HDTenEightyP/NetNews huggingface dataset:
From: sichase@csa2.lbl.gov (SCOTT I CHASE)
Newsgroups: sci.physics,alt.sci.physics.new-theories
Subject: The Speed of Gravity Waves
Date: 10 Apr 92 19:46:27 GMT
Organization: Lawrence Berkeley Laboratory - Berkeley, CA, USA
Distribution: world
Reply-To: sichase@csa2.lbl.gov
NNTP-Posting-Host: 128.3.254.197
News-Software: VAX/VMS VNEWS 1.3-4   

There recently was a discussion of gravity waves and I asserted that 
the speed of such waves must necessarily be Cem, the speed of electromagnetic
waves, by virtue of the masslessness of the graviton.  I have since learned
that my answer was not complete.  Here is as better explanation:

The speed of gravitational radiation (Cgw) depends upon the specific model of
Gravitation that you use.  There are quite a few competing models, including of
course Einstein's but also Brans-Dicke and several families of others.  
All metric models can support gravity waves.  But not all predict radiation 
travelling at Cgw = Cem.

There is a class of theories with "prior geometry", in which, as I understand
it, there is an additional metric which does not depend only on the local
matter density.  In such theories, Cgw != Cem in general.

However, there is good evidence that Cgw is in fact at least almost Cem.
We observe high energy cosmic rays in the 10^20-10^21 eV region.  Such
particles are travelling at up to (1-10^-18)*Cem.  If Cgw < Cem, then
particles with Cgw < v < Cem will radiate Cherenkov gravitational radiation
into the vacuum, and deccelerate from the back reaction.  So evidence of these
very fast cosmic rays good evidence that Cgw >= (1-10^-18)*Cem, very close
indeed to Cem.  

Summary:  In a purely Einsteinian universe, Cgw = Cem.  However, a class
of models not yet ruled out experimentally does make other predictions.  

A definitive test would be produced by LIGO in coincidence with optical 
measurements of some catastrophic event which generates enough gravitational
radiation to be detected.  Then the "time of flight" of both gravitons and
photons from the source to the Earth could be measured, and strict direct
limits could be set on Cgw. 

-Scott
From: trivedi@curie.uchicago.edu (Anil Trivedi)
Newsgroups: sci.physics
Subject: A Great Book Bargain From Princeton
Date: 17 Apr 92 03:01:25 GMT
Distribution: usa
Organization: Enrico Fermi Institute, University of Chicago.


Princeton University Press has a sale going on in which a few physics
books seem to have been included as an afterthought (if you saw the
catalog, you would know what I mean). However, that very short list
includes one gem:

****************************************

	Quantum Theory and Measurement
	by Wheeler and Zurek

	(HARDCOVER)

	List= around $100
	Sale= around $40 + $3 shipping

****************************************

This is a magnificent book. A softcover version sells for $35. But for
an 850 page book, five extra dollars for the hardcover are well worth it.

To order the book,

(i)   Call 1-800-777-ISBN

(ii)  The operator will ask you which catalog you are ordering from.
      Say "Princeton Special Sale 1992".

(iii) Now the operator will ask you for something called "PSC Number"
      printed on the back of the catalog. 

      Feel free to say "1"; that's what it says on my catalog.

(iv)  Now they want the "P Number" for this book: It is "P725"
                                                         ^^^^
(v)   From now on, it's easier: address, credit card #, etc...


In case someone has been reading too fast: I AM NOT SELLING THIS BOOK!
PLEASE CALL PRINCETON UNIVERSITY PRESS DIRECTLY AT THE ABOVE NUMBER.

The catalog contains a few other interesting items in history and
philosophy of science, but for physics this is the pick of the pack.


