they use to prospectively 

review and award funds. They should also explain the 

methods they use to retrospectively review the quality 

of research investments already made. Specifically:

* Programs allocating funds through means other 

than a competitive, merit-based process must 

justify funding methods and document how quality is maintained.

* Program quality must be assessed periodically 

through retrospective expert review.

This report does not address the details whereby 

agencies select and award research funds. The 

retrospective quality and relevance of the collected 

investments that fall within the Physics of the Universe 

program should be periodically evaluated. The IWG 

expects that an appropriately constituted interagency 

advisory committee will be charged with the periodic 

review of the quality and relevance of investments 

made within the scope of the Physics of the Universe 

program. This interagency advisory committee would 

presumably require input or inclusion of representatives 

from the Federal advisory committees that advise the 

individual programs.

It is important to note that review by such a body 

does not preclude review by any agency advisory 

body or external review bodies. In fact, performance 

assessments by these other advisory bodies—High 

Energy Physics Advisory Panel (HEPAP), the Nuclear 

Sciences Advisory Committee (NSAC), and the 

Structure and Evolution of the Universe Subcommittee 

(SEUS) among others—remain essential for the 

evaluation of individual program portfolios, each of 

which contains elements not included within the scope 

of the Physics of the Universe program.

Performance: The R&D Investment Criteria require 

programs to monitor and document how well an 

investment is performing. Agencies are asked to 

explain the methods they use to manage program inputs 

and prospectively set output performance measures. 

They should also be able to retrospectively demonstrate 

performance. Specifically:

* Programs may be required to track and report 

relevant program inputs annually.

* Programs must define appropriate output and 

outcome measures, schedules, and decision 

points.

* Program performance must be retrospectively 

documented annually.

Performance can be documented for various phases 

of the projects within the scope of this report. During 

the R&D phase of major projects, program managers 

should identify the technical issues that require 

resolution prior to a decision to build. Progress 

towards resolving these technical issues can be 

reported. During the construction phase of these 

projects, earned value methods can be used to track and 

report cost, scope and schedule performance. Welldeveloped methods exist within the agencies to review 

the performance of ongoing construction projects. The 

results of these reviews need to be better communicated 

to oversight bodies such as OMB and OSTP.

During the operations phase of these projects, 

performance metrics necessarily have two components: 

(1) low-level, easily reportable, almost “mechanical” 

tracking of countable things such as scheduled 

operating time (e.g., fraction of time beam delivered 

or time shutter actually open), and (2) periodic 

retrospective expert review of a mission’s or facility’s 

scientific impact. An exclusive focus on the easily 

reported metrics can miss the fundamental issue of 

whether a facility is achieving the scientific purposes 

for which it was built. An exclusive focus on the 

retrospective expert review can leave questions about 

the efficient and effective use of public resources 

unanswered.

Nearly all of the facilities included in this report are 

used for experiments that run for more than one year. 

The duration of the experiments is usually governed 

by the statistics required required to establish a 

discovery or differentiate among competing theoretical 

models. After an initial period of learning how to 

operate a new unique facility, “low-level” metrics 

should be developed and reported that demonstrate the 

experiment is making progress towards accumulating 

the required number of events or observations 

necessary to achieve statistical significance, should 

nature behave as predicted. Discovery-oriented 

programs should be judged on whether they advanced 

our understanding of the world, not whether nature 

conforms exactly to our beliefs.
9

Programmatic Priorities 

Based upon an assessment of the current suite of 

existing facilities and the opportunities with the greatest 

potential for scientific advancement, the IWG has 

developed prioritized findings and recommendations 

for programmatic investment to advance the 

opportunities identified in Connecting Quarks with the 

Cosmos. These priorities represent the next steps for 

the Nation and will need to be revisited on a regular 

basis as changes such as available funds, scientific 

advances, and our technological readiness to make 

significant progress change with time.

Setting Priorities:

Step 1: Prioritize the Questions

There are varying levels of activity and investment 

currently being expended to answer each of the eleven 

questions. Moving forward, future investments should 

be aimed at strategically positioning the U.S. scientific 

community to address those issues. To maximize the 

probability that the United States will be strategically 

positioned, the highest priority new investments need to 

be identified. This is never an easy task but one that is 

vital when resources are limited.

The IWG based its prioritization of the eleven 

questions upon an assessment of each question’s fit to 

the following criteria:

- Current potential for scientific advancement

- The timeliness or urgency of each question

- The technical readiness of projects necessary to 

advance the science of each question

- Existence of gaps in the overall suite of projects 

addressing the question.

Those questions classified as the lowest current priority 

for new investment are typically those where the IWG 

believes the United States is adequately invested at the 

present time. Exploitation of existing facilities and 

those under construction is of utmost importance in the 

Physics of the Universe program; however, they are not 

the focus of this prioritization exercise. For example, 

there are a number of particle accelerators and colliders 

operating today where a search for extra dimensions 

can proceed in tandem with other experiments. No 

specialized facility is as yet required to advance the 

search for extra dimensions. The prioritized questions 

are shown in the left column of Table I.

Step 2: Identifying Potential Activities

The foundation for the development of a coherent set 

of recommendations from the IWG was a broad set of 

reports from the National Research Council, reports 

from the DOE-NSF advisory committees HEPAP 

and NSAC, and strategic plans from NASA Space 

Science and DOE Office of Science. This suite of 

reports served as the reference source for the IWG to 

identify projects and activities already recommended 

by the scientific community that can contribute directly 

to answering the eleven questions. In this way, the 

recommendations of the IWG remain consistent with 

the advice and recommendations from the scientific 

community and align with the mission and goals of the 

individual agencies. A list of the source reports used by 

the IWG is given in Table II.

Step 3: Grouping of Related Elements

The next step was to sort the eleven questions based 

upon common programmatic needs or themes. For 

example, some experiments investigating Dark Matter, 

neutrinos, and proton decay will have a common need 

for deep underground laboratory space. Using the 

prioritized ranking of the scientific questions, the IWG 

then applied the additional criterion:

- Programmatic readiness to proceed.

The IWG examined whether the plans and proposed 

facilities were reasonably well developed and 

determined whether a path forward could be identified. 

Programmatic readiness was assessed upon the basis 

of whether a project had been identified, whether the 

science case for such a project has been made, and 

whether R&D on a project is underway.

Where it could not be determined that a path forward 

was known, the IWG recommends that additional roadmapping of future investments is required. Applying 

this additional criterion naturally stratified the 

recommendations into two categories: those program 

areas where the direction or path forward is known 

programmatically, and those where further study is 

required or where current facilities or facilities under 
10

required or where current facilities or facilities under 

construction adequately address opportunities. The 

programmatic investment priority is given in the right 

hand column of Table I.

It should be noted that the dynamical nature of the 

science at this interface, especially at this time of 

great discovery, requires that the efforts of this suite 

of activities be reexamined on a periodic basis. The 

recommendations given here should be viewed as 

the direction that each program within this portfolio 

needs to move now, with the understanding that major 

discoveries have the potential to change our analysis. It 

is also expected that the IWG will continue to develop 

priorities and work to develop joint planning processes 

that seek to manage the activities within this area as 

a single government-wide program. In other words, 

our portfolio of activities will need to evolve to remain 

relevant to the changing frontier of science.

The absence of explicit discussion of the other essential 

aspects of successful programs—such as university 

Table I. IWG Prioritization

Quarks with the Cosmos

Question Programmatic Investment Priority

Ready for Immediate Investment 

 Dark Energy

 Dark Matter

 Gravity

 Neutrinos

Direction Known

 Dark Energy

 Dark Matter, Neutrinos, & Proton Decay

 Gravity

Further Planning and/or R&D Needed

 High Density & Temperature Physics

 Origin of Heavy Elements

 Proton Decay

 The Big Bang

Roadmap Future Investments 

or Exploit Existing Facilities

 Origin of Heavy Elements

 Birth of the Universe using Cosmic Microwave Background

 High Density & Temperature Physics

 High Energy Cosmic Ray Physics Ideas Needed or Investment Adequate

 Cosmic Accelerators

 Extra Dimensions

 New Theories of Light and Matter

Table II. Source Reports for the Interagency Working Group 

on the Physics of the Universe

NRC Reports

Connecting Quarks with the Cosmos: Eleven Science Questions for the New Century

Neutrinos: New Windows on the World

High Energy Density Physics: The X-games of Contemporary Science

Astronomy and Astrophysics in the New Millennium

Federal Advisory Committee Reports

The Science Ahead, The Way to Discovery: The High Energy Physics Advisory Panel Long Range Plan

Opportunities in Nuclear Science: A Long-Range Plan for the Next Decade

Agency Strategic Plans

NASA: Beyond Einstein: From the Big Bang to Black Holes

NASA: Space Science Enterprise Strategy

DOE: Facilities for the Future of Science: A Twenty Year Outlook
11

research groups, education and outreach programs, 

theory, or scientific simulation capabilities—is 

purposeful. We have decided to do so because 

decisions whether to fund the particular projects 

discussed herein have the most significant budget and 

policy implications. Maximizing the scientific return 

in any program requires that such essential elements 

must be considered within the context of the program 

execution plans. In particular, the development of 

large instruments and facilities requires concomitant 

investment in user groups, theory, simulation, and 

data archival activities. These other program elements 

are necessary for the success of every major facility. 

Without attention to and support for such elements, 

the value of each facility is compromised. The 

investment in these areas should be taken as implicit 

within this plan and we have therefore assumed that 

such elements are built into each major program as 

necessary supporting elements. No project plan can 

be considered complete without plans to address all 

essential aspects, including, but not limited to, support 

for university groups, education, outreach, theory, and 

scientific computation.

With Mt. Erebus as a backdrop, personnel inflate the 1 million m3 (28 million cubic foot) balloon which will carry the BOOMERANG 

telescope on its 10 day trip around the Antarctic continent. In order to make its exquisitely sensitive measurements, BOOMERANG was 

lifted above 99% of the atmosphere to an altitude of 35km (120,000 ft). Primary support for the BOOMERANG project came from NSF

and NASA in the United States; the Italian Space Agency, Italian Antarctic Research Programme and the University of Rome La Sapienza 

in Italy; and the Particle Physics and Astronomy Research Council in the United Kingdom. The Department of Energy’s National Energy 

Research Scientific Computing Center provided supercomputing support in the United States.(Photo credit – Phil Mauskopf, University of 

Wales)
12

Prioritized Findings and Recommendations

The recommendations are grouped thematically and 

presented in priority order for future investment. 

Within each theme, only those projects and activities 

that most directly address the theme are included. In 

developing the recommendations for investment the 

IWG sought to clearly identify the steward and major 

participating agencies responsible for developing 

coordinated investments and program plans.

Theme 1: Dark Energy

There are at least three methods to study Dark Energy. 

The most direct and precise approach is to continue to 

use type Ia supernovae as standard candles to map the 

expansion of the universe. A dedicated wide-field-ofview space-based telescope can provide a much larger 

number of precisely measured supernovae over the 

necessary large distance range.

The DOE is funding R&D for a space-based Dark 

Energy mission.

NASA, as part of its proposed Beyond Einstein 

program, has identified a focused mission to study 

Dark Energy. NASA has begun mission concept 

studies, with the goal of determining the optimum 

space-based approach to reveal the nature of Dark 

Energy.

The phenomenon of weak gravitational lensing can 

be used to construct mass maps over a large range 

of distances and, hence, look-back times, to directly 

measure the evolution of mass clustering over about 

half the age of the universe. Understanding the 

evolution of the aggregation of matter (both dark 

and baryonic) via application of this “3-D mass 

tomography” can place strong constraints on the nature 

of the Dark Energy. The telescope must have both a 

large field of view and very high sensitivity to faint 

objects—two of the design goals for the Large-aperture 

Synoptic Survey Telescope (LSST).

The number of clusters of galaxies as a function of 

cosmic time is another sensitive Dark Energy probe. 

The Sunyaev-Zeldovich (SZ) effect—that is, the 

scattering of Cosmic Microwave Background (CMB) 

photons by electrons that are responsible for X-ray 

emission from a galaxy cluster can be used to both find 

clusters in CMB surveys and, combined with X-ray 

measurements by, for example, Constellation-X, used 

to accurately determine the cluster distance. X-ray 

surveys of the sky are another powerful means to find 

clusters over a large distance range.

Findings

* The evidence for Dark Energy is now overwhelming. To make further progress on understanding the underlying physics of this phenomenon requires new capabilities and a concerted 

multi-agency approach.

* Multiple, complementary, and independent 

approaches are necessary for a complete understanding of Dark Energy. A dedicated spacebased experiment to precisely measure the nature 

of the Dark Energy and its evolution over the 

history of the universe is a critical centerpiece to 

this program.

Recommendations

* NASA and DOE will develop a Joint Dark 

Energy Mission (JDEM). This mission would 

best serve the scientific community if launched 

by the middle of the next decade. Studies of approaches to the JDEM mission undertaken now 

will identify the best methodology.

* A high-priority independent approach to place 

constraints on the nature of Dark Energy will 

be made by studying the weak lensing produced 

by Dark Matter. This is a scientific goal of the 

LSST. Significant technology investments to 

enable the LSST are required, and NSF and DOE 

will begin technology development of detectors, 

optical testing and software algorithms leading 

to possible construction with first operations in 

2012. NASA will contribute their expertise as 

appropriate.

* Another priority method to constrain Dark Energy will be to use clusters of galaxies observed 

by ground-based CMB and space-based X-ray 

observations. A coordinated NSF and NASA 

effort using this technique will provide independent verification and increase the precision of the 

overall measurements.
13

Theme 2: Dark Matter, Neutrinos, and 

Proton Decay

Questions about the nature of Dark Matter, the mass 

of the neutrino, and the stability of the proton have 

at their heart the question of the completeness of the 

Standard Model of Particle Physics with concomitant 

implications as to the large-scale structure and 

evolution of the universe. The direct detection of Dark 

Matter, searching for the predicted decay of the proton, 

and determining the absolute mass of the neutrino all 

require an environment that is free of the background 

of cosmic rays, which would overwhelm the signals of 

interest.

The most suitable environment for many of the 

experiments is deep underground, where the surface 

layers of the earth itself provide the necessary 

overburden for shielding. In addition, significant 

savings could be gained since many experimental 

detectors could be used for multiple scientific purposes. 

There are several underground facilities available 

today such as the Soudan Mine in Minnesota, Sudbury 

Neutrino Observatory (SNO) near Ontario, Canada, 

the Gran Sasso in Italy, the Kamioka mine in Japan 

and the Waste Isolation Pilot Plant (WIPP) facility in 

New Mexico. Several other potential sites are currently 

being explored, as well.

The next generation of proton decay experiments does 

not require extreme depths, but does require very large 

volumes of water, and hence, laboratory space. The 

next generation proton decay detectors would need 

a mass approaching the equivalent of a megaton of 

water. Such detectors have a “dual use” and could also 

serve as neutrino detectors for long-baseline neutrino 

oscillation studies and simultaneously allow the study 

of neutrino bursts from supernovae.

The most sensitive experiments require very 

large overburden of rock, while the proton decay 

experiments require laboratory space with large 

volume. Taken as a whole, there exists a synergistic 

case for the development of a laboratory facility with a 

significant overburden of rock to shield the experiments 

from the continual flux of cosmic rays coming from 

space. Consideration of the requirements of future 

generations of experiments further strengthens the 

justification for creation of such a deep underground 

infrastructure. There are several other areas that have 

similar infrastructure needs, including biology, geology, 

and engineering. These are beyond the scope of this 

report but should be considered within the context of 

any suite of underground experiments.

In addition to neutrino experiments using atmospheric 

neutrinos detected by deep underground detectors, 

it is important to use known sources of neutrinos for 

detailed studies of their properties. Neutrinos from 

particle accelerators can be aimed at nearby aboveground detectors or be used for distant long-baseline 

underground experiments. Neutrinos from other 

known sources such as nuclear reactors or the Sun can 

be studied in detail using underground or ground level 

detectors.

Due to the unknown nature of Dark Matter, a 

multi-pronged approach for the next generation of 

experiments is needed. In addition to direct searches 

of Dark Matter candidates using deep underground 

detectors, it is important to use ground-level specialized 

detectors and ground- and space-based telescopes 

to search directly for other types of Dark Matter 

candidates or for gamma rays or neutrinos resulting 

from Dark Matter annihilation. A possible scenario 

is that an underground experiment would be the first 

to detect a Dark Matter candidate. It would then be 

necessary to use a next-generation particle accelerator 

to verify its existence and determine its properties, 

including the determination of whether it could indeed 

account for the approximately 23% of the energymatter content of the universe.

Findings

* The science case for the pursuit of these goals is 

compelling. The detailed planning of a national 

deep underground laboratory and the attendant 

scientific experiments is still at an early stage.

Recommendations

* NSF will be the lead agency for concept development for an underground facility. NSF will 

develop a roadmap for underground science by 

the end of 2004.

* NSF and DOE will work together to identify 

a core suite of physics experiments. This will 

include research and development needs for specific experiments, associated technology needs, 

physical specifications, and preliminary cost 

estimates.
14

Theme 3: Gravity

Two key predictions of General Relativity gravitational 

radiation from moving, interacting masses and the 

existence of Black Holes.

The effort to detect gravitational waves is a primary 

objective of major projects at both NSF and NASA: 

the ground-based Laser Interferometer Gravitationalwave Observatory (LIGO) and the space-based Laser 

Interferometer Space Antenna (LISA). LIGO and 

LISA are complementary in that they view differing 

frequency bands of the gravitational wave spectra 

produced by a variety of cosmic sources. The growing 

NASA LISA effort builds upon the gravitational wave 

community built up by the NSF LIGO efforts over the 

past two decades.

The proof that Black Holes exist has come from a 

combination of space- and ground-based observations. 

NASA’s Chandra X-ray Observatory has demonstrated 

that Black Holes are commonplace in the universe.

Constellation-X (Con-X) will provide a two-orderof-magnitude increase in capability for X-ray 

spectroscopy of cosmic sources and, in doing so, enable 

observation of the effects of gravity in the strong-field 

limit near the horizons of supermassive Black Holes.

Findings

* LIGO, LISA, and Constellation-X together 

provide a powerful and complementary suite 

of tools aimed at the discovery of gravitational 

waves and exploration of the physics of strong 

gravitational fields around Black Holes. This 

has significantly strengthened the gravitational 

physics community. 

* The upgrade of LIGO to achieve a thousand 

times more coverage of the cosmos is expected 

to detect significant numbers of merging stellar 

mass neutron stars and Black Holes, and the core 

collapse of stars.

* Source signal simulations using numerical relativity is essential to predict, identify, and interpret the gravitational wave signals from the large 

variety of sources to be detected by LIGO and 

LISA.

