# Presentation: 944039

## Recent Cosmological Discoveries: Questions & Answers

- Princeton University Class of 1957

- Scott Dodelson
-  Theoretical Astrophysics Group, Fermilab

## Breakfast with a Seven Year Old 

***Scott to Ilana***** You really should study for your spelling test. **
***Ilana***** ****	****Why? I got most of them right last time without studying. **
***Scott***** ****	****Don't you want to be the best you can be? Do you want to be mediocre? **
***Ilana***** ****	****What's 'mediocre'? **
***Scott***** ****	****Just like everyone else. **
***Ilana***** ****	****That's what I want to be: just like everyone else. **
***Scott***** ****	****You don't want to be the best? **
***Ilana***** ****	****You're not the best. **
***Scott***** ****	****I try to be the best. **
**Pause ****	**
***Ilana*****	****It's not working.**

## The Spirit Searches EverythingKeeping Life’s Questions

- More than *homo sapiens *– humans knowing, we are humans questioning – *homo quarens.*
- From the beginning of human existence, these thoughts and questions have been put in one form or another.

## Is all wholly relative?

- Rather than seeing things as they are, we see things as we are
- Contemporary physics, the concept of time, and even the elegance and apparent truths of mathematics ... are not discoveries of what is really *there* – inherent in reality – but constructs and projections of the human mind looking for patterns and rationality
- There are as many different woods and rivers as those who walk or swim
- But is all wholly relative? Is every interpretation of the same value? Is there no basis for shared understanding?

## The Universe is expanding

## Galaxies should be moving away from us, and the farther they are, the faster they should move 

- Galaxies should be moving away from us, and the farther they are, the faster they should move

- Edwin Hubble (1929)

-  Other civilizations [even those in other galaxies] see the same effect
-  Einstein did not ask astronomers to measure this!

## Light Element Production

- The early universe was hot and dense, hot enough and dense enough to be an excellent nuclear reactor

- T = One Second

- T = Two Minutes

- T=0 corresponds to temperatures/energies so high that we do not know the physical laws governing behavior: We understand the limits of our knowledge

## Hydrogen: 75%

- Helium:     24%
- Helium-3:  1 part in 10000
- Deuterium: 1 part in 100,000
- Lithium: 1 part in a billion

- _Predictions_

- _Observations_
- 	75%
- 	24%
- 1 part in 10000
- 1 part in 100,000
- 1 part in a billion

- Light Element Production

-  Other civilizations [even those in other galaxies] see the same effect
-  The work of Alpher Bethe, & Gamow (1948) was ignored for over ten years

## Cosmic Radiation

- In 1960, Bell Labs (Holmdel, NJ) researchers Penzias & Wilson took an old radio antenna (which was replaced by a satellite) and searched for radio waves from the center of our galaxy.

## They found ... no excess from Galaxy

- But a signal that was identical no matter what direction the telescope was pointed!

- They assumed it was due to ...

- So they took steps to eliminate the *white dielectric material*

## Meanwhile ... at a small school 30 miles to the west

- Robert Dicke, Peter Roll, and David Wilkinson were trying to find the radiation that should be left over from the universe’s hot early past.

## One day they received a phone call from Bell Labs

- “Well, boys, we’ve been scooped!”

## Cosmic Radiation

-  Other civilizations [even those in other galaxies] see the same effect
-  Dicke had the technological ability to detect this in the late 1940’s!

## Sound, not Light

- In many religions God’s creativity and presence to the world are intuited in terms of light that is itself invisible and silent...Steiner more often refers to sound which he imagines to be akin to the background radiation of creation... “Music, above all is the unwritten theology.”

## We see radiation today from last scattering surface when the universe was just 400,000 years old

## Small Anisotropies in the Cosmic Radiation

- Hotter than average by about 1 part in 10,000

- Cooler than average by about 1 part in 10,000

## Acoustic Oscillations

-  Pressure of radiation acts against clumping
-  If a region gets overdense, pressure acts to reduce the density: **restoring force**

## Pattern can be decomposed into Fourier modes

- +

- =

## Slide 19

## What spectrum is produced by a stringed instrument

- C string on a ukulele

## Compare the ukulele spectrum to the cosmic radiation spectrum

**KINGS I:11 **Then a great and powerful wind tore the mountains apart and shattered the rocks before the LORD, but the LORD was not in the wind. After the wind there was an earthquake, but the LORD was not in the earthquake. **12** After the earthquake came a fire, but the LORD was not in the fire. And after the fire came a gentle whisper. **13** When Elijah heard it, he pulled his cloak over his face and went out and stood at the mouth of the cave.       Then a voice said to him, "What are you doing here, Elijah?"

## Questions/Answers

- Science Questions, Religion Accepts Answers
- The Wall Street Journal, Mar 23, 2005
- Mr. [Charles H. Townes] is free to believe whatever he wants, but this particular belief is preposterous in the face of human history. **The history of the relationship between science and religion is clear: Science encourages us to ask questions; religion encourages us to accept answers.** Religion's "encouragement" has at times (including today in many parts of our world) included acts of horrific violence;theirs is a "holds barring" effort of extraordinary proportions. Elsewhere holds are barred in less extreme ways, but they are barred nonetheless. The day we experience a jihad or crusade demanding belief in the existence of DNA, maybe I'll change my mind...

- No! Science respects answers; we are no longer asking the same questions we asked 100 years ago. Questions in religion persist; answers tell us more about the person than about the question.

## We are actively pursuing other questions ...

-  Why is there not nothing?
-  What is the universe made of?

## Why is the Universe accelerating?

## Acceleration is surprising

## Mystery has broad appeal

## To get acceleration in the context of general relativity ...

- Need substance whose **energy density ** remains roughly constant as the universe expands

## Energy seems to be associated with empty space

- These quantum mechanical fluctuations give the *vacuum *an energy; perhaps it is this energy that is driving acceleration. I.e., **Perhaps nothing is something.**

## When we try to calculate the energy of the vacuum ...

- The answer we get is too big by a factor of
- 1,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000

- So, we are not done! But we believe that to understand the universe on very large scales, we need to improve our understanding of the physics of the small.

## What is the way to love and fear Him? By considering His works and His wonderful creations and seeing in them His wisdom.
			Maimonides, Code of Law

 I realize that I cannot just sit outside and observe. Each of us must participate in order to know... We may drive by the woods looking at the trees and undergrowth through the car window. Or we may stop and hike into the woods for a very different experience.

- 			*Maimonides, Code of Law*
-  I realize that I cannot just sit outside and observe. Each of us must participate in order to know... We may drive by the woods looking at the trees and undergrowth through the car window. Or we may stop and hike into the woods for a very different experience.