--Anil Trivedi
From: neufeld@helios.physics.utoronto.ca (Christopher Neufeld)
Subject: Re: What is not being conserved?
Organization: University of Toronto Physics/Astronomy/CITA
Date: Fri, 17 Apr 1992 17:19:13 GMT

In article <1992Apr14.162249.17020@kakwa.ucs.ualberta.ca> anderson@fermi.phys.ualberta.ca (Warren G. Anderson) writes:
>I think everyone has been pretty much missing Kens point here (or maybe I am).
>
>Consider the following. Prepare an excited particle in a state with finite  
>uncertainty in momentum. Around the particle, put a sherical detector that 
>measures exactly (it's a thought experiment, ok :-) the momenta of massive
>particles and the position of photons. Allow the excited particle to return
>to ground state.
>
   But the particle and photon are entangled, so the momentum of the
particle and the position of the photon are non-commuting observables. By
purely mathematical consistency arguments you can show that it is not
possible, even in principle, to measure both those quantities to
arbitrary precision.

>So, it seems that I have to either abandon conservation of energy
>or Heisenberg's uncertainty principles.
>
   No, the uncertainty principle says that you couldn't manufacture such
a system in the first place. You might as well be asking about the
behaviour of a wave packet which is arbitrarily short in time, and is
also a pure single frequency. Such beasts do not exist.

>##  Warren G. Anderson


-- 
 Christopher Neufeld....Just a graduate student  | alien: n. a being who
 neufeld@helios.physics.utoronto.ca    Ad astra  | travels great distances
 cneufeld@terranet.cts.com                       | to molest our cattle
 "Don't edit reality for the sake of simplicity" | and trample our grain
From: rescorla@rtnmr.chem.yale.edu (Eric Rescorla)
Newsgroups: sci.physics
Subject: Re: simple question
Date: 8 Apr 92 19:36:55 GMT
Article-I.D.: cs.1992Apr8.193655.27457
Organization: Rescorla for himself.

In article <1992Apr08.173630.1785@watson.ibm.com> platt@watson.ibm.com (Daniel E. Platt) writes:
>In article <1992Apr8.161532.24698@cs.yale.edu>, rescorla@rtnmr.chem.yale.edu (Eric Rescorla) writes:
>The concentrations have not been ~ constant over time.
>
>See some of Colin Renfrew's work...  You'd find it interesting...
It was my impression that they had been constant to within say 50%,
which was all I meant to suggest.
-Ekr



-- 
-------------------------------------------------------------------------------
Eric Rescorla, DoD#431, Honda CM400 rider          rescorla@rtnmr.chem.yale.edu
Yale University Department of Chemistry            We hack anything.
My mind is now for rent: C/Unix,Vacuum Tech,Machining,P-Chemist. Hire me, eh?
From: sichase@csa2.lbl.gov (SCOTT I CHASE)
Newsgroups: sci.physics
Subject: FAQ LIST WILL START SOON
Date: 16 Apr 92 19:23:19 GMT
Article-I.D.: dog.22749
Reply-To: sichase@csa2.lbl.gov
Organization: Lawrence Berkeley Laboratory - Berkeley, CA, USA
NNTP-Posting-Host: 128.3.254.197
News-Software: VAX/VMS VNEWS 1.3-4

Dear Sci.Physics participants,

Thanks to all of you who have responded to my original post regarding a new 
FAQ.  In addition to the items posted here, I have received about a dozen
E-mail letters supporting my proposal and making additional suggestions, 
almost all of which were excellent and primarily pertained to topics which
should be included.

The best suggestion was that the posted FAQ summary should contain abbreviated 
answers as well as just a listing of longer contents to be found by FTP.  I
will try this approach and see if it works.

To all who volunteered to write FAQ entries - you will hear from me soon.

To all of you who wrote to warn me of the job that lies ahead - your comments
are sobering, but will not deter me from my attempt.  I hope to enlist you
all to make the job easier on me! 