Recommendations

* NSF, NASA, and DOE will strengthen numerical relativity research in order to more accurately 

simulate the sources of gravitational waves.

* The timely upgrade of LIGO and execution of 

the LISA mission are necessary to open this 

powerful new window on the universe and create 

the new field of gravitational wave astronomy.

Theme 4: Origin of Heavy Elements

The approach to understanding the origin and role of 

the heavy elements in the cosmos involves advances 

on several fronts including astronomical observations 

of nucleosythesis signatures in all spectral regions, 

studies of the abundances of elements in stars and 

supernovae, large-scale computer simulations for better 

theoretical interpretation of nuclear processes, and the 

measurement of the properties of exotic nuclei.

Looking forward, the proposed Rare Isotope 

Accelerator (RIA) will be able to specify, control, and 

vary precisely the number of protons and neutrons 

in nuclei in order to study not only the properties 

of individual nuclei, but also the evolution of these 

properties across the nuclear chart. The goal of is to 

achieve a comprehensive, unified theory of nuclear 

structure across the entire landscape of ordinary and 

exotic nuclei, leading to a detailed understanding of 

the processes that led to production of heavy elements. 

The temperatures and particle densities in stellar 

objects and in cataclysmic stellar explosions provide 

an ideal environment to generate the heavy elements, 

whose decay results in the gamma ray emission 

lines that have been observed with astrophysics 

observatories such as the Compton Gamma Ray 

Observatory and INTErnational Gamma Ray 

Astrophysics Laboratory (INTEGRAL).

Large-scale computing simulations are, and will 

continue to be, a vital component in this astrophysics 

arena. Programs such as SCiDAC (Scientific 

Discovery through Advanced Computing) that 

are supported by multi-disciplinary sciences in 

DOE have been successful in making significant 

advances in understanding supernovae explosions 

through coordinated laboratory and university 

efforts. Increasing interagency emphasis on high-end 

computing and cyber-infrastructure is poised to further 

strengthen this effort.
15

Findings

* Existing accelerator facilities with rare isotope 

beams will over the next few years provide 

important information that will advance our 

knowledge of the nucleosynthesis of the lighter 

chemical elements, but a next generation facility will be needed to access the nuclear reactions 

involving the heavier elements.

* Large-scale astrophysics simulation efforts have 

recently been organized and initiated with the 

long-term goals of reproducing the dynamics of 

astrophysics events such as supernovae explosions.

Recommendations

* DOE and NSF will generate a scientific roadmap 

for the proposed Rare Isotope Accelerator (RIA) 

in the context of existing and planned nuclear 

physics facilities worldwide.

* DOE and NSF will develop a roadmap that lays 

out the major components of a national nuclear 

astrophysics program, including major scientific 

objectives and milestones, required hardware 

and facility investments, and an optimization of 

large-scale simulation efforts. 

Theme 5: Birth of the Universe Using Cosmic 

Microwave Background

Measurement of the portion of the polarization of the 

Cosmic Microwave Background (CMB) that was 

caused by primordial gravitational waves offers great 

promise for understanding the inflationary period of 

the universe. The polarization signal due to primordial 

gravitational waves is expected to be at least 100 times 

fainter than the already-detected polarization signal 

caused by early universe density fluctuations.

NASA, as part of its proposed Einstein Probes 

missions, has identified a focused mission to study 

inflation. NASA has undertaken mission concept 

studies to identify promising methodologies for 

a space-based Inflation Probe and to identify the 

necessary technologies for development.

Measuring this faint polarization signal represents 

a significant technical challenge, and a substantial 

detector technology development effort is required 

before a space-based mission can be implemented. 

Ground-based and balloon-borne observations 

are necessary to provide experience with different 

detection schemes (particularly on how to guard against 

false polarization signals) and will provide more 

information about galactic foregrounds. A coordinated 

program of laboratory research, ground-based and 

balloon-borne observations, and finally a space-based 

mission dedicated to CMB polarization will be required 

to get the very best sensitivity to this important 

signature (and probe) of inflation.

DOE, NSF, and NASA support detector technology 

development for submillimeter and microwave 

detectors through their ongoing R&D programs. In 

the near term, ground-based studies from appropriate 

sites and balloon-borne studies from Antarctica will be 

required to prove the detector technology and to study 

the galactic foreground, as well as to exploit CMB 

radiation polarization as a probe of the universe.

Findings

* Successive studies of the CMB with improved 

experimental sensitivity have revealed an increasingly clearer picture of the universe when 

it was 380,000 years old. The temperature 

fluctuations in the CMB data have been used to 

precisely determine the cosmological parameters 

that define our universe.

* A future space-based measurement of the curl 

of the polarization field of the CMB holds the 

promise of detecting the signal of inflation and 

providing tests of the various inflation models 

that have been proposed.

* Ground-based and balloon-borne experiments 

provide initial data to advance and constrain cosmological models, and play a key role in developing detectors and techniques for space-based 

CMB polarization measurements. The current 

Antarctic facilities are inadequate for future 

long-duration balloon missions. 

Recommendations

* The three agencies will work together to develop 

by 2005 a roadmap for decisive measurements of 

both types of CMB polarization. The roadmap 

will address needed technology development and 

ground-based, balloon-based, and space-based 

CMB polarization measurements.
16

Theme 6: High Density and Temperature 

Physics in the Laboratory

High Energy Density Physics (HEDP) in the laboratory 

can be used to explore fundamental physical processes 

that occur under extreme high energy density, 

and this provides a direct probe of the conditions 

found in exotic locations in the universe. These 

cosmic locations range from supernovae and stellar 

atmospheres of nearby stars to the first moments of the 

birth of the universe. Laboratory measurements are 

also essential to interpreting many space- and groundbased astronomical observations. The study of matter 

under extreme conditions represents the opportunity to 

explore new physical regimes in many fields, including 

plasma physics, nuclear physics, materials science 

and condensed matter physics, atomic and molecular 

physics, fluid dynamics and magneto-hydrodynamics.

Such experimental regimes are now becoming 

increasingly accessible with the development of major 

new and upgraded facilities, such as the National 

Nuclear Security Administration’s Omega, Z, and 

National Ignition Facility (NIF), and continuing 

advances in the development of laser and pulsed power 

systems suitable for university laboratory settings. 

Continuing rapid advances in laser technology and 

the resulting availability of compact, high-intensity 

laser sources are major factors in making this exciting 

and rapidly changing field accessible to university 

researchers.

Another opportunity to study matter at high energy and 

density exists at the Relativistic Heavy Ion Collider 

(RHIC) which was designed to create and study the 

quark-gluon plasma (QGP), a state of matter that 

existed during the first moments of the birth of the 

universe. RHIC probes the evolution of the QGP in the 

High-Energy-Density environment formed when two 

massive nuclei collide. An increase in beam luminosity 

would enable even more detailed studies of the QGP, 

thus completing a comprehensive characterization of 

this new state of matter and gaining new insight into 

the early phases of the universe.

Interpretation of the complex and exotic collective 

phenomena occurring in matter at extreme conditions 

requires high-end computation to provide numerical 

simulations needed to interpret the experiments.

Findings

* HEDP is an emerging field that provides crucial 

measurements that are relevant to interpreting 

astrophysical observations of the universe. The 

field has great promise that should be better 

coordinated across the various Federal agencies 

to capitalize on the emerging opportunities.

Recommendations

* In order to develop a balanced, comprehensive 

program, NSF will work with DOE, NIST, and 

NASA to develop a science driven roadmap 

that lays out the major components of a national 

HEDP program, including major scientific objectives and milestones and recommended facility 

modifications and upgrades.

* NNSA will add a high energy high-intensity laser 

capability to at least one of its major compression facilities in order to observe and characterize the dynamic behavior of high-energy-density 

matter.

* DOE and NSF will develop a scientific roadmap 

for the luminosity upgrade of RHIC in order to 

maximize the scientific impact of RHIC on HED 

physics.

Theme 7: High Energy Cosmic Ray Physics

In order to fully understand the production and 

acceleration mechanisms, a complementary and 

coordinated suite of experiments on the ground and 

in space is necessary. The current approach includes 

ground-based and space-based detectors under 

consideration by all three agencies. It is important that 

the current program be completed as planned. The 

current suite of detectors under construction includes 

the Gamma Ray Large Area Space Telescope (GLAST) 

and the Very Energetic Radiation Imaging Telescope 

Array System (VERITAS) which will operate in 

complementary energy ranges.

The ground-based Pierre Auger cosmic ray detector 

array is under construction in the Mendoza Province 

of Argentina. DOE and NSF collaborate on this 

experiment, along with several foreign partners. Due 

to the economic situation in Argentina, funding for the 

Pierre Auger array may be compromised. A similar 
17

array in the northern hemisphere has been discussed. 

The consideration of the science case for this array will 

take place after the initial data from the Auger array is 

analyzed.

ICE CUBE is a cubic kilometer array to study high 

energy neutrinos that is currently under construction 

at the South Pole. It is being developed with support 

from NSF and international partners. Ice Cube will 

offer a new approach to studying very high energy 

cosmic rays and associated acceleration processes.

Findings

* DOE, NSF, and NASA are developing a coordinated broad program of ground-, balloon-, and 

space-based facilities to study the highest energy 

messengers from the universe and the particle 

acceleration processes that produce them.

Recommendations

* DOE and NSF will work together to ensure that 

the Pierre Auger southern array is completed and 

will jointly review the results from the Auger array after the first full year of operations in order 

to consider plans for a possible northern array.
18

The Opportunity: 

Eleven Science Questions for the New Century

“The answers to these questions strain the limits of human ingenuity, but the questions themselves are 

crystalline in their clarity and simplicity . . .”

The Eleven Questions Identified by the Connecting Quarks with the Cosmos Report

 1. What is Dark Matter?

 2. What is the Nature of Dark Energy?

 3. How Did the Universe Begin?

 4. Did Einstein Have the Last Word on Gravity?

 5. What are the Masses of the Neutrinos and How 

Have They Shaped the Evolution of the Universe?

 6. How do Cosmic Accelerators Work and What are 

They Accelerating?

 7. Are Protons Unstable?

 8. What Are the New States of Matter at Exceedingly High Density and Temperature?

 9. Are There Additional Space-Time Dimensions?

10. How Were the Elements from Iron to Uranium 

Made?

11. Is a New Theory of Light and Matter Needed at 

the Highest Energies?

How did the universe come to appear as it does today? 

What is it made of? What is its fate? These easyto-ask questions are not so simple to answer. Recent 

discoveries have lead scientists to conclude that 95% 

of our universe is composed of matter and energy that 

has no earthly resemblance. The stuff we are made of 

makes up merely five percent of the universe! Dark 

Matter, matter or particles that we cannot see, makes 

up 25% of our universe. Astronomers, looking at the 

details of the motion of galaxies, have demonstrated 

its existence conclusively. Dark Energy, a mysterious 

energy field that is pushing the universe apart at an 

accelerating rate, comprises 70% of our universe. 

The existence of Dark Matter and Dark Energy are 

astronomical discoveries. The elucidation of their 

properties is the domain of particle physics. In order to 

unravel the mystery, the two will need to work together. 

The questions "What is Dark Matter?" and "What is 

Dark Energy?" are only two of the driving questions at 

this intersection.

But, as if this where not enough, not only have we 

discovered that the universe is comprised largely of 

particles and fields we don’t understand, but we also 

have an unsatisfying inability to explain how nature 

produced much of what we do see on an everyday 

basis. To date, there is not a good explanation for how 

the heavy elements—things such as copper, tin, silver, 

or gold—came to be. They exist on earth, and we infer 

their existence in the light emitted from stars, but we 

are unable to understand how they were formed.

At the other extreme, in the study of the nature of 

elementary particles, physicists have speculated that 

there must exist additional space-time dimensions that 

Quotations are taken from Connecting Quarks with the Cosmos.
19

are, as yet, undetected. If extra dimensions exist, the 

effects would most probably be felt on the largest scales 

of the universe, and would have played an integral part 

in the formation of the universe at its earliest stages. 

Effects would also be evident in experiments that study 

the nature of elementary particles. Astronomers and 

physicists will need to work together to search for their 

existence and understand their effects.

The most ubiquitous force of nature, gravity, remains 

an enigma. The theory of gravitation, embodied in 

Einstein’s theory of General Relativity, is the least 

tested of the modern theories of physics. The only 

tests of the theory to date come from measuring only 

very tiny differences from the predictions of Newton’s 

laws. Yet this theory is the basis for our model of the 

large-scale structure and evolution of the universe, and 

there are much more profound predictions that are now 

within our reach experimentally. The detailed studies 

of the nature of black hole and the measurements of 

gravitational radiation will provide the first true tests of 

General Relativity.

In the 2002 National Research Council report entitled 

Connecting Quarks with the Cosmos: Eleven Science 

Questions for the New Century, a new frontier for 

discovery at the intersection of physics and astronomy 

was clearly presented. The eleven science questions 

are simple and clear, yet "among them are the most 

profound questions that human beings have ever posed 

about the cosmos." The answers to these questions 

have profound implications about our understanding of 

our world, the universe, and how it came to be and its 

ultimate fate. 

The composition of the universe is now believed to be made of 5% visible matter and 95% dark energy and dark matter (figure courtesy 

of Stanford Linear Accelerator Center)
20

Question 1. What is Dark Matter?

“Astronomers have shown that the objects in the universe from galaxies a million times smaller than ours 

to the largest clusters of galaxies are held together by a form of matter that is not what we are made of 

and that gives off no light. This matter probably consists of one or more as-yet-undiscovered elementary 

particles, and aggregations of it produce the gravitational pull leading to the formation of galaxies and 

large-scale structures in the universe. At the same time these particles may be streaming through our 

Earth-bound laboratories."

Scientific Significance: One of the most important 

scientific questions at the beginning of the 21st Century 

is “What is Dark Matter?” Dark Matter—matter that 

neither emits nor absorbs light and that interacts very 

weakly with ordinary matter—holds the universe 

together. Its nature is a complete mystery. Despite the 

wondrous advances of science over the last century, 

we have yet to identify the majority component of the 

matter in the universe. The working hypothesis is that 

it is composed of elementary particles left over from 

the Big Bang that created the universe. The leading 

candidates for the Dark Matter are new particles whose 

existence is predicted by theories that go beyond the 

Standard Model of Particle Physics. Showing that one 

or more of these particles comprise the Dark Matter not 

only would answer a key question in cosmology, but 

also would shed new light on the fundamental forces 

and particles of nature. Note that this section will focus 

approaches to detect so-called “cold Dark Matter,” 

which means that particles of this type are not moving 

at great speeds. Other approaches to both cold and hot 

Dark Matter are described in later sections on neutrinos 

and the Cosmic Microwave Background (CMB) 

radiation.

The Sloan Digital Sky Survey (SDSS) is two separate surveys in one: galaxies are identified in 2D images (right), then have their distance 

determined from their spectrum to create a two-billion lightyears deep 3D map (left) where each galaxy is shown as a single point, the 

color representing the luminosity—this shows only these 66,976 out of 205,443 galaxies in the map that lie near the plane of Earth’s 

equator.
21

Measurement Methods: There are four strategies for 

studying (cold) Dark Matter.

1) Astronomical observations can detect its presence 

through the dynamical studies of the motions of stars, 

galaxies, and X-ray emitting hot gas in clusters of 

galaxies. These have provided the first convincing 

evidence for the existence of Dark Matter and can be 

used to trace its location and properties. For example, 

a large mass of Dark Matter can distort the image of 

more distant astronomical objects by gravitational 

lensing, a consequence of the distortion of space-time 

predicted by Einstein’s general theory of relativity. 

Gravitational lensing can be studied by means of 

astronomical surveys over large parts of the sky.

2) The direct detection of Dark Matter particles is 

possible through highly specialized detectors designed 

to detect directly the extremely weak signal of a rare 

Dark Matter interaction with a massive detector, 

coupled with strong suppression of background signals 

that could overwhelm the signal of interest. This 

normally requires placing a Dark Matter detector deep 

underground in order to shield it from cosmic rays 

that would confound the search for Dark Matter. One 

can also search for Dark Matter candidates that should 

have been produced in the Big Bang using high-Q 

tunable microwave cavities in a magnetic field. The 

next generation experiments will use Superconducting 

Quantum Interference Device (SQUID) amplifiers.

3) Gamma rays or neutrinos resulting from annihilation 

of Dark Matter particles by their antimatter 

counterparts may be detected by astronomical 

telescopes. This process may take place in the core 

of the Sun or surrounding the center of the Galaxy, 

where Dark Matter and anti-Dark Matter might be 

concentrated by strong gravitational fields.

The ring of distorted images of a galaxy is the result of “gravitational lensing” by a cluster of galaxies between it and us. Studying the distortions gives valuable information about the distribution of dark, unseen matter in the cluster. The ring, a prediction of General Relativity, 

is called an “Einstein Ring.” Credit: NASA/Hubble Space Telescope (HST)
22

Project Name Steward

Participating 

Agencies Scientific Approach Status

Sloan Digital Sky 

Survey

Sloan Foundation 

(Private)

DOE - High Energy 

Physics

NSF - Astronomy

NASA - Space 

Science

Study large scale distribution 

of matter (e.g., galaxies in the 

universe)

Ongoing 

Project

Cryogenic Dark 

Matter Search 

(CDMS)

DOE - High Energy 

Physics

NSF - Physics

NSF - Astronomy

Direct detection of Dark 

Matter particles

Ongoing 

Project

4) One can also try to create Dark Matter particles by 

colliding particles of ordinary matter in high-energy 

particle accelerators. It is possible that Dark Matter 

may be comprised of exotic forms of matter that lie just 

beyond the reach of existing accelerators. The lowestenergy particles from the theory of “supersymmetry” 

are candidates.

Current Projects: The ground-based Sloan Digital Sky 

Survey (SDSS) continues to collect data on the largescale distribution of galaxies and quasars, which can 

be used to investigate the amount and effects of Dark 

Matter in the universe. 

(http://www.sdss.org/sdss.html)

The Cryogenic Dark Matter Search (CDMS) and 

its follow-on, CDMS-II, aim to measure the energy 

imparted to detector nuclei through collisions of Dark 

Matter particles and atoms in the crystals of highly 

sensitive detectors. 

(http://cdms.berkeley.edu/experiment.html)

In addition to these focused projects, the creation of 

potential Dark Matter particles is one of the goals of 

the study of particle physics at the world’s highest 

energy accelerators, for example at the Tevatron at 

Fermilab and the soon to be completed Large Hadron 

Collider at the Center for European Nuclear Research 

(CERN). Further, astronomical telescopes are capable 

of providing studies of the effects of Dark Matter. 