Regards to All,

-Scott

--------------------
Scott I. Chase
SICHASE@CSA2.LBL.GOV
From: crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass)
Newsgroups: sci.physics
Subject: Re: People against Supercollider???
Date: 13 Apr 92 17:32:20 GMT
Distribution: na
Organization: University of Virginia

In article <22679@dog.ee.lbl.gov> sichase@csa2.lbl.gov writes:
>In article <1992Apr11.004156.19471@murdoch.acc.Virginia.EDU>, crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass) writes...
>>
>>>How fast can it turn bismuth into gold?
>>>
>> 
>>    $10 billion is over a thousand tons of gold.  It had better be pretty
>>    fast ...
>> 
>
>As a p-p collider, the SSC is poorly suited to this task.  (Note that the SSC
>is not a p-pbar collider, as is often asserted.)  However, there will be a
>small fixed-target program at much lower energy than 40 TeV in order to study 
>p-nucleus interactions at the SSC.  In this configuration, it is possible in
>principle to transmute lighter elements into gold.  However at these energies,
>nuclei tend to get blasted apart by the incoming projectile.  You need a much
>lower energy, say from a 100 MeV cyclotron, or the Bevalac, to have a
>reasonable probability of the target nucleus absorbing the incoming proton
>without ablating into nothingness.

     Can you say 'tongue in cheek', sure, I knew you could.

                                dale bass





--
C. R. Bass                                           crb7q@virginia.edu
Department of Mechanical and Aerospace Engineering
University of Virginia
Charlottesville, Virginia                            (804) 924-7926
From: pauls@trsvax.tandy.com
Date: 06 Apr 92 12:27 CDT
Newsgroups: sci.physics
Subject: SSC detectors - how??
Message-ID: <8400006@trsvax>
Nf-ID: #N:trsvax:8400006:000:290
Nf-From: trsvax.tandy.com!pauls    Apr  6 12:27:00 1992


Just a quick question:

if the SSC is supposed to find 'new' stuff, how do you detect it?

Are there any direct (first-order) measurements? Or, are all the
measurements (excuse me...observations (heh heh)) second-order??

How do you detect what you don't know beforehand what you'll find?


Newsgroups: sci.physics
From: anderson@fermi.phys.ualberta.ca (Warren G. Anderson)
Subject: Re: What is not being conserved?
Organization: University Of Alberta, Edmonton Canada
Date: Tue, 14 Apr 1992 16:22:49 GMT

I think everyone has been pretty much missing Kens point here (or maybe I am).

Consider the following. Prepare an excited particle in a state with finite  
uncertainty in momentum. Around the particle, put a sherical detector that 
measures exactly (it's a thought experiment, ok :-) the momenta of massive
particles and the position of photons. Allow the excited particle to return
to ground state. Now, my detector tells me the momentum of the recoiling
particle. It also tells me the position of the photon. If conservation of
momentum holds, from the momentum of the recoiling particle and the the
momentum of the excited particle, I know the momentum of the photon to within
some finite uncertainty dp. But since dx = 0 for the photon, I have 
dp dx = 0. So, it seems that I have to either abandon conservation of energy
or Heisenberg's uncertainty principles.

What this seems to indicate is that conservation of momentum is true only
when you measure it to be true, ie, if you have not measured the momentum of 
all components of a system before and after an event, you cannot say anything 
about conservation of energy. This is in accord with my general understanding
of observation and measurement in QM. Or is there more to it?
--
########################## _`|'_ ##############################################
##  Warren G. Anderson     |o o| "... for its truth does not matter, and is  ##
##  Dept. of Physics       ( ^ )  unimaginable." -J. Ashbery, The New Spirit ##
##  University of Alberta  /\-/\      (anderson@fermi.phys.ualberta.ca)      ##
From: gfritz@sage.cc.purdue.edu ("Happy Fun Ball")
Newsgroups: sci.physics
Subject: Re: Time
Date: 9 Apr 92 00:31:02 GMT
Article-I.D.: mentor.44541
Organization: Purdue University Computing Center

In article <1992Apr8.071015.17512@ifi.uio.no> jarlo@ifi.uio.no (Jarl Magne Michael stensen) writes:
>
> Let me throw a rather large rock in the physical waters, hoping that it will
> create waves that perhaps can go all the way around the lake and back.
> I would want to ask all of you this wery simple (?) question: what is time?
[other stuff deleted]

  First, my disclaimer:  I am no expert on physics.  If you happen to think I
am wrong, then you are most likely right.  I'm just tossing an idea I read
about out onto the net to see what may become of it.  