These include the Hubble Space Telescope and groundbased telescopes, such as the Keck Telescope, which 

can detect the dynamical effects of Dark Matter, and 

GLAST and VERITAS, which will be able to detect 

gamma rays resulting from annihilation of Dark Matter 

particles.
23

Question 2. What is the Nature of Dark Energy?

“Recent measurements indicate that the expansion of the universe is speeding up rather than slowing down. 

This conclusion goes against the fundamental idea that gravity is always attractive. This discovery calls 

for the presence of a form of energy, dubbed “Dark Energy,” whose gravity is repulsive and whose nature 

determines the destiny of our universe."

Scientific Significance: Two independent lines of 

evidence indicate the presence of a new form of 

energy pervading the universe that accounts for over 

two-thirds of the contents of the universe. This “Dark 

Energy” is causing the expansion of the universe to 

speed up, rather than to slow down, as was previously 

expected. Resolving the nature of Dark Energy is one 

of the most pressing questions facing both physics and 

cosmology and will no doubt lead to progress in our 

fundamental understanding of both.

Measurement Methods: There are at least three 

methods to investigate Dark Energy.

Because of Dark Energy’s diffuse nature, the best 

methods to probe its properties rely upon its effect 

on the expansion rate of the universe and how it 

influenced the formation of large-scale structure, the 

web of galaxies and clusters we see today. The use of 

distant, or high-redshift, supernovae (redshift 0.5-1.8) 

as a cosmic ruler led to the discovery of the cosmic 

expansion speed-up. Such supernovae have great 

promise for shedding light on the nature of the Dark 

Energy. Realizing this promise will require a new 

class of wide-field telescopes to discover and follow 

up thousands of supernovae, as well as independent 

analysis of type Ia supernovae to better establish the 

degree to which they are standard candles.

Independent measurements of the Cosmic Microwave 

Background (CMB), the afterglow of the birth of the 

universe, also indicates the presence of an exotic form 

of energy pervading the universe.

The evolution of galaxy clusters provides an 

independent probe of Dark Energy. Clusters can be 

detected out to redshifts as large as 2 or 3 through 

X-ray surveys, through large-area radio and millimeter-

[Left] - A Hubble Space Telescope image of a portion of the Hubble Deep Field North as originally photographed in 1995 with the 

Wide Field Planetary Camera 2 (WFPC2). [Right] - A composite image of the same field as imaged by Hubble’s Advanced Camera for 

Surveys (ACS), combined with the original WFPC2 image. The ACS observations were made in May and June 2002. The red spot is 

the glow of a very distant supernova captured exploding in the field. The supernova is estimated to be eight billion light-years away. 

The supernova appears deep red in this composite image because it was photographed by the ACS at far-red wavelengths. Distant 

supernovae are used by astronomers to fill in the blank region where the universe’s rate of expansion switched from deceleration due to 

gravity to acceleration due to the repulsive force of “Dark Energy.”
24

wave surveys using a technique known as the SunyaevZel’dovich (SZ) Effect, and through gravitational 

lensing. Con-X, for example, will be able to determine 

the redshifts and masses of the clusters.

Counts of galaxy clusters, high-redshift supernovae, 

weak-gravitational lensing, and the Cosmic 

Microwave Background (see Question 3) all provide 

complementary information about the existence and 

properties of Dark Energy.

Current Projects: There are many ongoing studies 

of Type Ia supernovae using existing facilities such 

as the Hubble Space Telescope (HST) and telescopes 

at the Cerro Tololo Inter-American Observatory and 

Keck Observatories. These will provide additional 

measurements of a few hundred supernovae.

There are two ground-based telescope projects under 

construction that use the Sunyaev-Zel'dovich effect 

technique. The 8m South Pole Telescope (SPT) will 

perform a large-scale survey for distant galaxy clusters 

to study Dark Energy through the SZ effect. 

(http://astro.uchicago.edu/spt/)

The Atacama Cosmology Telescope (ACT) will do a 

large-area survey of the sky to map out the formation of 

cosmic structure over a wide range of redshift. Among 

its goals is to find and study galaxy clusters using the 

SZ effect.

This graph plots the size of the universe over time as measured 

by the Hubble telescope observations of exploding stars, called 

supernovae, at various distances from Earth. Hubble’s study of 

exploding stars several light-years from Earth [white objects at 

far right of curve] set the stage for observations of more distant 

supernovas [white objects at far left of curve].

Supernovae are used to map the expansion of the universe—

the rate at which galaxies are moving apart. Several exploding 

stars discovered four years ago provided evidence that the 

cosmos was accelerating. These objects looked dimmer than 

expected because they were hurling away from Earth at faster 

speeds. The faraway supernova at far left, residing 10 billion 

light-years from Earth, appears brighter than astronomers predicted. This finding indicates that the supernova is so far away 

it existed at a time when the cosmos was slowing down.

Project Name Steward

Participating 

Agencies Scientific Approach Status

SPT NSF - Office of 

Polar Programs Sunyaev-Zel'dovich Effect Under Construction

ACT NSF - Astronomy NSF - Physics Sunyaev-Zel'dovich Effect Under 

Construction

(http://www.hep.upenn.edu/~angelica/act/index.html)
25

Question 3. How Did the Universe Begin?

“There is evidence that during its earliest moments the universe underwent a tremendous burst of 

additional expansion, known as inflation, so that the largest objects in the universe had their origins in 

subatomic quantum fuzz. The underlying physical cause of this inflation is a mystery.”

Scientific Significance: An amazing chain of events 

was unleashed by the Big Bang, culminating today 

some 13.7 billion years later in molecules, life, planets, 

and everything we see around us. One of the great 

successes of cosmology over the past two decades 

has been the development and initial testing of the 

“inflationary paradigm,” which provides an explanation 

for the large size and uniformity of the universe as well 

as the origin of the lumpiness that led to galaxies and 

clusters of galaxies—that is, how the universe evolved 

from a primeval fog to pristine hierarchy.

The inflationary paradigm, describing how the universe 

expanded from an atomic scale to a visible scale in 

a fraction of a second, is supported by observations 

of tiny fluctuations in the intensity of the Cosmic 

Microwave Background (CMB) radiation, the 

afterglow of the birth of the universe.

Measurement Methods: Space-based, balloon-based, 

and ground-based observations of the CMB provide 

the most direct probe of the Big Bang. The recent 

Wilkinson Microwave Anisotropy Probe (WMAP) 

results have elevated this field to a new level by using 

high quality CMB data to derive the cosmological 

parameters that define our universe.

The measurements of the CMB detail a radiation 

source of unusual and remarkable features. The 

CMB radiation is isotropic on both large and small 

angular scales to a higher degree than any other source 

in the universe and exhibits only little in the way 

of polarization. The spectrum of the CMB is well 

characterized as an ideal blackbody, or thermal, source 

with only minor deviations. In short, the CMB 

radiation exhibits all of the characteristics 

of what one would expect from a 

simple model for the remnant of a 

homogeneous and structureless primeval explosion.

CMB polarization (the 

degree to which light 

waves are aligned) holds 

the promise of revealing unique 

features of the early universe, for 

specific phenomena will polarize 

light—for example, magnetic 

NASA's WMAP satellite.

The Wilkinson Microwave Anisotropy Probe captured this image of the infant universe, light that was emitted 380,000 years after the Big 

Bang. The light has been stretched in wavelength, by the expansion of the universe, from the visible to the microwave. 

Credit: NASA/WMAP.
26

The figure indicates some major periods in our history: the mysterious “Planck era” at the earliest time (not shown); a period of inflation 

at the neck of the goblet that explains the uniformity we see today; a time at which the strong, weak and electromagnetic forces stop 

being equal (not shown); a period when the excess of particles over anti-particles came about (nor shown); the time, three minutes, when 

the nuclei of the light elements were made; the time, 380,000 years from the recent WMAP results, at which electrons were captured by 

nuclei and the universe became transparent to light because there were no charged particles to get in its way; the period of galaxy formation; and here we are today — a time to solve ageless mysteries.
27

WMAP maps are being used to accurately establish the 

age of the universe, to measure the composition of the 

universe, and to determine the epoch of the first star 

formation.

(http://map.gsfc.nasa.gov/)

The Cosmic Background Imager (CBI) is a specialpurpose radio telescope consisting of 13 1-meter 

diameter elements and is designed to study the 

polarization anisotropy of the Cosmic Microwave 

Background. The CBI has produced the highest 

resolution images of the CMB to date, showing 

Project Name Steward

Participating 

Agencies Scientific Approach Status

Degree Angular 

Scale Interferometer 

(DASI)

NSF - Office of 

Polar Programs

Instrument at South Pole to 

measure temperature and 

polarization anisotropy of 

CMB radiation

Ongoing 

Project

Wilkinson 

Microwave 

Anisotropy Map 

(WMAP)

NASA - Office of 

Space Science

Space mission to map 

temperature fluctuations in the 

CMB radiation

Ongoing 

Project

Cosmic Background 

Imager (CBI) NSF - Astronomy

Instrument in Atacama Desert 

to measure polarization anisotropy of CMB

Ongoing 

Project

Planck European Space 

Agency 

NASA - Office of 

Space Science

Space mission to image the 

temperature fluctuations in the 

CMB radiation

Under 

Construction

This simulation of the CMB shows the curl of the polarization 

field by gravitational waves as long as the universe.

fields, electron scattering, or gravitational radiation. 

This polarization has been detected convincingly in a 

small region of the sky using the Degree Angular Scale 

Interferometer (DASI) telescope at the South Pole. 

The observation of the linear polarization of the CMB 

by WMAP has revealed that the first stars turned on 

only 200 million years after the birth of the universe. 

This is just a start. Measuring the curl of the CMB 

polarization with increased sensitivity may reveal the 

signature of gravitational waves produced during the 

inflationary epoch. This is a difficult measurement, but 

the payoff is great: Measuring the CMB polarization in 

essence triples the information we can obtain about the 

earliest moments, and it exploits the full information 

available in this most important relic of the early 

universe. The long-range goal of polarization studies 

is to detect the consequences of gravitational waves 

produced during the inflationary epoch. This campaign 

will be carried out with polarization sensitive CMB 

detectors on the ground, aboard balloons, and in space.

Current Projects: There are currently two on-going 

projects. The Degree Angular Scale Interferometer 

(DASI) is a 13-element interferometer designed to 

measure temperature and polarization anisotropy of 

the CMB radiation over a large range of scales with 

high sensitivity. The instrument operates from the NSF 

Amundsen-Scott South Pole station. 

(http://astro.uchicago.edu/dasi/)

WMAP is the highly successful Wilkinson Microwave 

Anisotropy Probe, a space mission that is mapping 

the temperature fluctuations in the cosmic microwave 

background with unprecedented sensitivity. The 
28

fluctuations corresponding to the seeds of present day 

clusters of galaxies.

Planck is a European Space Agency mission that is 

planned for a 2007 launch. Planck will image the 

anisotropies of the cosmic microwave background with 

high sensitivity and spatial resolution. Planck will 

map temperature fluctuations in the cosmic microwave 

background over a broad wavelength band with 

unprecedented spatial resolution. Planck will place 

fundamental constraints on models for the origin and 

evolution of large scale structure in the universe. 

DASI is a 13-element interferometer designed to measure temperature and polarization anisotropy of the Cosmic Microwave Background 

(CMB) Radiation over a large range of scales with high sensitivity. The instrument operates from the NSF Amundsen-Scott South Pole 

station. Funding for DASI comes from the NSF Office of Polar Programs. The Center for Cosmological Physics (CfCP) provides additional support at the University of Chicago. (Photo Credit – John Yamasaki and the DASI Collaboration, 2002)

(http://astro.estec.esa.nl/SA-general/Projects/Planck/)
29

detection has become a compelling frontier of physics 

with its origins in the theory of General Relativity, 

created by Albert Einstein early in 1915. Gravitational 

waves, when detected, will be a radically new 

messenger from the cosmos. Such waves are produced 

before light is generated in phenomena such as star 

explosions or Black Hole mergers and, unlike light, can 

penetrate through the thickest of “fogs” surrounding 

these cataclysmic events.

Measurement Methods: There are at least eight 

approaches to gravitational physics and gravitational 

wave astronomy: resonant bar detectors, large 

interferometer detectors, mapping of radiation 

from near the event horizons of Black Holes, 

precision laboratory measurements at distances 

below a millimeter, laboratory and space tests of the 

equivalence principle, lunar laser ranging experiments, 

numerical relativity, and formal theory, including 

string theory and other approaches to quantum gravity. 

In addition, such approaches as the measurement of 

Question 4. Did Einstein Have the Last Word on Gravity?

“Black Holes are ubiquitous in the universe, and their intense gravity can be explored. The effects of 

strong gravity in the early universe have observable consequences. Einstein’s theory should work as well 

in these situations as it does in the solar system. A complete theory of gravity should incorporate quantum 

effects — Einstein’s theory of gravity does not — or explain why they are not relevant."

Scientific Significance: Of the four known 

fundamental forces (electromagnetic, weak, strong, 

and gravitational), the gravitational force is the most 

enigmatic. Whereas the electromagnetic, weak, and 

strong forces are well defined by quantum mechanics, 

gravity is the odd man out. It is by far the weakest 

force, yet it holds galaxies together, ignites the fusion 

reaction in stars, and curves space within Black Holes 

so severely that light is trapped.

Einstein tackled gravity in his theory of General 

Relativity, which predicts ripples in space-time called 

gravitational radiation and also Black Holes, which are 

purely defined by gravity. Studying gravity at its most 

extreme—close to the event horizon, a Black Hole’s 

border of no return, and in the creation of gravitational 

waves—provides the best test of General Relativity and 

a better understanding of gravity.

Although the universe should be filled with 

gravitational waves from a host of cataclysmic 

cosmic phenomena, including Black Holes, we have 

never detected a gravitational wave and measured 

its waveform. For this reason, gravitational wave 

Black Holes are ubiquitous in the universe as demonstrated by 

the Chandra X-ray Observatory. All of the X-ray sources seen in 

this 12-day exposure, the deepest X-ray image of the universe 

ever taken, are powered by Black Holes at the cores of active 

galaxies and quasars. Many of them can be seen only with an 

X-ray telescope because they are shrouded by dust and invisible to optical telescopes

The LIGO facility in Hanford, WA.
30

CMB polarization (see last section) and astronomical 

observation of neutron star binaries (produced the first 

indication of gravitational radiation) are relevant.

The frontiers of gravitational wave science are now 

defined by: the interferometric approaches on the 

ground (Laser Interferometer Gravitational wave 

Observatory, LIGO) and in space (Laser Interferometry 

Space Antenna, LISA); laboratory measurements in 

the micron range; planned missions to map matter 

near the event horizon of Black Holes (ConstellationX); numerical relativity to compute wave forms of 

gravitational waves to be measured; and formal theory 

to better understand gravity as part of a unified theory 

of fundamental forces. LIGO has just begun its search 

for gravity waves, and its upgrade to increase its 

coverage of the universe by a factor of 1000 has just 

been proposed. LISA and Constellation-X, missions 

proposed in the President’s FY 2004 budget, will study 

Black Holes in great detail.

Interpretation of these data requires substantial 

advances in our understanding of photo-ionized 

plasmas and their X-ray emissions. Laboratory highenergy-density facilities are needed to develop the 

required understanding of the plasma physics in the 

vicinity of Black Holes. Furthermore, the accretion 

disks around Black Holes may be radiation-dominated 

plasmas, in which the energy density of the radiation 

exceeds that of the matter. High-energy-density plasma 

devices will contribute to the understanding of this 

exotic state of matter (see under Question 8).

Current Projects: LIGO is the Laser Interferometer 

Gravitational-wave Observatory, a facility dedicated 

to the detection of cosmic gravitational waves and the 

measurement of these waves for scientific research. 

It consists of two widely separated installations, at 

Hanford, WA, and at Livingston, LA, operated in 

unison as a single observatory. LIGO searches for 

waves of higher frequency, compared to LISA. 

(http://www.ligo.caltech.edu/)

GPB is Gravity Probe B, an orbiting gyroscope that 

is planned for launch, is sensitive enough to directly 

detect two predictions of Einstein’s theory of General 

Relativity: the geodetic effect (the warping of spacetime due to the Earth’s mass) and frame dragging (the 

twisting of space-time due to the rotation of the Earth). 

(http://einstein.stanford.edu/)

Project Name Steward

Participating 

Agencies Scientific Approach Status

Laser Interferometer 

Gravitational wave 

Observatory (LIGO)

NSF - Physics

International 

collaboration with 

eight countries

Detect gravitational waves 

directly using laser 

interferometers

Ongoing 

Project

Gravity Probe B NASA - Office 

of Space Science

Gravity measurements using a 

gyroscope in space

Under 

Construction

The detection of gravitational wave in the next decade would 

not only confirm one of the most basic prediction of Einstein's 

Theory of General Relavity, but also provide a new window on 

the universe.

Constellation-X

The Constellation-X Observatory will investigate black holes, 

Einstein’s theory of General Relativity, galaxy formation, the 

evolution of the universe on the largest scales, the recycling of 

matter and energy, and the nature of "dark matter."
31

Question 5. What Are the Masses of the Neutrinos 

and How Have They Shaped the Evolution of the Universe?

“Cosmology tells us that neutrinos must be abundantly present in the universe today. Physicists have found 

evidence that they have a small mass, which implies that cosmic neutrinos account for as much mass as do 

stars. The pattern of neutrino masses can reveal much about how Nature’s forces are unified and how the 

elements in the periodic table were made."

Scientific Significance: Among the many actors in the 

areas of elementary particle physics and messengers 

from the cosmos, neutrinos have recently taken center 

stage. One of the most significant observations in 

years has been that neutrinos can oscillate, or change, 

from one type to another as they travel. There are two 

main reasons why this is important: first, the fact that 

neutrinos oscillate means that they have mass. This 

mass is small, but the overwhelming preponderance 

of neutrinos in the universe means that a significant 

amount of Dark Matter is in the form of neutrinos 

traveling essentially at the speed of light (hot Dark 

Matter). Second, neutrinos are not “supposed” to have 

mass in the Standard Model of Particle Physics, so 

herein lies a hint at the next higher level of theoretical 

understanding. Oscillation has begun a whole new 

scientific thrust to understand the properties of the 

neutrino “sector,” much like the campaign in the last 

twenty years or so in the quark sector. New questions 

are arising. What is the degree of charge-parity (CP) 

violation in the neutrino sector? (CP violation may 

explain why there is more matter than antimatter.) Are 

neutrinos their own antiparticles? Are there unknown 

types of neutrinos, such as sterile neutrinos? Neutrinos 

also pass through the universe mostly unaffected, so 

that they are useful messengers from distant cosmic 

citizens. This characteristic will be discussed in 

connection with the next question.

MINOS Far Detector in Soudan, MN. The mural on the wall was painted by a local artist to represent the physics of neutrinos.
32

Measurement Methods: One characteristic defines 

all experimental approaches for detecting and studying 

neutrinos: neutrinos interact only very weakly with 

matter. They can pass through the earth, the Sun, and 

whole galaxies unscathed. However, they do interact 

through the “weak interaction,” occasionally striking, 

for example, one proton out of trillions upon trillions 

traveling through thousands of miles of solid earth. 

Such a collision can be detected, often as a flash of 

light, if the detector volume is large enough and the 

background counts in the detector are low enough. 

Basically, this requires very large detectors (kilotons to 

gigatons of detector medium, such as water or ice) and 

a location well shielded from cosmic rays, usually deep 

underground.

These difficulties are mitigated when one knows 

when and from where the neutrinos are coming—for 

example, from pulsed sources such as accelerators 

or from known continuous sources such as the Sun. 

Long baseline experiments involving neutrinos from 

accelerators can do with less shielding from cosmic 

rays, but multiple uses of the large detectors is 

gained when they are placed deep underground. As 

for the issue of the absolute mass of the neutrinos, 

understanding this requires not detecting incoming 

neutrinos, but rather the observation of neutrino-less 

double beta decay, a very weak process occurring in 

selected nuclei, and the endpoint spectrum of tritium 

beta decay. Neutrino-less double beta decay is an 

extremely weak process that requires placement of the 

detector very deep underground. Tritium beta decay 

experiments require construction of very large and 

precise electron spectrometers.

Current Projects: The Super Kamiokande (SuperK) 

experiment is located in an underground mine in Japan 

and consists of a huge water tank to search for proton 

decay and neutrino interactions. The first evidence for 

a non-zero neutrino mass was obtained by SuperK in 

1998 and operations are continuing. 

(http://www-sk.icrr.u-tokyo.ac.jp/doc/sk/index.html)

K2K is a Long-baseline Neutrino Oscillation 

Experiment from the High Energy Accelerator 

Research Organization (KEK) accelerator laboratory in 

Japan to the SuperK detector. 

(http://neutrino.kek.jp/)

SNO is the Sudbury Neutrino Observatory, which 

searches for neutrino flavor oscillations due to their 

having mass. Initial results from SNO in combination 

with SuperK results led to the determination that 

neutrinos have mass and will require a revision of 

the Standard Model of Particle Physics. Subsequent 

measurements by SNO alone confirmed the Bahcall 

Standard Solar Model of fusion reactions in the Sun 

for the Sun's production of neutrinos and the results 

of the original solar neutrino experiment of Ray Davis 

Project Name Steward

Participating 

Agencies Scientific Approach Status

SuperK Japan DOE - High Energy 

Physics

Large volume Cherenkov Detector 

for proton decay, neutrino studies

Ongoing 

Project

K2K Japan DOE - High Energy 

Physics

Neutrino beam to SuperK detector 

to detect neutrino oscillations

Ongoing 

Project

SNO Canada

DOE - Nuclear 

Physics, High 

Energy Physics

Large volume Cherenkov Detector 

to study solar and astrophysical 

neutrinos

Ongoing 

Project

KamLAND Japan

DOE - High Energy 

Physics and Nuclear Physics

Large volume scintillation detector to look at antineutrinos from 

reactors

Ongoing 

Project

MiniBooNE DOE - High Energy 

Physics

NSF - Physics

DOE - Nuclear 

Physics, NNSA

Large detector that searches for 

neutrino oscillations using Fermilab accelerator

Ongoing 

Project

NUMI/MINOS DOE - High Energy 

Physics

NSF - Physics

DOE - NNSA

Study neutrino oscillations using 

neutrino beam from the Fermilab 

Main Injector

Under

Construction

BOREXino Italy NSF - Physics and 

Astronomy

Study solar neutrinos using a large 

scintillation detector

Under

Construction
33

and colleagues on solar neutrino oscillations. The 

2002 Nobel Prize in Physics was awarded to Davis and 

Koshiba for their pioneering work in this field.

(http://www.sno.phy.queensu.ca/)

The Kamioka Liquid scintillator Anti-Neutrino 

Detector (KamLAND) experiment in Japan measures 

the anti-neutrino flux from reactors in Japan and 

Korea to investigate neutrino oscillations. It also has 

sensitivity to detect low energy solar neutrinos. 

(http://kamland.lbl.gov/) 

MiniBooNE is a neutrino experiment at Fermilab 

that takes a beam of muon neutrinos from the booster 

accelerator and looks for electron neutrinos in the 

MiniBooNE detector. 

(http://www-boone.fnal.gov/)

The NUMI/MINOS project, under construction, will 

use a beam of protons from the Fermilab Main Injector 

to produce neutrinos aimed at an underground mine in 

Minnesota. There are two detectors, one at Fermilab 

and one in the mine, which will observe and measure 

neutrino oscillations. 

(http://www-numi.fnal.gov/)

BOREXino is a new solar neutrino experiment 

under construction designed to detect low-energy 

solar neutrinos, in real time, using 300 tons of liquid 

scintillator in an unsegmented detector. The detector 

is located in the Gran Sasso underground laboratory in 

Italy.

(http://pupgg.princeton.edu/~borexino/welcome.html)
34

Question 6. How Do Cosmic Accelerators Work and What Are They 

Accelerating?

“Physicists have detected an amazing variety of energetic phenomena in the universe, including beams of 

particles of unexpectedly high energy but of unknown origin. In laboratory accelerators, we can produce 

beams of energetic particles, but the energy of these cosmic beams far exceeds any energies produced on 

Earth.”

Scientific Significance: The observation of particles 

in the universe with unexpectedly high energy raises 

several basic questions. What are the particles? 

Where are their sources? How did they achieve such 

high energies—up to billions of times more energetic 

than those generated in the most powerful laboratory 

accelerators? These are likely atomic and subatomic 

particles moving essentially at light speed, each 

carrying the kinetic energy of a major league baseball 

pitch. Their existence might point to new physics.

Acceleration of particles to high energy is a 

characteristic feature of many energetic astrophysical 

sources, ranging from solar flares and interplanetary 

shocks to galactic supernova explosions, to distant 

active galaxies powered by accretion onto massive 

Black Holes, and to gamma ray bursters. Accelerated 

particles from space are called cosmic rays. It remains 

unproven just which structures contribute to such 

acceleration and whether the acceleration mechanisms 

actually work as hypothesized. Cosmic rays are 

Seen in this Hubble telescope image is a black-hole-powered jet of electrons and other sub-atomic particles traveling at nearly the speed 

of light. The monstrous black hole at the center of galaxy M87 has swallowed up matter equal to two billion times our Sun’s mass.
35

charged particles, and their paths are influenced by 

magnetic fields throughout the universe.

The signature of cosmic accelerators is that the 

accelerated electrons, protons, and heavier ions have 

a distribution of energies that extends far above the 

thermal distribution of particles in the source. It is the 

extreme energy that makes this population of naturally 

occurring particles of great interest, together with the 

fact that their energy density appears to be comparable 

to that of the thermal gas and magnetic fields in their 

sources. Primary cosmic ray electrons, protons, and 

nuclei can produce secondary photons (often in the 

form of a gamma ray) and neutrinos in or near the 

sources, which then propagate over large distances 

through the universe undeflected by the magnetic fields 

that obscure the origins of their charged progenitors. 

Photons are produced by electrons, protons, or nuclei, 

while neutrinos are produced only by the decays of 

protons and nuclei. The proportions of the various 

types of particles, secondary and primary, thus reflect 

the nature of their sources. A unified approach to 

the problem therefore requires observations of the 

gamma rays and neutrinos as well as the cosmic rays 

themselves.

Measurement Methods: There are many ways observe 

cosmic accelerations at work in the universe including 

measurements of high-energy cosmic rays, gamma 

rays, and neutrinos. They include ground-based and 

space-based detectors.

Observations of nature also need to be supplemented 

with laboratory studies of plasma environments and 

mechanism that are believed to be involved. This can 

be accomplished through several means. First, the 

collective injection and acceleration of particles can 

now be studied in university-center-scale facilities, and 

this requires coherent planning by the agencies that 

support this community. Second, clever use of ultraintense lasers will aid in the modification of particle 

distributions by means of relativistic collective plasma 

phenomena. Third, the effects of plasma interactions 

on the behavior of ultra-relativistic particles can now 

be studied using modern particle accelerators. In each 

case, theoretical and computational efforts will be 

needed to address the fundamental physics involved.

Current Projects: The Antarctic Muon and Neutrino 

Detector Array (AMANDA) is a unique telescope 

designed to detect energetic neutrinos from cosmic 

sources. The telescope consists of 19 strings of optical 

modules buried 1 to 1.5 miles beneath the ice surface of 

the geographic South Pole. Cherenkov light from fastmoving muons (cosmic rays) is converted to electrical 

signals by the photomultiplier tubes within each optical 

module. 

(http://amanda.uci.edu/)

IceCube is a one-cubic-kilometer international high 

energy neutrino observatory being built and installed 

in the clear deep ice below the South Pole Station. 

IceCube will open unexplored bands for astronomy, 

including the PeV (1015 eV) energy region, where 

the universe is opaque to high energy gamma rays 

originating from beyond the edge of our own galaxy, 

and where cosmic rays do not carry directional 

information because of their deflection by magnetic 

fields. 

(http://icecube.wisc.edu/)

The High Resolution Fly’s Eye (HiRes) is a twostation, air fluorescence observatory in Utah for 

measuring the energy spectrum, composition, and 

Schematic layout of the IceCube high energy neutrino observatory located at the South Pole Station (90 degrees south). A 

cubic kilometer of deep ice instrumented with 4800 optical modules (red circles) will detect Cherenkov light generated by the 

passage of muons and other charged particles produced when 

high energy neutrinos interact in or near the fiducial volume.
36

Artists concept of GLAST telescope which will map the high energy gamma ray sky. The major instrument is 

a collaboration between DOE and NASA with four international partners. Planned launch date is 2007.
37

processes such as those in Black Hole accretion disks. 

(http://www.lanl.gov/milagro/index.shtml)

The ground-based Pierre Auger observatory is 

under construction and now collecting data with an 

engineering array. This observatory will detect and 

study ultra high energy cosmic rays (UHECR) using a 

very large array of detectors in Argentina. 

(http://www.auger.org/)

The Alpha Magnetic Spectrometer (AMS) will study 

the properties and origin of cosmic particles and 

nuclei, including antimatter and Dark Matter in the 

unique environment of space. AMS is scheduled to be 

arrival direction anisotropy of ultra-high energy 

(>1017 eV) cosmic rays.

(http://hires.physics.utah.edu/)

The South Pole Air Shower Experiment (SPASE) 

is a large-area air shower array established at the 

geographic South Pole for the detection of cosmic rays 

with primary energies above 50 TeV. 

(http://www.bartol.udel.edu/spase/)

MILAGRO is the Multiple Institution Los Alamos 

Gamma Ray Observatory. MILAGRO looks at TeV 

energy photons from active galactic nuclei and gamma 

ray bursts, which gives insight into high energy 

Project Name Steward

Participating 

Agencies Scientific Approach Status

AMANDA NSF - Office of 

Polar Programs

DOE - High Energy 

Physics

NSF - Physics

Major International 

Participation

Under-ice telescope to detect 

energetic neutrinos

Ongoing 

Project

HiRes NSF - Physics

Ground-based observatory to 

measure the composition and 

energy of high energy cosmic 

rays

Ongoing 

Project

SPASE NSF - Office of 

Polar Programs

Large area array to measure very 

energetic particles (> 50 TeV)

Ongoing 

Project

MILAGRO NSF - Physics DOE - High Energy 

Physics, NNSA

Ground-based observatory to 

detect high energy gamma rays

Ongoing 

Project

Pierre Auger International

DOE - High Energy 

Physics

NSF - Physics

NSF - Astronomy

Large area array to detect high 

energy cosmic rays

Under

Construction

GLAST NASA - Office of 

Space Science

DOE - High Energy 

Physics

International

Space-based mission to measure 

high energy gamma rays

Under

Construction

AMS DOE - High Energy 

Physics

NASA - Office 

of Biological and 

Physical Research

Major international 

participation

Magnetic spectrometer on the 

International Space Station to 

search for Dark Matter and antimatter

Under

Construction

ICECUBE NSF - Office of 

Polar Programs

NSF - Physics

International 

participation

Under-ice observatory to 

measure astrophysical neutrinos

Under

Construction

VERITAS NSF - Astronomy

DOE - High Energy 

Physics

NSF - Physics

Smithsonian

Ground-based array to detect 

gamma rays in the range 40 GeV 

to 50 TeV

Under 

Construction
38

deployed for a three-year mission on the International 

Space Station in 2007.

(http://ams.cern.ch/AMS/ams_homepage.html)

GLAST is the Gamma ray Large Area Space Telescope, 

a particle detector in space planned for a 2007 launch. 

GLAST will map the high energy gamma ray sky 

to study the mechanisms of particle acceleration in 

extreme astrophysical environments. Radiation of 

such magnitude can only be generated under extreme 

conditions, therefore GLAST will focus on studying the 

most energetic objects and phenomena in the universe 

such as how Black Holes, notorious for pulling matter 

in, can accelerate jets of gas outward at fantastic 

speeds. It will also search for Dark Matter candidate 

particles.

(http://glast.gsfc.nasa.gov/)

The Very Energetic Radiation Imaging Telescope Array 

System (VERITAS) is a ground-based array which has 

recently started construction. The array of four 12m 

imaging telescopes will detect atmospheric Cherenkov 

radiation in the range 50 GeV to 50 TeV.

(http://veritas.sao.arizona.edu/)
39

Question 7. Are Protons Unstable?

“The matter of which we are made is the tiny residue of the annihilation of matter and antimatter that 

emerged from the earliest universe in not-quite-equal amounts. The existence of this tiny imbalance may be 

tied to a hypothesized instability of protons, the simplest form of matter, and to a slight preference for the 

formation of matter over antimatter built into the laws of physics.”

Scientific Significance: One of the simplest and 

most profound questions in science is whether or not 

the proton, the building block of atoms, has a finite 

lifetime and will eventually decay. Unified theories 

of elementary particles and fields, which have had 

great success explaining the behavior of subatomic 

and nuclear particles, predict that the proton cannot 

be stable. This is one of the most generic and most 

testable predictions of grand unification: the proton 

must ultimately decay. The implication is that even 

hydrogen, the majority constituent of the universe, has 

a finite lifetime. In addition, observations of proton 

decay would provide us with a unique window to view 

physics at truly short distances—the proton is less than 

10-30 cm in size. In order to probe this time scale in 

an accelerator experiment, energies greater than 1025

eV would be required; this is one trillion times greater 

than planned terrestrial accelerators and ten thousand 

times greater than the highest energy cosmic rays. The 

physics of proton decay is also related to the excess of 

matter over antimatter in the universe. Detection of 

proton decay will provide a missing link in our theories 

of grand unification.

Measurement Methods: Theories predict that the 

average lifetime of protons is greater than 1035 years. 

The universe is only 13.7 billion (1.37 × 1010) years 

old, so most protons will not decay until the universe 

The inside of the SuperK tank before filling.
40

Project Name Steward

Participating 

Agencies Scientific Approach Status

SuperK Japan DOE - High Energy 

Physics

Large volume Cherenkov 

Detector for proton decay, 

neutrino studies

Ongoing 

Project

is ten million billion billion times older than it is 

now. Since the event being sought is so rare, it is 

necessary to observe a large number of protons with 

minimum background noise. This requires observing 

a megaton of water in an underground laboratory 

with an ultra-clean detector. Such experiments can 

also accommodate an extensive neutrino physics 

program that could study neutrinos from the next 

nearby supernova, terrestrial accelerators, and 

other cosmic sources. The lack of observed decays 

among the protons observed in experiments to date 

sets the average proton lifetime at greater than 1032

to 1033 years. The next generation of proton decay 

experiments should provide the first detected proton 

decay if theories are correct.

Current Projects: The detection of proton decay is 

being pursued in the large volume detectors used for 

neutrino studies. For example, the Super Kamiokande 

(SuperK) experiment located in an underground mine 

in Japan consists of a huge water tank to search for 

proton decay and neutrino interactions. The first 

evidence for a non-zero neutrino mass was obtained by 

SuperK in 1998 and operations are continuing.

(http://www-sk.icrr.u-tokyo.ac.jp/doc/sk/index.html)
41

Question 8. What Are the New States of Matter 

at Exceedingly High Density and Temperature?

“The theory of how protons and neutrons form the atomic nuclei of the chemical elements is well 

developed. At higher densities, neutrons and protons may “dissolve” into an undifferentiated “soup” of 

quarks and gluons, which can be probed in heavy-ion accelerators. Still higher densities and temperature 

occur and can be probed in neutron stars and the early universe."

Scientific Significance: One of the most fruitful 

strategies to advance the frontiers of science is to 

push observation into unexplored territory. One 

such territory is the realm of extreme conditions of 

temperature and pressure in macroscopic systems. 

Here we are speaking of extreme plasma conditions, a 

topic that lies solidly at the intersection of physics and 

astronomy. Examples in astronomy are found in the 

study of compact objects such as neutron stars or Black 

Holes and their accretion disk systems.

Matter at high density has been studied for several 

decades using accelerators to attempt to create the 

elusive matter that is thought to have existed during 

the early universe: the quark-gluon plasma. At normal 

temperatures and densities, nuclear matter contains 

individual protons and neutrons that are made up of 

three quarks, “glued” or bound together by gluons. At 

extremely high temperatures, however, such as those 

that existed in the early universe immediately after the 

Big Bang, quarks and gluons are liberated and form a 

quark-gluon plasma. This plasma may also exist today 

in the cores of neutron stars, which capture matter at 

extreme densities.

Yet another approach to this basic question about 

exotic states of matter is represented by the rapidly 

growing field of high-energy-density (HED) physics. 

Its roots are in such fields as fusion energy, particle and 

nuclear physics, laser science, and astrophysics. But 

the potential intellectual connections and synergies 

have not been exploited, nor has a robust academic 

community developed to infuse new ideas and talent 

into the many vital applications and intellectual 

frontiers intertwined with the study of high-energydensity physics. Also included in the scope of this 

science question are related questions of turbulence, 

novel states of matter, and other manifestations 

of emergent behavior in complex systems. Taken 

together, studies of such complex phenomena in 

the laboratory and by theoretical and computational 

means will provide the essential intellectual ferment 

to understand the astrophysical phenomena outlined 

above.