  I personally like the theory that time is the forard-only path that denotes 
the increase of total entropy in the universe.  Non-stoppable and non-
reversible.  A simple answer (from my simple knowledge) for a simple question.

  You can't get a much more humble opinion than that. 

  Just my two pfennig worth.

Geoff
--
 ==============================================================================
 || "Maybe its imaginary, I'd like to know. ||            sage.cc.purdue.edu ||
 ||  What's the world coming to, and where  || gfritz @--(       or          ||
 ||    will it go?" -- Kirsty MacColl       ||            mn.ecn.purdue.edu  ||
 ==============================================================================
From: bhoughto@hopi.intel.com (Blair P. Houghton)
Newsgroups: sci.physics
Subject: Re: van de Graaff generators
Date: 13 Apr 92 23:35:39 GMT
Organization: Intel Corp, Chandler, AZ

In article <1992Apr10.085039.10688@dxcern.cern.ch> jeroen@dxcern.cern.ch (Jeroen Belleman) writes:
>Can anyone suggest a method to measure the output voltage? I do not
>think suitable probes exist.

There isn't really an "output voltage."  The potential on
the sphere is a function of the charge it holds and the
capacitance between it and the grounds around the room.

>So far, I get fat sparks from a polished 4cm diameter metal pipe over
>a little more than 10cm. The more diffuse sparks from the pipe's end
>easily exceed 50cm. You can make you own voltage estimates from that.

Drat.  I forgot the breakdown voltages for air.  The
potential at the time of the spark is of course just the
distance (cm) times the breakdown voltage (KV/cm).

As you can see, by varying the capacitance (a smooth surface
nearby; a sharp surface at a greater distance) your generator
can operate at different potentials.

If you integrate the charging current to get the charge you
can determine the capacitance.

You should put the entire apparatus in a large faraday cage
(perhaps you can wrap the room in foil :-)) and measure the
total displacement current to get the net charge--this also
gives you a roughly calculable basal capacitance.

				--Blair
				  "Watch where you point that thing..."
From: iavila@asgard.mty.itesm.mx (Isidro Avila Calderon)
Newsgroups: sci.physics
Subject: Curriculum of a B.S. in Physics in the U.S.
Date: 7 Apr 92 20:59:07 GMT


Hi!
I am interested of getting the curriculum that one student have to carry  
out to receive a B.S. in Physics (as a matter of fact, I dont know if B.S.  
in Physics is the correct expression). I am a student in Physics  
Engineering at Monterrey Tech (in MEXICO) and our curriculum is:
1st. Semester: Economy, French I, Mathematics for Engineering I (Calculus  
and Advanced Calculus), Chemistry (Organic and Inorganic), and Computation  
I (Integrated software: Word Processors, Databases, etc.).
2nd. Semester: Physics, Advanced Writing, French II, Mathematics for  
Engineering II (Calculus of Several Variables), Probability and  
Statistics.
3rd. Semester: Computation II (Introduction to Computer Science trough  
Pascal), Oral Communication, French III, Magnetism and Electricity,  
Mechanics, Differential Equations.
4th. Semester: Electric Circuits I, Optics, Partial Differential  
Equations, Linear Algebra, Statistics I, Developing of Business Spirit  
(Desarrollo de Emprendedores).
5th. Semester: Numerical Methods, Electric Circuits II, Modern Physics,  
Mathematical Methods, Complex Variable, Digital Image Processing.
6th. Semester: Electronic I, Theoretical Mechanics I, Modern Physics  
Laboratory, Optics Laboratory, World's Social and Cultural Values,  
Thermodynamics I, Holograms.
7th. Semester: Electronics II, Laboratory of Electronics I,  
Electromagnetical Theory, Theoretical Mechanics II, Social and Cultural  
Values in Mexico and Latinoamerica, Optical materials.
8th. Semester: Laboratory of Electronics II, Quantum Mechanics, Nuclear  
Physics, Professional Ethics, Optical Fibers, Topics of Physics I.
9th. Semester: Solid State, Development of Physics Proyects, Laboratory of  
Nuclear Physics (you may guess what happens if a student flunk an exam  
=-), Laboratory of Solid State, Total Quality Control, Lasers, Topics of  
Physics II.

And that's all folks: you get the Physics Engineer grade. Is this  
competitive? do we need a more indeep background? is it ok?
Actually -and if you have and average grade of B- you can take five  
courses more: Computers Architecture I, Digital Circuits, Microprocessors  
I and II, and Computers Architecture II). I will appreciate all of the  
responses, and -as always- if there is interest I will summarize. BTW, I  
am in my third semester =-).
Thanks:

Isidro Gerardo Avila-Calderon
--
iavila@asgard.mty.itesm.mx
Newsgroups: sci.physics
From: anderson@fermi.phys.ualberta.ca (Warren G. Anderson)
Subject: Re: Time
Organization: University Of Alberta, Edmonton Canada
Date: Wed, 8 Apr 1992 23:07:52 GMT

In article <1992Apr8.071015.17512@ifi.uio.no> jarlo@ifi.uio.no (Jarl Magne  
Michael stensen) writes:
> I would want to ask all of you this wery simple (?) question: what is time?

I'm not sure whether you realize this, but you are asking one of the biggest
questions in physics these days. Answering this satisfactorily would
lead (it is hoped) to understanding many of the unresolved issues in
quantizing gravity.
 
> Let me first try to recap the basic knowledge and ideas in physics today 
> about this subject. 
> 
> First of all, time is not absolute. At least this is what SR and GR states. 
> There is no absolute past and present, or absolute clock ticking somewhere in
> the heavens.
> Newton assumed this to be correct, after all muons and other strange beasts
> did not run around with big signs on them in his time either. But today we
> safely (?) assume that there is no absolute time.

It depends what you mean by absolute time. If we define spatial 3-surfaces
in the universe to be at constant time if they are homogeneous and isotropic
(which is standard in classical cosmology) then one can define a preferred
universal time. This is because the cosmic background radiation essentially
gives us a preferred frame.
 
> Time is closely related to the curvature of space and thus is a geometrical
> object. We know that the picture of the slowing of relative time in a strong
> gravitational well relates to the "dip" in space at the point. (In pictures)

This is true, but I think it does not address the point properly. Specifically,
the entire 4-D space-time bends when matter/energy is present. Thus, time
*and* space are altered. The real question (in my opinion) is why is one
of these 4 dimensions, time, singled out by other dynamical laws (as expressed
in the metric signature).
  
> Is it impossible that time could NOT be continous?

It would require a drastic change in our understanding of physics 
(especially quantum mechanics). I believe that a discretized time would
not allow for a discrete energy spectrum under that theory. Since we have
observed discrete energy spectra, there is certainly a large price to pay
for postulating discrete time.
 