Measurement Methods: Several approaches to highenergy-density physics have sprung up in various 

programs and communities. The approaches include 

astrophysical observations, accelerator physics, laser 

physics, magnetically confined plasmas, z-pinch, high 

Relativistic Heavy Ion Collider (RHIC) at Brookhaven National 

Laboratory. The machine itself is enclosed in a tunnel, 12 feet 

under the ground. Inside two tubes, ion bunches race around 

RHIC’s 2.4-mile ring in opposite directions.

Computer simulation of the collision of two gold ions at an 

energy of 200 billion electron volts (200 GeV).
42

energy density laser-drivers, numerical simulation, and 

advanced diagnostics, often in combination with one 

another.

For decades, accelerators have been used to probe the 

physics of the universe, unveiling bits of knowledge 

about the behavior of matter that existed in the early 

universe that bring us closer to understanding how the 

universe began. Large heavy-ion accelerators are used 

to collide heavy nuclei together at ultra-relativistic 

energies to create the hot, dense matter. Initial results 

have provided tantalizing indications that a quark-gluon 

plasma with fascinating properties can be produced in 

these collisions. This direction of work will shed light 

on the processes that governed the early universe.

The emerging field of high-energy-density plasma 

physics also has much to offer to this question. Such 

plasmas will increasingly prove able to produce 

Project Name Steward

Participating 

Agencies Scientific Approach Status

RHIC DOE - Nuclear 

Physics

NSF - Physics

DOE - NNSA

International

Heavy ion collisions creates primordial matter in the laboratoryOngoing 

Project

RXTE NASA - Office of 

Space Science

Space-based mission to observe 

extreme states of matter through 

X-ray emission

Ongoing 

Project

extreme conditions that are directly relevant to 

astrophysical phenomena. For example, new ultraintense lasers and next-generation laser-driven plasma 

devices can be used to generate plasma conditions 

with ultrastrong magnetic fields relevant to neutron 

star atmospheres. Furthermore, it is believed that 

compact objects also at times involve radiationdominated plasmas, a topic that will be addressable 

with laboratory-based facilities in the near future. The 

National Nuclear Security Administration within the 

Department of Energy is currently constructing the 

National Ignition Facility (NIF) for the purpose of 

achieving inertial confinement fusion (ICF) ignition 

in the laboratory. This facility, and the current ICF 

facilities; Z at Sandia National Laboratories and 

Omega at the University of Rochester, are able to 

compress and heat matter to conditions relevant to 

astrophysical environments. Creating these conditions 

in the laboratory in a controlled manner, contributes 

to the interpretation and understanding of a variety of 

high energy density astrophysical phenomena such as 

supernovae, stellar atmospheres, neutron stars, etc.

Current Projects: Beams of atomic nuclei at the 

Relativistic Heavy Ion Collider (RHIC) at Brookhaven 

National Laboratory are collided to recreate brief, tiny 

samples of quark-gluon plasma, the matter that existed 

in the early stages of the universe. 

(http://www.bnl.gov/rhic/)

RXTE is the Rossi X-ray Timing Explorer, a space 

mission that studies compact objects such as white 

dwarfs and neutron stars through the temporal and 

spectral variability of their X-ray emission. Light 

curves of neutron stars obtained with RXTE are being 

used to constrain the equation of state for nuclear 

matter in degenerate stars. The mass to radius ratio 

of neutron stars, for example, may determine if such 

environments are hot and dense enough to possess the 

quark-gluon plasma. 

NASA's Rossi X-ray Timing Explorer, which was launched (http://rxte.gsfc.nasa.gov/)

December 30, 1995.
43

Question 9. Are There Additional Space-Time Dimensions?

“In trying to extend Einstein’s theory and to understand the quantum nature of gravity, particle physicists 

have posited the existence of space-time dimensions beyond those that we know. Their existence could have 

implications for the birth and evolution of the universe, could affect the interactions of the fundamental 

particles, and could alter the force of gravity at short distances."

Scientific Significance: There are only a handful 

of examples of new, scientific ideas that have the 

power to change our basic view of the universe. The 

roundness of the Earth was a big paradigm change 

that emerged. Copernicus and others recognized the 

heliocentric nature of the solar system. The expansion 

of the universe and its origin in a Big Bang were 

revolutionary scientific ideas. Another scientific 

speculation of that magnitude is that the universe 

may exist in more than the three spatial and one time 

dimensions that we are familiar with.

This idea is expressed in so-called string theory, which 

suggests that the universe is expressed in up to eleven 

dimensions, all but four of which are tightly rolled 

up so that they are not evident to our senses. This 

sounds bizarre, but it has the potential to explain longstanding scientific puzzles, such as the weakness of the 

When magnifying matter, the fundamental constitutents apear to be point-like. But if we were able to magnify even more, what would 

they look like? String theory presents a possibility to unify particle physics with gravity provided that the particles are string-like at a 

lengthscale of 10-33 m.

–Martin Lübcke, Uppsala University
44

orbit around Mars also has the potential to provide the 

required precision. Such deviations, the prediction 

of string theory, would signal a deviation from the 

predictions of general relativity at the largest scales.

Another way that evidence for extra dimensions may be 

found is by looking for their signature in high energy 

particle collisions produced by particle accelerators. 

If the energy of particle collisions can be made high 

enough, the production of a “graviton,” the force carrier 

of gravity, could provide signatures of the existence 

of extra dimensions. The signature would be missing 

energy in a collision. 

Finally, the theory that underlies many of the 

predictions of extra space-time dimension is string 

theory. Further theoretical developments in this area 

are vital to the development of dedicated and wellfocused experimental efforts in the search for extra 

dimensions.

Current Projects: No dedicated current projects.

The search for extra dimensions is an important goal 

of experiments using the highest energy particle 

accelerators, such as the Fermilab TeVatron and 

the Large Hadron Collider (LHC), which is under 

construction. Accelerator searches for extra dimensions 

are not done with dedicated experiments, though, but 

rather can be done in conjunction with the analysis of 

data being collected.

gravitational force relative to the other forces. It is also 

possible that cosmic acceleration is not caused by Dark 

Energy but is rather due to a breakdown of General 

Relativity on the larger scales. A new law of gravity 

may emerge from string theory. These issues are grand 

challenges at the frontiers of physics; and they underlie 

some of the deep mysteries of the cosmos.

Measurement Methods: The existence of extra 

dimensions or degrees of freedom are postulated to 

have several possible experimental signatures. One 

of the key elements to these tests for extra dimensions 

is their coupling to gravitational phenomena. The 

energy at which this coupling occurs is not well defined 

theoretically, however.

Several experimental approaches that could signal 

extra dimensions are lunar laser ranging experiments 

and “equivalence principle” experiments. Equivalence 

principle experiments are precision laboratory-scale 

experiments that search for deviations from predictions 

from a 1/r2 law dependence of the gravitational 

attraction between two objects. String theory models 

predict a deviation from the 1/r2 law, but the level of 

deviations has not been worked out.

Lunar Laser “ranging,” or distance measurements, with 

a factor of ten improved precision, also look for small 

deviations in the gravitational force between objects, 

but on a much larger scale. Ranging to spacecraft in 

Schematic Drawing of the Eöt-Wash Short-range Experiment. The University of Washington Eöt-Wash group recently 

measured the strength of gravity at a distance of less than 0.2 

millimeter and found no deviation in the gravitational pull from 

that predicted by Newton’s inverse-square law. 

Artist’s conception of a graviton being produced in a high energy 

proton antiproton collision and moving off into an extra dimension.
45

Question 10. How Were the Elements from Iron to Uranium Made?

“Scientists’ understanding of the production of elements up to iron in stars and supernovae is fairly 

complete. The precise origin of the heavier elements from iron to uranium remains a mystery."

Scientific Significance: While we have a relatively 

good understanding of the origin of elements lighter 

than iron, important details in the production of 

elements from iron to uranium remain a puzzle. Picture 

the periodic table. The existence of every element with 

an atomic number higher than iron—such as silver and 

gold—presents a mystery.

A sequence of rapid neutron captures by nuclei, 

known as the r-process (where r is for rapid), is 

Researchers using an Oak Ridge National Laboratory supercomputer have found that the organized flow beneath the outgoing shock 

wave in a supernova explosion persists in three dimensions. This fluid flow develops beneath the shock and, when coupled to nuclear 

and neutrino ineractions, is believed to lead to the explosion. The enormous energies that this generates creates an environment where 

elements of life are synthesized.
46

clearly involved, as may be seen from the observed 

abundances of the various elements. Supernova 

explosions, neutron-star mergers, or gamma ray 

bursters are possible locales for this process. 

Tremendous forces must fuse lighter elements into 

heavier ones. But our incomplete understanding of 

these events leaves the question open. 

Measurement Methods: There are four methods to 

determine the origin of heavy elements: acceleratorbased studies of rare isotopes, studies of high-energydensity plasmas, astrophysical observations of X-rays 

and gamma rays, and theory and simulations.

The creation of exotic nuclei with accelerators enables 

the study of nuclei at the limits of stability. Almost 

all the relevant r-process nuclei could be accessible 

for study in a suitably designed two-stage acceleration 

facility that produces isotopes and re-accelerates them. 

Such an accelerator is being designed and would 

provide the capability for producing the beams of 

short-lived nuclei needed for an understanding of the 

synthesis of nuclei observed in the universe.

Laboratory studies of high-energy-density plasmas 

come into play in providing new knowledge concerning 

the complex plasma physics in supernovae, in 

providing input data for simulations, and for validating 

simulations. The dynamics of plasma hydrodynamic 

turbulence in particular is a substantial intellectual 

challenge. It has been demonstrated that experiments 

can be done in the laboratory that can simulate the 

strong-shock-driven turbulent hydrodynamics of 

a supernova explosion. It will also be possible to 

This image of the Cas A supernova remnant shows remarkable structure in the debris of a gigantic stellar explosion, as well as an enigmatic source in the center, which could be a rapidly spinning neutron star or black hole. The low, medium, and higher X-ray energies of 

the Chandra X-ray Observatory data are shown as red, green, and blue, respectively.
47

Current Projects: Low-energy nuclear physics 

facilities such as the Holifield Radioactive Ion 

Beam Facility (HRIBF) (http://www.phy.ornl.gov/

hribf/hribf.html/), the Lawrence Berkeley National 

Laboratory LBNL 88” Cyclotron (http://www.lbl.

gov/nsd/user88/index.html) and the Argonne Tandem 

Linac Accelerator System (ATLAS) (http://www.phy.

anl.gov/atlas/index.html) study interactions in nuclear 

matter like those that occur in neutron stars and those 

that create the nuclei of most atomic elements inside 

stars and supernovae and investigate new regions of 

nuclear structure.

The National Superconducting Cyclotron Laboratory 

(NSCL) is a rare isotope research facility at Michigan 

State University, conducting research in fundamental 

nuclear science, nuclear astrophysics, and accelerator 

physics. NSCL operates two coupled superconducting 

cyclotrons: the K500, the first cyclotron to use 

superconducting magnets, and the K1200, the highest 

energy continuous nuclear beam accelerator in the 

world. 

(http://www.nscl.msu.edu/) 

In addition to these focused projects, some X-ray 

and gamma ray space observatories have sufficient 

sensitivity and spectroscopic capability to be capable 

of observing the spectral signatures of newly formed 

elements soon after supernova explosions and other 

nucleosynthesis events. These include the Chandra 

X-ray Observatory and the European Space Agency’s 

XMM-Newton and INTEGRAL observatories.

replicate supernova remnant dynamics by scaled 

radiative shock dynamics experiments.

For the outputs, sensitive high energy X-ray and 

gamma ray space experiments will allow us to observe 

the decays of newly formed elements soon after 

supernova explosions and other major astrophysical 

events. Comparison of these observations with the 

outputs of simulations can constrain the theoretical 

models for explosions. Better measurements of 

abundances of certain heavy elements in cosmic rays 

may also provide useful constraints.

Simulating the processes involved in the initiation, 

evolution, and aftermath of supernovae is central 

to understanding the existence and distribution of 

elements in the cosmos. This includes computing the 

complex chain of nuclear reactions, the dynamics of 

the multistage explosion process that take place during 

a supernova, and the complex interstellar dynamics 

that govern the injection of supernova debris into 

interstellar space. Taken together, the interdependent 

set of approaches outlined above can provide an 

understanding of the processes by which the elements 

of the periodic table were generated and dispersed in 

the cosmos.

Project Name Steward

Participating 

Agencies Scientific Approach Status

HRIBF, LBNL 

88-inch Cyclotron, 

ATLAS

DOE - Nuclear 

Physics DOE - NNSA Accelerator facilities to study interactions in nuclear matter

Ongoing 

Project

NSCL NSF - Physics DOE - Nuclear 

Physics, NNSA Rare isotope research facility Ongoing Project
48

Question 11. Is a New Theory of Matter and Light Needed 

at the Highest Energies?

“Matter and radiation in the laboratory appear to be extraordinarily well described by the laws of quantum 

mechanics, electromagnetism and their unification as quantum electrodynamics. The universe presents us 

with places and objects, such as neutron stars and the sources of gamma ray bursts, where the energies are 

far more extreme than anything we can reproduce on Earth in order to test these basic theories.”

Scientific significance: As we have seen in many of 

the scientific questions discussed above, processes 

occurring in the cosmos provide a unique opportunity 

to study physical conditions that cannot be realized in 

laboratories on earth. Yet another example involves 

the theory of matter and light at extremely high 

electromagnetic fields.

Quantum electrodynamics (QED) is a highly 

successful, quantitative quantum theory of the 

electromagnetic interactions of photons and matter. 

It makes predictions that have been tested with great 

precision in regimes accessible to laboratory study. 

In particular, it has been tested in static magnetic 

fields as large as roughly 105

 gauss (G), a hundred 

thousand times stronger than the earth’s magnetic 

field. However, ever since the discovery of pulsars, 

it has been known that fields as large as 1012 G, seven 

orders-of-magnitude larger, are commonly found on the 

surfaces of neutron stars.

More recently it has been concluded that a subset of 

neutron stars, called “magnetars,” have magnetic field 

strengths in the range 1014 to 1015 G, well above the 

QED “critical” field, where the kinetic energy of an 

electron spiraling in the magnetic field exceeds its rest 

mass energy. QED should still hold above this critical 

field, but the physics is quite different from what is 

normally considered. For example, when an X-ray 

propagates through vacuum endowed with a strong 

magnetic field, QED predicts that electron-positron 

pairs will be created in such a way that the emergent Xray radiation will become polarized. It may therefore 

be possible to observe QED at work in magnetars by 

observing X-ray polarization and mapping out the 

neutron star magnetic field.

Measurement Methods: To carry out such 

observations will require sensitive X-ray instruments 

capable of measuring polarization, which are being 

developed for X-ray synchrotron facilities and for 

space-based observatories.

Current Projects: None.

Concept image of what a magnetar might look like. The thin 

blue lines are renderings of the superstrong magnetic field lines 

of this kind of star.
49

Appendix I. Agency Research Practices and Approaches

The three primary agencies supporting research at 

the intersection of physics and astronomy—DOE, 

NASA, and NSF—each have different cultures 

and characteristics that derive from their missions. 

These differences among the agencies in terms of 

organizational structures, program management, and 

planning processes impact the interactions among the 

agencies and the ease with which they will implement 

the various recommendations contained within this 

report.

Organizational Structures

Department of Energy, Office of Science: The Office 

of Science is the third largest business line within the 

Department of Energy, a cabinet-level agency. The 

Office of Science sponsors fundamental research 

into the nature of matter and energy as well as basic 

research that furthers the security, environmental cleanup, and energy technology missions of the Department 

of Energy. To carry out its basic research mission, the 

Office of Science designs, constructs, and operates 

an extensive suite of large scientific user facilities for 

the benefit of the nation’s public and private research 

enterprise. These facilities include particle accelerators 

and colliders, X-ray synchrotron light sources, neutron 

sources, electron microscopes, genome sequencing 

facilities, atmospheric measurement facilities, and 

supercomputers. Large, long-term multidisciplinary 

research teams are the primary vehicle through which 

the Office of Science achieves its scientific objectives. 

The Office of Science’s approach to conducting 

research is strongly influenced by the origins of 

DOE’s precursor agencies, the Atomic Energy 

Commission and the Energy Research & Development 

Administration, which date to the Manhattan Project. 

DOE teams are most often centered at one of the 

Department’s National Laboratories and almost always 

include university-based researchers. International 

collaborations on multi-year experiments are common.

Two of the Office’s six major programs—High Energy 

Physics and Nuclear Physics—sponsor the majority of 

the DOE research within the scope of the Physics of the 

Universe program.

The mission of the High Energy Physics (HEP) 

program is to explore the fundamental nature of matter, 

energy, space, and time. The core of the program 

centers on investigations of elementary particles and 

the interactions between them, thereby underpinning 

and advancing DOE missions and objectives through 

the development of key cutting-edge technologies 

and trained manpower. The major tools used are high 

energy particle accelerators.

The DOE HEP program provides about 90 percent of 

the federal support for high energy physics research in 

the United States, with NSF providing most of the rest. 

The program involves over 2,450 researchers at over 

100 universities in 36 states, Washington, D.C., and 

Puerto Rico, as well as eight laboratories located in five 

states. The program supports two major accelerator 

user facilities in the United States: the TeVatron 

proton-antiproton collider at Fermilab in Illinois, and 

the B-factory electron-positron collider at SLAC in 

California.

The HEP program sponsors proposal-driven university 

research as an integral part of the HEP program. 

Reviews of the progress and plans of the individual 

university groups is obtained through community mailin peer review, peer-review panels, and through site 

visits by program managers in the HEP program office. 

Specialized programs using competitive peer review 

include an Outstanding Junior Investigators Award 

for new tenure-track faculty members, the Advanced 

Detector Research Award, and the Linear Collider 

Detector Research and Development Award.

The DOE Nuclear Physics (NP) program aims to 

understand the composition, structure, and properties 

of atomic nuclei, the processes of nuclear astrophysics 

and the nature of the cosmos. Today, its reach extends 

from the quarks and gluons that form the substructure 

of the once-elementary protons and neutrons, to the 

most dramatic of cosmic events-supernovae.

The DOE NP program provides about 90 percent of 

the federal support for fundamental nuclear physics 

research in the nation. The program involves over 

1,900 researchers and students at over 100 U.S. 

academic, Federal, and private sector institutions. The 

program funds research activities at over 85 academic 

institutions located in 35 states and at seven DOE 

Laboratories in six states.
50

In FY 2003, the DOE NP program supported five 

accelerator facilities at national user laboratories in 

the United States: RHIC, CEBAF, HRIBF, the 88-inch 

Cyclotron, and ATLAS. University researchers play 

a critical role in the nation’s nuclear physics research 

effort and in the training of graduate students; the DOE 

NP program supports approximately two-thirds of the 

nation’s university researchers and graduate students 

doing fundamental nuclear physics research. The 

grants program is proposal-driven and funds the best 

and brightest of those ideas submitted in response to 

grant solicitation notices. The program supports five 

university-based accelerator facilities, each providing 

unique capabilities and excellent hands-on training for 

the next generation of scientists.