--
########################## _`|'_ ##############################################
##  Warren G. Anderson     |o o| "... for its truth does not matter, and is  ##
##  Dept. of Physics       ( ^ )  unimaginable." -J. Ashbery, The New Spirit ##
##  University of Alberta  /\-/\      (anderson@fermi.phys.ualberta.ca)      ##
From: aephraim@physics (Aephraim Steinberg)
Newsgroups: sci.physics
Subject: Re: What is not being conserved?
Date: 10 Apr 1992 17:06:07 GMT
Organization: University of California, Berkeley
NNTP-Posting-Host: physics.berkeley.edu

In article <1992Apr9.213832.1911@hellgate.utah.edu> tolman%asylum.utah.edu@cs.utah.edu (Kenneth Tolman) writes:
>   In QM there is a probability that a photon will end up "hitting" a
>certain spot.  If there is only one photon, and it has a nondetermined
>end point, then some quantity is not being conserved.  Consider if I threw
>a ball, and then it appeared randomly.  How can there be equal and opposite
>reaction unless it is going to a specific place?
>
>   Obviously I have something wrong.  Does a photon have absolutely zero

No you haven't; it's quite a good question.

>momentum?  I thought that the idea behind solar sailing was to take 
>advantage of incredibly small momentums.
>
>  The other possibility is that it retroactively changes the transmitter.
>This seems pretty dubious.

In exactly the same way that a lot of quantum mechanics (viz. EPR) seems
pretty dubious.  ``Apocryphal yet true,'' as an old English teacher of
mine liked to say.  The simplest example for what you ask is an atom which
spontaneously decays, emitting one photon.  The photon is emitted over
a broad range of angles, e.g. in a characteristic ``dumbell'' dipole
radiation pattern.  The atom recoils, and its momentum is equally un-
certain, although the sum of the atomic and optical momenta is equal to
zero (in the rest frame of the initial, excited atom).  When a ``collapse''
occurs (or doesn't, I don't want to get into metaphysics in front of the
readers of this newsgroup any more) what is selected out is a state of
the entire atom+photon system, so if the photon is found to have gone off
in the +x direction, the atom will be found to have recoiled in the -x
direction, conserving momentum.  

aephraim

-- 
Aephraim M. Steinberg                    | "WHY must I treat the measuring
UCB Physics                              | device classically??  What will
aephraim@garnet.berkeley.edu             | happen to me if I don't??"
                                         |       -- Eugene Wigner
From: DOCTORJ@SLACVM.SLAC.STANFORD.EDU (Jon J Thaler)
Newsgroups: sci.physics
Subject: Re: SSC magnets - how?
Date: 7 Apr 92 18:25:07 GMT
Organization: Stanford Linear Accelerator Center

In article <8400007@trsvax>, pauls@trsvax.tandy.com says:

> AnotherSSC question:

People at FNAL and SSC can answer better, but here's some of the answer.

> 1) How many magnets are used?

About 10,000 dipole magnets.  I think there are also about 5000 others
(quadrupoles, etc).

> 2) In relative terms, how do they compare to other magnets in use today?

I *think* that they only extend previous magnet technology in their size.
The big issue in SSC magnet design has been field uniformity, but I don't
really know the present status.

> 3) What is MBTF of a magnet today (FermiLab)?

Don't know.  I think about 1/month (FNAL has 1000 superconducting magnets).

> 4) How many 'up days' (up hours??) does the average collider have today?

The rule of thumb is to assume 30% operating efficiency.  This is supposed
to accounts for all data loss, whether the accelerator's or experimenter's
fault. I don't know what recent FNAL experience has been, but at CERN (LEP)
it seems to work OK.

> 5) If a SSC magnet goes fubar, is the whole thing down?

If a ring magnet goes down, the accelerator is down for the few hours it
takes to replace it.
From: pk03+@andrew.cmu.edu (Paul Karol)
Newsgroups: sci.physics
Subject: Re: Physicists against evil
Date: 6 Apr 92 09:11:05 GMT
Organization: Chemistry, Carnegie Mellon, Pittsburgh, PA

Concerning a mathematical physicist 'against evil in all its forms'...

perhaps a mathematical physicist is exactly the correct person to
address this request to....Please define 'evil'.  Thank you.

Paul J. Karol
Experimental Nuclear Chemist