The Office of Science’s Fusion Energy Sciences 

(FES) program supports advances in plasma and 

fusion science to develop the knowledge base needed 

for an economically and environmentally attractive 

fusion energy source. FES pursues this goal through 

an integrated program of research based in U.S. 

universities, industry, and national laboratories, 

augmented by a broad program of international 

collaboration. As part of this effort, a growing effort in 

high-energy-density physics research is pursued. This 

is primarily as an outgrowth of research on Inertial 

Fusion Energy which relies on high energy beams or 

lasers as possible compressive drivers. FES has also 

provided the fundamental university training for the 

majority of the scientists engaged in plasma-based high 

energy density physics research.

Department of Energy, National Nuclear Security 

Administration: The NNSA’s Inertial Confinement 

Fusion Ignition and High Yield program supports 

research at the intersection of physics and astronomy 

as a result of their primary interest in exploiting 

high-energy-density physics for nuclear weapons 

research. This program supports research using 

inertially-confined plasmas that contribute to the 

Physics of the Universe program in unique ways. 

Many of the measurements that may be made at these 

unique experimental facilities cannot be obtained in 

any other way and are crucial for the interpretation 

of observational data collected by DOE, NSF, and 

NASA. The NNSA recognizes the capability of its ICF 

facilities to address a number of interesting science 

questions outside of its mission, and therefore as a 

policy, NNSA provides a certain fraction, up to 15%, of 

the experimental time available on these facilities for 

users outside of the NNSA laboratories.

National Aeronautics and Space Administration:

The Office of Space Science (OSS) is the largest 

research enterprise within NASA, an independent 

Executive Branch agency. The OSS develops and 

mounts space missions to explore the universe and 

search for life. These space missions are the primary 

vehicle through which the Office of Space Science 

achieves its scientific and educational objectives. 

NASA organizes its space science activities around 

“science themes,” where long-term science goals 

are used to drive a series of missions. The Structure 

and Evolution of the Universe (SEU) theme overlaps 

the goals of the Connecting Quarks with the Cosmos

report. The Beyond Einstein Initiative, part of the 

President's FY2004 budget proposal, looks to address 

key questions relevant to this report, in particular: What 

powered the Big Bang? What happens at the edge of a 

Black Hole? What is Dark Energy?

NASA operates nine field centers and one 

federally-funded research and development center 

(Jet Propulsion Laboratory), which manage the 

implementation of most missions and support their 

operation. The Goddard Space Flight Center and 

Jet Propulsion Laboratory have responsibility to 

manage the implementation of OSS missions. The 

agency uses a structured and transparent project 

management process that employs full-time project 

managers, regular milestone reviews, and budgeting 

of contingency reserves. In addition NASA provides 

competitively selected grants to enable research based 

on the data generated by the missions and to develop 

the technology necessary to undertake future missions. 

The supporting research and technology development is 

carried out both in NASA centers and by investigators 

in universities and other laboratories.

Mission planning is comprehensive and encompasses 

technology development, conceptual design, instrument 

and spacecraft development, integration and test, 

launch, in-orbit mission operations, data collection and 

distribution, and research and data analysis. NASA 

supports a number of national data centers to archive 

and distribute the publicly accessible data generated by 

missions. The Explorer program provides a number of 

smaller missions that address the Connecting Quarks 

with the Cosmos science theme (e.g., WMAP). These 

are competitively selected small- and medium-sized 

scientist-led missions that are selected via an open 

competitive selection process. The largest missions are 

selected via the Agency’s strategic planning process, 

using science priorities set by the National Academy 
51

of Sciences decadal survey of Astronomy and 

Astrophysics. For these large facilities, instruments 

and science teams are selected via a competitive 

process.

National Science Foundation: The National Science 

Foundation is an independent Executive Branch agency 

that funds research and education in science and 

engineering. It does this through grants, contracts, and 

cooperative agreements to more than 2,000 colleges, 

universities, and other research and/or education 

institutions in all parts of the United States. The 

Foundation accounts for about 20 percent of federal 

support to academic institutions for basic research. It 

receives policy guidance from the National Science 

Board.

Each year, NSF receives approximately 40,000 new or 

renewal support proposals for research, graduate, and 

postdoctoral fellowships, and math/science/engineering 

education projects; it makes approximately 10,000 new 

awards. These typically go to universities, colleges, 

academic consortia, nonprofit institutions, and small 

businesses.

Management of NSF's research and education 

activities is divided among National Research Centers, 

major facilities in physics and astronomy, certain 

oceanographic vessels, and Antarctic research stations.

The management of the program is divided into seven 

directorates and several cross-cutting divisions and 

offices. The grants program at NSF is administered 

by individual discipline scientists and it funds 

the best ideas generated by the university-based 

research community, as judged by competitive 

peer review. Research grants are funded separately 

and independently from facility construction and 

operations. Project development and operations are 

conducted by outside entities—usually academic 

consortia or individual universities. The typical user 

who has been awarded observing time on a telescope 

through a competitive peer review process may also 

apply to NSF for a grant to carry out the research. 

The Foundation’s approach to conducting research is 

strongly influenced by the ideas espoused by Vannevar 

Bush.

The Mathematical and Physical Sciences (MPS) 

Directorate is the largest directorate within the 

Foundation. Two of MPS’s divisions—Astronomical 

Sciences and Physics—sponsor the majority of NSF 

research within the scope of the Physics of the Universe 

program. The Astronomical Sciences Division in 

the Mathematical and Physical Sciences Directorate 

has primary federal responsibility for ground-based 

astronomy and astrophysics research, including optical/

infrared, solar, and radio astronomy. NSF also supports 

ground-based planetary astronomy. The Physics 

Division is also a significant source of support for 

astrophysics research, including particle and nuclear 

astrophysics, gravitational physics, and theory. It is 

important to note that significant sources of research 

support for astronomy and astrophysics research 

are spread broadly across NSF. The Office of Polar 

Programs supports several astrophysical experiments in 

Antarctica. Solar research at NSF is supported by both 

the Astronomical Sciences Division and the Division of 

Atmospheric Sciences in the Geosciences Directorate. 

Program Management

Department of Energy: Within the Department 

of Energy, well-specified program and project 

management strategies are implemented for the 

acquisition of capital assets. Extensive independent 

reviews of the Technical, Cost, Schedule, and 

Management aspects of a project are held at each phase 

of the construction. In addition, there are reviews at 

several key points by an external independent review 

team. The planning and construction process of 

projects normally has four phases. Pre-conceptual 

phase activities take place before a project is formally 

defined and include identifying ideas, making 

preliminary evaluations of their feasibility, and 

documenting the need for the project. Costs in the 

pre-conceptual phase do not accrue to the total project 

cost. In the conceptual phase, technical and project 

requirements are defined and estimated resources 

are identified; conceptual design may not commence 

until a successful Mission Need Independent Project 

Review.

In the conceptual phase of the project, a conceptual 

design report and the project execution plan are 

prepared, both of which are critical in setting the 

preliminary scope, cost, and schedule baselines. Costs 

for the conceptual phase of the project are included 

in the total project cost. The execution phase begins 

after a successful review of the conceptual design and 

includes design and construction of the project and the 

transition to start-up and acceptance. Baseline scope, 

costs, and schedules are firmly established in a review 

process after a preliminary engineering phase and prior 
52

to the construction start. A closeout decision may be 

made at any time during the life of a project.

Generally by the time of the closeout phase, the project 

has been completed and turned over for operations. 

Closeout can also be the termination of an incomplete 

project or the retirement of a facility at the end of 

its life cycle. The progress in a project is tracked 

through monthly reports, quarterly reviews, and annual 

independent reviews. During the operations phase of 

an experiment, the progress and plans are reviewed by 

the appropriate advisory panels as well as through the 

yearly laboratory reviews.

National Aeronautics and Space Administration:

Within NASA, missions or projects are significant 

activities that have defined goals, objectives, 

requirements, life-cycle costs, a beginning, and an end. 

A NASA mission includes Formulation, Approval, 

Implementation, and Evaluation, and is divided into 

phases. Formulation consists of the concept study 

(Phase A) and the definition/preliminary design (Phase 

B). Approval is the process for transitioning from 

formulation into implementation, which can include a 

non-advocate review, a confirmation review with the 

appropriate Enterprise Associate Administrator, and the 

approval of a program commitment agreement (PCA) 

by the Agency Program Management Council and the 

Administrator. Implementation consists of detailed 

design and development (Phase C), integration, test, 

and launch operations extending through in-orbit 

checkout (Phase D), and mission operations and data 

analysis including analysis, publication, and public 

release of data (Phase E). The Evaluation process is 

not a separate phase but is the ongoing independent 

review and assessment of the project’s status during 

both Formulation and Implementation.

The PCA sets the requirements for the mission as 

well as the cost and schedule commitments. Costs 

considered are life-cycle costs through prime mission. 

To the maximum extent practical, competitive 

solicitations are used to select participants in a mission 

including the science team and the industry team. A 

mission may be terminated at any time for failure 

to meet the commitments in the PCA. Following 

the completion of the prime mission, and resources 

permitting, an extended mission may be approved 

through the Senior Review, a competitive peer review.

National Science Foundation: Planning and 

construction of major facilities by NSF are governed 

by the Foundation-wide “Facilities Management and 

Oversight Guide.” The Major Research Equipment 

and Facilities Construction (MREFC) account is an 

agency-wide capital asset account. It provides funding 

for the establishment of major science and engineering 

infrastructure, with costs ranging from several tens 

to hundreds of millions of dollars. LIGO and its 

proposed upgrade, as well as the proposed LSST and 

underground laboratory activities, are subject to this 

process.

To be eligible for consideration for MREFC funding, 

projects must: represent an exceptional opportunity 

that enables research and education essential to the 

nation’s science and engineering enterprise, with a 

broad base of support in the relevant community or 

communities; ensure that the awardee provides a 

strong project management structure that is appropriate 

to the size and complexity of the project, including 

clear lines of communication and authority; and have 

undergone a thorough external review, including highlevel assessment of scientific and engineering research 

merit, broader impacts (e.g., integrating research 

and education), technical and engineering feasibility, 

opportunities for interagency and/or international 

collaboration and cost sharing, and relevant 

management issues and accuracy of cost, schedule, and 

contingency estimates, including projected operating 

costs.

Planning proceeds through a defined, staged process 

that provides early visibility of projects to NSF 

management and to the National Science Board while 

the project matures from concepts developed within the 

scientific community to a funded activity. Appropriate 

management structures, oversight mechanisms, and 

lifecycle costing are instituted early in the planning and 

become part of the overall decision package presented 

to the National Science Board.

Projects at a smaller scale and elements of R&D 

prepatory to construction phases for large facilities 

may be handled directly through the programs of 

the divisions and offices for which they are most 

appropriate. Examples of such activities described 

above include preliminary work relevenant to the 

proposed LSST, the Pierre Auger observatory, and 

VERITAS.
53

Program Planning: 

Federal Advisory Committee Act 

(FACA) Committees

Department of Energy: To ensure that resources are 

allocated to the most scientifically promising research, 

the Department of Energy and its national user 

facilities actively seek external input using a variety 

of advisory bodies and directly obtain advice through 

the federally chartered Nuclear Sciences Advisory 

Committee (NSAC), the High Energy Physics Advisory 

Panel (HEPAP) and Federal Advisory Committee Act 

(FACA) committees associated with other Offices.

NSAC provides advice to the Department of Energy 

and the National Science Foundation on a continuing 

basis regarding the direction and management of the 

national basic nuclear sciences research program. 

NSAC regularly conducts reviews of university and 

national laboratory facilities to assess their scientific 

productivity, major components of the Office’s research 

program, and evaluates the scientific case for new 

facilities.

One of the most important functions of NSAC 

is development of long-range plans that express 

community-wide priorities for the upcoming decade 

of nuclear physics research. NSAC, on a rotating 

schedule, reviews the major elements of the nuclear 

physics program. These reviews examine scientific 

progress in each program element against the previous 

long-range plan, assess the scientific opportunities, and 

recommend reordering of priorities based upon existing 

budget profiles. Facility directors seek advice from 

Program Advisory Committees (PACs) to determine the 

allocation of scarce scientific resources, the available 

beam time, and to evaluate and plan their programs.

The High Energy Physics program is guided by the 

federally chartered High Energy Physics Advisory 

Panel (HEPAP), which reports both to the DOE and 

NSF. This panel, made up of leading members of the 

community, gathers information from the scientific 

community and provides advice on the direction and 

management of the field. The HEPAP panel meets 

at least three times per year and reviews scientific 

progress, assesses opportunities and the case for new 

facilities and projects, taking into account funding 

projections and program priorities. An important 

function of HEPAP is the development of long-range 

plans that reflect the community-wide priorities and 

future planning, through specially chartered subpanels.

Recommendations on including a project in the 

HEP program are made to HEPAP by the advisory 

panels described below, taking into account scientific 

merit, impact on the program, funding availability 

and program priorities. The Particle Physics Project 

Prioritization Panel (P5) is a subpanel that meets as 

needed to provide advice on prioritizing particular 

projects. The laboratory director’s assess their own 

current programs and recommend plans for the future 

via Program Advisory Committees (PAC), which 

include in-house and independent members. The 

Scientific Assessment Group for Experimental NonAccelerator Physics (SAGENAP) panel, made up 

of expert members of the community, usually meets 

yearly to provide advice on the scientific merit of 

proposed projects not using the major accelerator 

facilities. Additional information regarding program 

planning and scientific opportunities is provided 

by specially chartered panels, such as the National 

Research Council’s Committee on Physics of the 

Universe which produced the Connecting Quarks 

with the Cosmos report. The newly established FACA 

committee, the Astronomy and Astrophysics Advisory 

Committee (AAAC), designed to provide advice to 

NSF and NASA, will also provide guidance to DOE on 

areas where the programs overlap.

A Committee of Visitors to review the management 

practices of the Nuclear Physics program and the High 

Energy Physics program will be appointed under the 

guidance of NSAC and HEPAP. In particular, they 

will look at the decision process for awarding grants 

and supporting laboratory research groups, facility 

operations, and construction projects.

National Aeronautics and Space Administration:

The NASA Office of Space Science maintains the 

federally chartered Space Science Advisory Committee 

under the auspices of the NASA Advisory Council; 

the chair of the Space Science Advisory Committee 

is a member of the NASA Advisory Council. The 

Space Science Advisory Committee gathers input 

from the external scientific community on mission 

priorities, strategic planning, and ongoing activities. 

It has subcommittees corresponding to the space 

science theme areas defined by the NASA strategic 

plan. Researchers selected broadly from the scientific 

community constitute the membership of the various 

subcommittees.

The Structure and Evolution of the Universe 

Subcommittee advises NASA on science areas relevant 
54

to the physics of the universe, including cosmology, 

Dark Energy, gravity, and the use of the universe as a 

laboratory for fundamental physics.

The Office of Space Science strategic planning 

process is based on roadmaps for each of the space 

science theme areas, and it feeds into NASA’s 

agency-wide planning process. The Space Science 

Advisory Committee oversees the creation of the 

Space Science Strategy, takes into account the National 

Research Council’s decadal reviews of astronomy and 

astrophysics and other reports, and seeks NRC review 

of its strategy. The Structure and Evolution of the 

Universe Subcommittee oversees the development of 

the Structure and Evolution of the Universe Roadmap 

through a roadmap working group. The roadmap 

working group provided advice for activities and 

priorities within the Beyond Einstein Initiative. These 

priorities are incorporated in both the Space Science 

Strategy and the NASA Strategic Plan.

National Science Foundation: Planning processes at 

the National Science Foundation receive significant 

attention by the National Science Board and the 

FACA advisory committees for Mathematical and 

Physical Sciences and the Office of Polar Programs. 

The newly chartered Astronomy and Astrophysics 

Advisory Committee provides advice in this specific 

area to both NSF and NASA, with emphasis on areas 

of overlap and complementarity. An expansion of 

the membership of this committee has added an 

interface to DOE-sponsored research in astronomy 

and astrophysics, which will be a material aid to the 

program discussed here. All these advisory groups are 

guided by the National Research Council’s decadal 

reviews of astronomy and astrophysics, a communitybased planning process that has been in place for four 

decades. The NRC study Connecting Quarks with 

the Cosmos has provided specific input to planning in 

this area. In addition, the Division of Physics draws 

relevant input and advice through its participation with 

the High Energy Physics Advisory Panel (HEPAP) and 

the Nuclear Science Advisory Committee (NSAC), 

both co-sponsored with DOE.
55

Appendix II. Technical Glossary

Accelerating Expansion: the surprising fact that 

the expansion of the universe is accelerating, not 

decelerating. This can be seen in the study of distant 

supernovae, whose light appears dimmer than expected 

because the region of the explosion and our region of 

space are moving apart faster than expected.

Accretion: accumulation of dust and gas on larger 

bodies such as stars and planets. The combined 

effects of gravity and rotation often force the accreting 

material into an orbiting accretion disk.

Antiparticle: an elementary particle that has mass and 

some other properties identical to a given particle but 

has still other properties, such as charge, reversed. 

For example, the positron with positive charge is the 

antiparticle of the electron, which has negative charge 

but is otherwise the same. When an antiparticle and 

a particle meet they annihilate each other, producing 

lighter particles and the release of energy.

Axion: a Dark Matter candidate. This particle 

is postulated to explain why charge parity (CP) 

invariance holds in the strong interactions but not the 

weak. It would be a very light particle with a rest 

energy of only a fraction of an electron volt. Axions 

might have been created in large numbers, at rest, in the 

early universe.

Baryon: a strongly interacting particle made of three 

quarks. The proton for example is made of two up 

quarks and one down quark. (See quark.)

Big Bang: a theory of cosmology in which the 

expansion of the universe is presumed to have begun 

with a primeval explosion. It is supported by observed 

expansion of the universe, observed cosmic background 

radiation (see CMB), and agreement with observations 

of the calculation of the primordial abundances of light 

elements produced (See Energy generation).

Black Hole: a region of space where the gravitational 

pull is so strong that, classically, no light can escape. 

A Black Hole can form when a massive star undergoes 

gravitational collapse.

Boson: a particle whose intrinsic angular momentum 

is measured in integer units (see Spin). Examples are 

the photon and the gluon. Particles associated with all 

fundamental interactions (forces) are bosons.

Charge Parity (CP) Invariance: used to explain the 

excess of matter over antimatter. This refers to a 

property of reaction rates being the same if each 

particle is changed to its antiparticle and the process 

is reflected in a mirror. This is known not to hold 

for some weak interactions. And it is required not to 

hold for some interactions in order to explain why all 

matter and antimatter, created in equal amounts, didn’t 

annihilate after the Big Bang.

Cherenkov Radiation Detector: a detector to measure 

the speed, energy and direction of a particle. Light 

travels more slowly in material such as water than in a 

vacuum. A high energy particle passing through such a 

medium, with a speed greater than the speed of light in 

that medium, will radiate. The radiation forms a cone 

expanding outward similar to the shock pattern of a 

supersonic airplane. Observing it permits determining 

the direction of the particle and its energy.

Color: a property of quarks and gluons analogous to 

electric charge. Just as a particle with positive electric 

charge can join with a particle with negative charge to 

form an electrically neutral pair, a color neutral particle 

can be made of a quark-antiquark pair. It is not related 

to usual use of the word “color”. Quarks come in three 

colors; gluons in eight shades. Color is “confined,” 

that is colored particles are never observed directly. 

Cosmic microwave background (CMB) radiation:

residual light from the Big Bang that we see today. The 

wavelength is now expanded (or cooled or lowered 

in energy) to the microwave range. If the universe 

once was very hot, then electrons could not bind to 

protons to form a neutral hydrogen atom, the main 

constituent of the universe. This dissociation must 

have produced radiation. When the expanding universe 

became cool enough, the electrons must have found 

the protons and made neutral atomic hydrogen, at 

which point the radiation could travel without further 

interaction. “Cool enough” must have occurred about 

380,000 years into the expansion. The wavelength 

of this light is now in the microwave region. This 

microwave background was detected in the 1960s. It is 

phenomenally regular. It looks the same, to about one 
56

part in a hundred thousand, from all directions. This 

regularity is a major mystery whose explanation may 

be inflation. Although the CMB is nearly uniform, 

there are tiny fluctuations in its temperature due to 

variations in the density of the early universe. These 

tiny fluctuations grew to form galaxies.

Cosmic rays: protons, nuclei of heavy atoms, and 

possibly other particles that have been accelerated to 

high energies by astrophysical processes in the universe 

and impinge upon Earth. 

Cosmological constant (Λ): a possible term in 

Einstein’s equations of General Relativity. It can be 

interpreted as the energy density associated with the 

vacuum (empty space). 

Cosmological Principle: the assumption that, if 

considered in large enough units, the universe is the 

same everywhere (homogeneous) and in all directions 

(isotropic). 

Cosmology: the astrophysical study of the history, 

structure, and dynamics of the universe.

Dark Energy: a net energy associated with the vacuum 

(empty space) suggested by recent astronomical 

observations of type Ia supernovae. A large 

enough positive vacuum potential energy leads to 

a gravitational repulsion, making the expansion 

of the universe accelerate, whereas particles, even 

massless ones, possess gravitational attraction making 

it decelerate. A positive potential energy could 

be a constant in time or could be due to a varying 

quintessence field originating from high energy 

physics.

Dark Matter: form of matter that does not emit enough 

light or other electromagnetic radiation for it to be 

directly observable. We see many clusters of galaxies 

that appear to be gravitationally bound, but, if we count 

up the mass in their stars, the cluster doesn’t have 

enough ordinary matter to be gravitationally bound. 

We also see a few stars orbiting around the bright parts 

of galaxies, but going faster than the visible matter of 

the galaxy would imply. Additionally, gravitational 

lensing (see gravitational lensing) indicates more mass 

than is visible in many clusters. Finally, we know, 

from the amount of deuterium (heavy hydrogen) left 

over from primordial helium production (see energy 

generation) that this matter cannot be made of protons 

and neutrons. These astronomy discoveries have 

sparked major laboratory and theory efforts to discover 

new elementary particles that could constitute the 

Dark Matter and to determine how the Standard Model 

of Particle Physics must be modified to fit them in. 

About 25% of the total matter-energy budget in the 

universe is believed to be of this type. Hot Dark Matter 

(particles moving at near light speed) is not considered 

tenable; warm Dark Matter (particles recently slowed 

by the expansion of the universe) is also considered 

unlikely.

Doppler Effect: phenomenon in which an observer 

receives sound and light from bodies moving away 

with lower frequency and longer wavelength than 

emitted (see redshift) and from bodies moving toward 

the observer with higher frequency and shorter 

wavelength. The shift (fractional change) in frequency, 

or the Doppler effect, increases as the speed of the 

body increases. 

Double beta decay: a nuclear decay process in which 

two electrons are emitted. It is “doubly weak” and 

devilishly difficult to observe, but could be rich in 

information

Dust: micron and submicron-sized solid particles (dust 

grains) which account for roughly 1% of the mass of 

the space between stars and which obscure visible light. 

“Grey dust” would have a distribution in particles size 

such as to affect all wavelengths of light equally.

Electromagnetic radiation: radiation consisting 

of electric and magnetic fields vibrating with a 

characteristic wavelength or frequency. Long 

wavelengths (low frequencies) correspond to radio 

radiation; intermediate wavelengths, to millimeter 

and infrared radiation; short wavelengths (high 

frequencies), to visible and ultraviolet light; and 

extremely short wavelengths, to X rays and gamma 

rays. Most astronomical observations measure some 

form of electromagnetic radiation.

Electron Volt (eV): measure of the energy of an 

elementary particle. The 120 volts provided by a U.S. 

wall plug would permit accelerating an electron to 120 

eV of (kinetic) energy. Today’s electron accelerators 

permit accelerating electrons to hundreds of MeV (a 

million electron volts). Protons can be accelerated to a 

trillion eV (TeV). Xrays are in the kilo eV range (keV).

Energy Generation: processes by which light from the 

sun, supernovae, and formation of the light elements 

in the early universe occur. In nuclear fusion light 

nuclei, at high temperatures and pressures, combine 
57

to form heavier and more tightly bound nuclei. Stars, 

for most of their lives, change hydrogen to helium, 

thereby releasing energy in the form of visible light 

and neutrinos. When it runs out of hydrogen, a 

single, not too massive star will become a slowly 

cooling white dwarf. But about half the stars are in 

pairs, or binary systems. A binary white dwarf will 

get additional hydrogen from its neighbor and make 

more helium. When it has made just enough, it burns 

helium to heavier elements explosively making a 

bright supernova of type Ia. Assuming that “just 

enough” is the same for nearby Ia supernovae as it is 

for far away ones, these provide the standard candles

(supernovae of known intrinsic brightness) that 

showed the expansion of the universe is accelerating. 

Stars of masses many times that of the Sun suffer a 

different fate. For them, the core runs out of hydrogen 

before the outside does and starts to shrink under its 

own weight. This increases the density in the core 

sufficiently that neutrinos are produced copiously 

and help blow off a lot of the outer parts (type II 

supernova). The remaining matter then continues 

collapsing. For a sufficiently massive star, there is no 

known mechanism to stop the collapse and a Black 

Hole results. In the early universe, at about one second 

into the Big Bang, there were about six times as many 

protons as neutrons, with the neutrons slowly decaying 

(see quantum field theory). At about three minutes, 

the temperature cooled to the point that neutron plus 

proton can make heavy hydrogen (deuterium) that 

isn’t knocked apart before it is burned to helium. We 

get the right answer for the observed ratio of helium 

to hydrogen and a permissible range for the ratio of 

protons to cosmic background photons from primordial 

deuterium measurements.

Equivalence principle: a fundamental principle of 

General Relativity, one of whose consequences is that 

all objects (and light) fall in a gravitational field in the 

same way independent of their internal structure or 

other properties.

Event Horizon: the surface surrounding a Black Hole. 

It is like the “roach motel,” allowing matter or signals 

to flow in but not out.

Expanding Universe: a natural solution of the equations 

of Einstein’s theory of General Relativity. Only in 

the 20th century did we learn that stars are collected 

together into large collections, called galaxies, and 

that the galaxies are all moving away from us—with 

the ones further away moving faster. It is the redshift

(see also special relativity) that makes it clear that the 

further away the galaxy, the faster it is receding. If 

you had a movie of the expansion of the universe and 

ran the movie backward, you would see the universe 

getting denser and denser (and hotter and hotter 

because the wavelength of photons would be getting 

shorter implying higher frequency which, in turn means 

more energy). Running it forward is the Big Bang. If 

the universe expanded from a much hotter and denser 

state, there should be some observable “relics.” There 

are: the cosmic microwave background, the ratio of 

primordial helium to hydrogen (see energy generation) 

and possibly, inflation.

Family: a grouping of fermion particles. When grouped 

by their properties fermions (leptons and quarks) 

naturally fall into pairs of doublets know as families or 

generations. At present three families are known. All 

ordinary matter is made up of the leptons and quarks in 

the first family. i.e., the electron, electron neutrino, up 

quark, and down quark. 

Fermion: particles that have intrinsic angular 

momentum (see Spin) measured in half integer (1/2, 

3/2,...) units. As a consequence of this peculiar 

angular momentum, fermions obey a rule called the 

Pauli Exclusion Principle, which states that no two 

fermions can exist in the same state at the same time 

and place. This rule affects the properties of ordinary 

matter. Quarks, electrons, neutrinos, protons, and 

neutrons are fermions.

Field: mathematical specification of some property at 

every point in some space. Example 1: Earth surface 

temperature field—temperature at every point on 

the surface of the Earth. Example 2: Electric field at 

every point in spacetime. Example 3: Electron field at 

every point in spacetime. The quantum of the electric 

(electromagnetic) field is the photon; the quantum of 

the electron field is the electron. See quantum field 

theory.

Gamma rays: the most energetic form of 

electromagnetic radiation, with wavelength much 

shorter than X rays. Gamma ray bursts are transient 

intense bursts of gamma radiation lasting only a few 

seconds.

General Relativity: the theory of gravitation developed 

by Albert Einstein in which gravity is the result of 

curved geometry of space and time. General Relativity 

treats observers with relative accelerations, notes that 

you can’t tell the difference between being accelerated 
58

(say, up) and gravity pulling you (down), and it relates 

the very geometry of space to the distribution of mass 

and energy in it. Mass and energy make space curved, 

giving rise to such important effects as the bending 

of light passing near massive objects—which permits 

gravitational lensing,” tomography by distant light 

sources of galaxy clusters between us and the source—

as well as Black Holes, regions of such high mass 

density that not even light can escape.

Gluon: a massless particle that carries the strong force. 

Quarks interact via exchange of gluons. (Also see 

color.)

Grand Unification: see Unification.

Gravitational lensing: a consequence of Einstein’s 

theory of General Relativity is that the path of 

light rays can be bent by the presence of matter. 

Astronomers have observed that the light from a distant 

galaxy or quasar can be “lensed” by the matter in, 

say, an intervening galaxy to form multiple and often 

distorted images of the background object.

Graviton: the as yet undetected massless quantum

particle that carries the gravitational force.

Hadron: Particle with strong interactions: see Standard 

Model. Hadrons are either mesons (bosons) or baryons

(fermions).

Inflation: a period of accelerated expansion in the first 

very small fraction of a second of the Big Bang. This 

is postulated, inter alia, to explain why the cosmic 

microwave background radiation (see CMB) from 

different directions is so similar. Einstein’s equations 

of General Relativity tell us how fast the universe 

expands given the energy per unit volume. If that 

energy were always due to matter or radiation, the 

origin of the microwave background radiation coming 

from one direction would never be within the light 

travel distance of that coming from a direction off 

by a few degrees. How could the distribution of 

radiation by wavelength be the same to within one 

part in a hundred thousand? The leading contender 

for the explanation is that there was a period in the 

very early universe when the potential energy of some 

slowly varying field dominated the energy content, and 

expansion accelerated exponentially so that the entire 

visible universe is descended from a single, really

small region. If this picture is correct, slight quantum 

fluctuations in the inflation field grew into today’s 

galaxies.

Interferometer: an instrument in which the 

electromagnetic radiation from a celestial object along 

two different paths is collected and then brought 

together to form an interference pattern of alternating 

bright and dark bands.

Ionization: the process of an atomlosing one or more 

electrons.

Isotope: forms of an element in which the nuclei have 

the same number of protons but different numbers of 

neutrons.

Kinetic Energy: energy of motion of a particle; energy 

associated with time and space variations of a field.

Leptons: fundamental particles of matter, such 

as electrons and neutrinos. Quarks (with strong 

interactions) and leptons (without them) are the two 

building blocks of familiar matter. There are three 

families, each with a pair of quarks and a pair of 

leptons, in the Standard Model.

Light: see Electromagnetic radiation.

Light Curve: the light intensity from an object as a 

function of time. This is a big piece of the available 

information in understanding what is happening in the 

object. 

Light year: distance light travels in a year (about 10 

trillion kilometers or 6 trillion miles).

Meson: unstable, integer-spin particle made of a quarkantiquark pair. Mesons do not exist in ordinary matter. 

They have been seen in the laboratory and cosmic rays. 

An example is the pion.

Microwave: see Electromagnetic Radiation.

Neutrino: a very light particle emitted in the process 

of radioactive decay. It is a lepton. A sterile neutrino 

would be one that is not paired up with one of the three 

charged leptons in the standard model. In a neutrino 

oscillation, a neutrino of one type (electron, muon, tau) 

changes into a neutrino of another type. A Majorana 

neutrino would be one that is its own antiparticle.

Neutron star: a supernova remnant of low enough mass 

not to collapse to a Black Hole but of sufficiently high 

density and pressure that its atoms have been crushed 

until the nuclei merged and most of the electrons 

squeezed onto the protons. This releases neutrinos 

and forms a neutron-rich material. This imploded 
59

core contains about the mass of the Sun in less than a 

trillionth of the Sun’s volume.

Photon: a quantum of electromagnetic energy; the 

massless particle that carries the electromagnetic force.

Pauli Exclusion Principle: see fermion.

Polarization: the nonrandom distribution of electric 

field direction among the photons in a beam of 

electromagnetic radiation. The electric field of a 

photon beam is always perpendicular to the beam 

direction. If it is some percentage along some 

particular perpendicular direction it is said to be that 

percentage “linearly polarized” along that direction.

Potential Energy: energy stored in the position of a 

particle (e.g., near another particle of the same charge) 

or, for a field, stored in the interaction of that field with 

itself or other fields.

Pulsar: a spinning neutron star that emits radiation in 

a beam. The sweeping action of the beams causes the 

object to pulse regularly when viewed by an observer, 

just as with a lighthouse.

Quantum: a discrete unit used to describe particles on 

the atomic or smaller scale. For example light energy 

(light waves) exists in discrete quantum units called 

photons.

Quantum Field Theory: a theory that allows reliable 

calculations of weak and electromagnetic interactions. 

Each particle is associated with a mathematical field. 

The math permits calculating rates for processes. 

When you shake a charged particle, a photon, the 

quantum of light, is emitted. The nucleus of an atom, 

made of protons and neutrons, is held together by 

a “strong force.” When you shake a neutron or a 

proton, a pion is emitted. In addition to the strong and 

electromagnetic forces, there is a weak force that is 

responsible for decay of unstable particles, including 

the neutron, which if taken from a nucleus, decays 

in about 10 minutes into a proton, an electron, and a 

neutral neutrino. We know the force is weak because 

10 minutes is so long on an atomic time scale. If you 

shake a weakly-interacting particle, you get W and/or 

Z bosons emitted. We thus have three forces, strong, 

weak, and electromagnetic. The strong interactions 

are more complicated. Indeed, protons, neutrons, pi 

mesons, and other strongly interacting particles turn out 

to be made of more elementary particles called quarks, 

held together by forces whose quanta are called gluons 

in a way too complicated for us to have yet devised a 

satisfactory calculus. Gravity is in even worse shape. 

Quantum gravity is complicated by gravity itself being 

a source for gravitons and is plagued by calculational 

infinities—currently.

Quantum Fluctuation: a spontaneous fluctuation of 

energy in a volume of space. It is a consequence of the 

uncertainty principle which allows the brief formation 

of virtual particle pairs (one of matter and one of 

antimatter). In the very earliest fractions of a second of 

the Big Bang, fluctuations in space occurred and after 

the likely period of rapid expansion (see inflation), 

remained as irregularities in space. From these seeds 

eventually grew the structures in the universe such as 

galaxies.

Quantum mechanics: a mathematical framework for 

describing physics at atomic and smaller length scales, 

where energy exists in discrete “quantum” units. A 

planet, with the right speed, can orbit a star at any 

distance from the star; a continuum of energies is 

possible. However electrons, in an atom, can only be 

in discrete energy states. Among the many effects that 

follow from this quantization is spectroscopy. After 

an atom is excited to a higher energy state, it will 

return to a lower one by emitting a photon, light, of a 

specific wavelength (specific energy difference implies 

specific light frequency which implies specific light 

wavelength). The wavelength depends on the element 

to which the atom belongs. This effect allows chemical 

analysis of stars and galaxies far, far away.

Quark: a fundamental constituent of ordinary matter. 

Protons and neutrons are made of three quarks bound 

very tightly by the strong force carried by gluons. 

There are six “flavors” or kinds of quarks called up, 

down, charm, strange, top and bottom. They are 

distinguished by properties such as charge and mass.

Quark-Gluon Plasma: matter at sufficiently high 

temperature and density that atoms are dissociated into 

elections and nuclei; nuclei are dissociated into protons 

and neutrons; and protons and neutrons are dissociated 

into quarks and gluons. This was the case before about 

a ten thousandth of a second into the Big Bang. 

Quintessence: name given to field models proposed as 

possible explanations for the accelerating expansion 

of the universe. A small, but non-zero, uniform 

quintessence field permeating all space and only 

decreasing in time extremely slowly could produce 

an effective, time-dependent cosmic energy density 
60

accompanied by a sufficiently negative pressure to 

cause the observed acceleration of the expansion of the 

universe.

Redshift: (1) the Doppler redshift is a shift toward 

longer wavelengths of spectral lines in the radiation 

emitted by an object caused by relative motion of 

the emitting object away from the observer: (2) the 

gravitational redshift is a shift to longer wavelengths of 

spectral lines emitted by a body in a gravitational field 

when viewed by an observer in a weaker gravitational 

field.

Rest Energy: energy stored in the mass of a particle at 

rest. If the particle decays, the energies of the decay 

products must add up to the rest energy of the decaying 

particle.

Spectroscopy: the technique whereby light is broken up 

into its constituent colors by a prism or other device. 

Different chemical elements can be distinguished by 

the different color lines, or spectral lines, they emit 

when their atoms are excited. See quantum mechanics.

Special Relativity: Einstein’s theory of spacetime 

structure to account for the fact that the speed of light is 

a universal constant and does not depend on the relative 

motion between the observer and the light source. 

The principle of special relativity is that two different 

observers, moving with constant relative velocity find 

the same speed for a light signal. This implies that 

their clocks and length measurements will disagree in 

just such a way as to ensure agreement on the speed of 

light. An important effect for astronomy is that light 

from a source moving away from you appears more 

red, i.e., appears shifted to longer wavelength.

Spin: intrinsic angular momentum of quantum 

particles. All particles are grouped into those that have 

spin given in half integer units (fermions) or in whole 

integer units (bosons).

Standard candle: any luminous celestial object of a type 

which is more or less constant (from object to object) 

in absolute magnitude (intrinsic brightness). It can be 

used to gauge distances, because the further away it is, 

the fainter it will appear.

Standard Model of Cosmology: the current 

understanding that the universe is expanding and 

has been ever since a state of very high density and 

temperature. See Big Bang.

Standard Model of Particle Physics: the model of 

fundamental particles and interactions presenting all 

the observed particles and their processes through 

the strong, weak, and electromagnetic interactions 

of quarks and leptons. It explains the forces that 

hold atoms and nuclei together or lead to their 

decay. More than three decades of theoretical and 

experimental effort went into establishing it. The 

Standard Model has three families (and three colors). 

The first family consists of the “up quark,” the “down 

quark,” the electron, and the electron neutrino. Up 

and down have strong, weak, and electromagnetic 

interactions (mediated by gluons, the photon, and the 

W and Z, respectively); the electron has weak and 

electromagnetic, and the neutrino has just the weak. 

The electron and neutrino are termed leptons. There 

are two additional families of more massive quarks 

and leptons. The quarks of each family come in three 

colors. The gluons come in eight shades and bind 

the quarks into observable particles that are “color 

neutral” (just as you can make white light out of the 

primary colors). This binding (color confinement) 

means the strong gluon force must be quite strong 

indeed, explaining why we are having so much trouble 

computing strong interactions of observable particles. 

There is a kind of mixing of the three families of 

quarks. We are also just in the process of discovering 

“mixing” of the three families of neutrinos and small, 

but non-zero, neutrino masses. This mixing explains 

a problem we have had since the mid 60s—not seeing 

enough neutrinos coming from the Sun, which gets 

its energy from changing four protons into a helium 

nucleus, neutrinos, and photons. We have some ideas 

about unification of the three forces at high energies, 

but can’t yet fit gravity into the schemes.

String theory: a highly mathematical and not easily 

tested theory that appears to resolve the incompatibility 

between General Relativity and quantum mechanics 

and to unify them.

Sunyaev-Zeldovich Effect: a method of using a hot 

cloud of ionized hydrogen gas as a standard candle. 

Scattering of the CMB photons off the energetic 

electrons in the cloud distorts the CMB coming from 

the direction of the cloud. Collisions of the energetic 

electrons make X rays. Combining observations 

of both permits deducing the size, intrinsic X-ray 

brightness and distance of the cloud.

Supernova: catastrophic stellar explosion in which so 

much energy is released that the supernova alone can 
61

outshine for weeks an entire galaxy of billions of stars. 

The mechanism of explosion depends on which of two 

types of supernova it is. A type II supernova explosion 

signals the death of a massive star that has run out of 

nuclear fuel. The core collapses, and either a neutron 

star remains or a Black Hole is produced. A type Ia 

supernova is an explosion of a smaller star that is being 

fed fuel from a companion star. Type Ia supernovae 

are important standard candles because they explode at 

about the same mass with about the same brightness.

Supersymmetry (SUSY): a space-time symmetry that 

would imply the existence of partners to all elementary 

particles, with quantum spins of one-half a unit higher 

or lower.

Ultra High Energy Cosmic Rays (UHECRs): particles 

coming from outside our galaxy with energies 

more than a million times those that our highestenergy accelerators can produce. These are telling 

us something about astrophysical processes, but we 

don’t yet know what. Cosmic rays, mostly protons, 

impinge on the earth from all directions. There are 

fewer at higher energies, but, at high enough energies, 

they must lose energy by interacting with the cosmic 

microwave background—unless they are produced 

relatively close to us (not too many galaxies away). 

We are seeing too many ultra high energy ones that 

shouldn’t get here, 50 or so over several decades with 

current and past detectors. The new Pierre Auger 

detector will start seeing perhaps 1,000 per year in a 

few years, permitting detailed study of such properties 

as distribution in energy and direction.

Uncertainty Principle: principle that is not possible to 

know with unlimited precision both the position and 

momentum of a particle.

Unification: idea that the strong, weak, 

electromagnetic, and gravitational interactions are 

different aspects of a single universal interaction, which 

would be seen at extremely high energies. An example 

of this kind of approach is the unification of electricity 

and magnetism by Maxwell in 1865 into one theory of 

electromagnetism. In the late 1960s, electromagnetism 

and the weak interactions were successfully unified and 

in the 1970s, Grand Unification theory extended the 

idea to the strong interactions.

Vacuum: space empty of particles and radiation. A 

perfect vacuum would contain no atoms or molecules. 

There is no reason why a perfect vacuum should have 

zero energy; recent observations can be explained by a 

very small: (1) constant vacuum energy or (2) potential 

energy of a quintessence field.

Virtual: name given to an elementary particle that exists 

only for an extremely brief instant as an intermediary in 

a process. The particle is “exchanged” in an interaction 

but cannot be directly observed because its energy is 

less than its rest energy. Such particles are thought to 

pop in and out of existence for a brief moment, but are 

not freely propagating and cannot be observed.

Weak force: one of the four fundamental forces, which 

also include strong force, electromagnetism, and 

gravity. The weak force causes radioactive decay.

White dwarf: a very small star in an advanced state 

of stellar evolution. A white dwarf is created when 

the star finally exhausts its possible sources of fuel 

for thermonuclear fusion. The star collapses under its 

own gravity. But the collapse is stopped by the Pauli 

Exclusion Principle among its electrons. White dwarfs 

are typically about the size of the earth. The Sun will 

become a white dwarf in about five billion years.
62

Appendix III. Acronyms

AAAC: Astronomy and Astrophysics Advisory 

Committee

ACS: Advanced Camera for Surveys instrument on the 

Hubble Space Telescope

ACT: Atacama Cosmology Telescope

AMANDA: Antarctic Muon And Neutrino Detector 

Array

AMS: Alpha Magnetic Spectrometer experiment

ATLAS: Argonne Tandem Linac Accelerator System 

BOREXino: A Real Time Detector for Low Energy 

Solar Neutrinos at the National Laboratory of Gran 

Sasso, Italy

CBI: Cosmic Background Imager

CDMS II: The Cryogenic Dark Matter Search II 

experiment 

CEBAF: Colliding Electron Beam Accelerator Facility

CERN: European Laboratory for Particle Physics

CMB: Cosmic Microwave Background radiation

Con-X: The Constellation X-ray Observatory 

CP: charge-parity symmetry

DASI: The Degree Angular Scale Interferometer 

DOE: The Department of Energy

ESA: European Space Agency

EUSO: Extreme Universe Space Observatory

eV: Electron volt

FACA: Federal Advisory Committee Act

Fermilab (or FNAL): Fermi National Accelerator 

Laboratory

FES: Office of Fusion Energy Science

GLAST: Gamma-ray Large Area Space Telescope

GPB: Gravity Probe B

HED: High Energy Density

HEDP: High Energy Density Physics

HEP: High Energy Physics

HEPAP: High Energy Physics Advisory Panel

HiRes: High Resolution Fly's Eye project

HRIBF: Holifield Radioactive Ion Beam Facility

HST: Hubble Space Telescope

IceCube: Under-ice telescope at the South Pole

ICF: Inertial Confinement Fusion

INTEGRAL: INTErnational Gamma Ray Astrophysics 

Laboratory

IWG: Interagency Working Group

JDEM: Joint Dark Energy Mission

K2K: From KEK to Kamioka long baseline neutrino 

oscillation experiment

KamLAND: Kamioka Liquid scintillator Anti-Neutrino 

Detector

KEK: Japanese abbreviation for High Energy 

Accelerator Research Organization

LBNL: Lawrence Berkeley National Laboratory 

LHC: Large Hadron Collider

LIGO: Laser Interferometer Gravitational wave 

Observatory

LISA: Laser Interferometer Space Antenna

LSST: Large-aperture Synoptic Survey Telescope

MILAGRO: Multiple Institution Los Alamos Gamma 

Ray Observatory
63

MiniBooNE: Mini Booster Neutrino Experiment

MPS: NSF’s Math and Physical Science Directorate

MREFC: NSF’s Major Research Equipment and 

Facilities Construction account

NAS: National Academy of Science

NASA: National Aeronautics and Space Administration

NIF: National Ignition Facility

NIST: National Institute of Standards and Technology

NNSA: National Nuclear Security Administration

NP: DOE's Office of Nuclear Physics

NRC: National Research Council

NSAC: Nuclear Sciences Advisory Committee

NSCL: National Superconducting Cyclotron 

Laboratory at Michigan State University

NSF: National Science Foundation

NSTC: National Science and Technology Council

NUMI/MINOS: Neutrinos at the Main Injector/Main 

Injector Neutrino Oscillation Search

OMB: Office of Management and Budget

OPP: NSF Office of Polar Programs

ORNL: Oak Ridge National Laboratory

OSS: NASA Office of Space Science

OSTP: Office of Science and Technology Policy

P5: Particle Physics Project Prioritization Panel

PAC: Program Advisory Committee

PCA: Program Commitment Agreement

Pierre Auger: High energy cosmic ray detector array

QED: Quantum Electro-Dynamics

QGP: Quark Gluon Plasma

R&D: Research and Development

RHIC: The Relativistic Heavy Ion Collider

RIA: Rare Isotope Accelerator

RXTE: Rossi X-Ray Timing Explorer

S&T: Science and Technology

SAGENAP: Scientific Assessment Group for 

Experimental Non-Accelerator Physics

SciDAC: Scientific Discovery through Advanced 

Computing

SDSS: The Sloan Digital Sky Survey

SEU: NASA's Structure and Evolution of the Universe 

theme

SEUS: The NASA Structure and Evolution of the 

Universe Subcommittee

SLAC: Stanford Linear Accelerator Center

Sne Ia: type Ia supernovae

SNO: Sudbury Neutrino Observatory

SPASE: South Pole Air Shower Experiment

SPT: South Pole Telescope

SQUID: Superconducting QUantum Interference 

Device

Super–K: Super Kamiokande experiment

SZ: Sunyaev-Zel'dovich

TeV: trillion electron volts

TeVatron: Proton antiproton collider at Fermilab

UHECR: Ultra High Energy Cosmic Rays

VERITAS: The Very Energetic Radiation Imaging 

Telescope Array System 

WFPC2: Hubble Space Telescope Wide Field and 

Planetary Camera 2

WIPP: Waste Isolation Pilot Plant

WMAP: Wilkinson Microwave Anisotropy Probe 

XMM-Newton: Not technically an acronym, XMM-
64

References

Department of Energy, Facilities for the Future of Science: A Twenty Year Outlook, 2003. 

High Energy Physics Advisory Panel Sub Panel on Long Range Planning, The Science Ahead, The Way to 

Discovery, Department of Energy, 2002.

National Aeronautics and Space Administration, Space Science Enterprise Strategy, 2003. 

National Research Council, Connecting Quarks with the Cosmos: Eleven Science Questions for a New Century, 

National Academies Press, Washington, D.C. 2003.

National Research Council, Neutrinos and Beyond: New Windows on Nature, National Academies Press, 

Washington, D.C. 2003.

National Research Council, High Energy Density Physics: The X-Games of Contemporary Science, National 

Academies Press, Washington, D.C. 2003.

National Research Council, Astronomy and Astrophysics in the New Millennium, National Academies Press, 

Washington, D.C. 2001.

Nuclear Science Advisory Committee, Opportunities in Nuclear Science: A Long Range Plan for the Next 

Decade, Department of Energy, 2002. 

Office of Management and Budget, The President’s Management Agenda, Executive Office of the President, 

Washington, DC: 2001.

Office of Science and Technology Policy and the Office of Management and Budget, FY 2005 Interagency 

Research and Development Priorities Memorandum, Executive Office of the President, Washington, DC: June 5, 

2003.

Structure and Evolution of the Universe Roadmap Team, Beyond Einstein: From the Big Bang to Black Holes, 

National Aeronautics and Space Administration, 2003.
65

NASA Paul Hertz

Senior Scientist for Astronomy and Physics

 Astronomy and Physics Division

 Office of Space Science

 National Aeronautics and Space Administration

 Code SZ

 300 E Street, SW

 Washington, DC 20546-0001

 Telephone: 202-358-0986

 FAX: 202-358-3096

 Email: paul.hertz@nasa.gov

Michael Salamon

Discipline Scientist for Fundamental Physics

 Astronomy and Physics Division

 Office of Space Science

 National Aeronautics and Space Administration

 Code SZ

 300 E Street, SW

 Washington, DC 20546-0001

 Telephone: 202-358-0441

 FAX: 202-358-3096

 Email: michael.h.salamon@nasa.gov

NSTC Committee on Science

Co-Chairs: Kathie Olsen, Office of Science & Technology Policy

 Elias Zerhouni, National Institutes of Health, 

 Department of Health & Human Services

 Rita Colwell, National Science Foundation

Interagency Working Group on the Physics of the Universe

Co-Chairs: Anne Kinney, National Aeronautics & Space Administration

 Joseph Dehmer, National Science Foundation

 Peter Rosen, Department of Energy

Exec. Secretary: Nicholas White, National Aeronautics & Space Administration

Michael Holland

Senior Policy Analyst

Office of Science and Technology Policy

Executive Office of the President

Washington, D.C. 20502

Telephone: 202-456-6069

FAX: 202-456-6027

Email: mholland@ostp.eop.gov

OSTP Patrick Looney

 Assistant Director, Physical Science 

 and Engineering

 Office of Science and Technology Policy

 Executive Office of the President

 Washington, DC 20502

Telephone: 202-456-6125

 FAX: 202-456-6027

 Email: jlooney@ostp.eop.gov

Anne L. Kinney

Director

Astronomy and Physics Division

Office of Space Science

National Aeronautics and Space Administration

Code SZ

300 E Street, SW

Washington, DC 20546-0001

Telephone: 202-358-2150

FAX: 202-358-3096

Email: anne.l.kinney@nasa.gov

Vigdor Teplitz

Chief

University Programs

NASA Goddard Space Flight Center

Code 600

Greenbelt, MD 20771

Telephone: 301-286-2363

Email: Vic.Teplitz@nasa.gov
66

DOE Christopher Keane

Director

 Division of Secondaries and Inertial Fusion

 U.S. Department of Energy

 NA-113.1/Forrestal Building

 1000 Independence Ave. SW

 Washington, DC 20585

 Telephone: 202-586-0852

 FAX: 202-586-8005

Email: chris.keane@nnsa.doe.gov

Dennis Kovar

 Associate Director

 Office of Nuclear Physics

 Office of Science

 U.S. Department of Energy

 SC-90/Germantown Building

 1000 Independence Avenue, S.W.

 Washington, DC 20585-1290

 Telephone: 301-903-3613

 FAX: 301-903-3833

 Email: dennis.kovar@science.doe.gov

Ronald McKnight

Senior Advisor for Inertial Fusion Energy

Office of Fusion Energy Sciences

SC-55/Germantown Building

U.S. Department of Energy

100 Independence Avenue, SW

Washington, D.C. 20585-1290

John O’Fallon

Executive Assistant for International 

 and Interagency Programs

Office of High Energy Physics

Office of Science

U.S. Department of Energy

SC-20/Germantown Building

1000 Independence Avenue, S.W.

Washington, DC 20585-1290 

Telephone: 301-903-8468

FAX: 301-903-2597

Email: john.ofallon@science.doe.gov

Eileen D. Friel

Executive Officer, Division of Astronomical Sciences

National Science Foundation

Arlington, VA 22230

Telephone: 703-292-4895

Email: efriel@nsf.gov

Joseph L. Dehmer

Director

Division of Physics

National Science Foundation

4201 Wilson Blvd., Room 1015

Arlington, VA 22230

Telephone: 703-292-7370

FAX: 703-292-9078

Email: jdehmer@nsf.gov

NSF Laura P. Bautz

 Senior Staff Associate

 Division of Physics

 National Science Foundation

 4201 Wilson Blvd., Room 1015

 Arlington, VA 22230

 Telephone: 703-292-7211

 FAX: 703-292-9078

 Email: lbautz@nsf.gov

G. W. Van Citters

Director, Division of Astronomical Sciences

 National Science Foundation

 Arlington, VA 22230

 Telephone: 703-292-4908

 Email: gvancitt@nsf.gov

NASA Nicholas White

Chief, Laboratory for High Energy Astrophysics

 NASA Goddard Space Flight Center

 Code 660

 Greenbelt, MD 20771

 Telephone: 301-286-8664

 FAX: 301-286-

 Email: Nicholas.E.White@nasa.gov
67

DOE S. Peter Rosen

 Senior Manager for Research Policy

 Office of Science

 U.S. Department of Energy

 7B084, Forrestal Building

 1000 Independence Avenue, S.W.

 Washington, DC 20585

 Telephone: 202-586-3673

 FAX: 202-586-4120

 Email: peter.rosen@science.doe.gov

 Ralph Schneider

 U.S. Department of Energy

 NA-113/Forrestal Building

 1000 Independence Ave. SW

 Washington, DC 20585

 Telephone: 202-586-0837

 FAX: 202-586-8005

 Email: Ralph.Schneider@nnsa.doe.gov

 Jehanne Simon-Gillo

 Program Manager for Facilities 

 and Instrumentation

 Office of Nuclear Physics

 Office of Science

 U.S. Department of Energy

 SC-90/Germantown Building

 1000 Independence Avenue, S.W.

 Washington, DC 20585-1290

 Telephone: 301-903-1455

 FAX: 301-903-3833

 Email: jehanne.simon-gillo@science.doe.gov

 Robin Staffin

 Associate Director

 Office of High Energy Physics

 Office of Science

 U.S. Department of Energy

 SC-20/Germantown Building

 1000 Independence Avenue, S.W.

 Washington, DC 20585-1290

 Telephone: 301-903-3624

 FAX: 301-903-2597

 Email: robin.staffin@science.doe.gov

Kathleen Turner

Program Manager

Office of High Energy Physics

Office of Science

U.S. Department of Energy

SC-20/Germantown Building

1000 Independence Avenue, S.W.

Washington, DC 20585-1290

Telephone: 301-903-1759

FAX: 301-903-2597

Email: kathy.turner@science.doe.gov

John Willis

Director, Research Division

Office of Fusion Energy Sciences

Office of Science

U.S. Department of Energy

SC-50/Germantown Building

1000 Independence Avenue, S.W.

Washington, DC 20585-1290

Telephone: 301-903-4095

FAX: 301-903-4716

Email: jwillis@fusion.doe.gov
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