HDTenEightyP/NetNews huggingface dataset:
From: gross@maxwell.ucsc.edu (Mike Gross)
Newsgroups: sci.physics
Subject: Re: infinite universe
Date: 4 Jan 1993 19:31:08 GMT
Organization: University of California, Santa Cruz
NNTP-Posting-Host: maxwell.ucsc.edu

In <1993Jan4.184245.28970@novell.com> dseeman@novell.com (Daniel Seeman) writes:

>In article <1993Jan4.184114.151@vms.huji.ac.il> tabitha@vms.huji.ac.il writes:
>>Another question from a non-physicist.
>>
>>I frequently read that cosmologists debate whether the
>>universe has infinite size.  If the Big Bang started
>>at a definite time in the past, and has since expanded
>>at a finite speed, how can it be infinite?  What am
>>I missing?
>>

>On a philosophical level, what is the meaning of a Universe with a finite
>size?  What is happening at the boundary between that which is the Universe and
>that which is not?  And, what would happen if I stepped into that region which
>was defined as the "Non-Universe?"

>On this very non-rigourous (even symplistic) level, there can be no boundary to
>the Universe. Any "region" found outside the Universe would automatically
>become part of our Universe (which would have just expanded to include the
>"region" you were interested in).  I belive this provides a qualitative descript
>ion of the "Infinite Universe."

>dks.

Sorry, there is a hole in your argument. You have assumed that finite volume
implies the existence of a boundary. This is certainly true in Euclidean
geometry, but General Relativity is based upon more general spaces. The
cannonical counterexample is the surface of a sphere (or the Earth, if you
like). Despite the beliefs of the king of Portugal during the 15th century,
you can wander around anywhere you like on the surface of the Earth and never
find its edge. Yet, no one would argue that the Earth is infinite in size.

To answer the original poster's question, what cosmologists mean by an
"infinite" universe is that the universe will keep growing forever. Another
way to say this is that the universe has infinite four-dimensional volume
in spaceTIME. A finite universe means that at some point, the Hubble expansion
will halt and the universe will recontract. In four dimensions, the universe
will then have a finite volume. Of course, the three dimensional spatial
volume is finite at any finite time, as the original poster noticed.

Mike Gross
Physics Board
Univ of California                 GO SLUGS!!!!
Santa Cruz, CA 95064
gross@lick.ucsc.edu

Newsgroups: sci.physics
From: polowin@chem.queensu.ca (Joel Polowin)
Subject: Re: TIME HAS INERTIA       ABIAN replies to  KEITH THOMPSON
Organization: Dept. of Chemistry, Queen's University
Date: Mon, 4 Jan 1993 17:09:09 GMT

In article <1992Dec31.151458.21713@telesoft.com> kst@telesoft.com (Keith Thompson @pulsar) writes:

>My problem with Dr. Abian's theory is that it can explain anything, and
>therefore it explains nothing.  I've asked Dr. Abian to present one or
>more of the following:
>
>1. A potential observation, actual or imaginary, possible or
>   impossible, which could *not* be explained by, or which would
>   contradict, his theory.  Without this, I assert that his theory has
>   no predictive power.  It doesn't truly explain observations; at best,
>   it merely re-states them in different (and less rigorous) terms.

Abian has given several consequences of his theory which contradict
experimental observation.  He has stated that subatomic particles are
unstable inversely proportional to how "big" they are.  He has stated
that all of the interactions which currently are thought to vary as
1/r^2 really vary as 1/r^3.  He has stated that concentrated sulfuric
acid releases heat on mixing with water in order to maintain the status
quo of its concentration by evaporating the water away -- even though
conc. sulfuric readily absorbs water vapour from the air.

One doesn't win any Nobel prizes for theories that contradict piles and
piles of experimental data.

Joel Polowin
polowin@silicon.chem.queensu.ca, polowin@chem.queensu.ca,
polowinj@qucdn.queensu.ca
Newsgroups: sci.physics
From: atems@igor.physics.wayne.edu (Dale Atems)
Subject: Quantum Collapse and Bell's Inequality
Organization: Wayne State University, Detroit, MI
Date: Tue, 12 Jan 1993 08:05:12 GMT

As a followup to my earlier post:
 
Paul, I think the crux of any disagreement between us is whether you need
to invoke quantum collapse to predict the correlations that violate Bell's
inequality. This is *definitely* untrue for the spin-1/2 experiment I
described. The probability densities (space part of the wave function) at
each site are irrelevant in that case, to get the correlations one
makes use only of the spin part. I suspect the same is true for the
photon/polarization experiment as well, but I can't derive the probability
for joint detection offhand. Maybe later when I have time, or someone else
can supply the derivation.
 
The question of collapse of the spatial part of the wave function
only enters when the particle is actually detected (located in space).
Between polarizer and detector one has a linearly polarized wave
at each site. This is from wave optics and Maxwell's equations. In the
quantum interpretation the wave at each site contains information about
*both* photons. Until detection both photons are "spread out" over the
entire space occupied by the wave.

Yes, the detection event is problematic. But you don't need to consider
it at all to predict the measured correlations.

------
Dale Atems
Wayne State University, Detroit, MI
Department of Physics and Astronomy
atems@igor.physics.wayne.edu
Xref: sparky sci.physics:22369 news.groups:25240 sci.misc:1983
From: allenk@ugcs.caltech.edu (Allen Knutson)
Newsgroups: sci.physics,news.groups,sci.misc
Subject: Re: sci.physics.research: proposed panel of moderators
Date: 9 Jan 1993 06:06:23 GMT
Organization: California Institute of Technology, Pasadena
NNTP-Posting-Host: torment.ugcs.caltech.edu

markc@smsc.sony.com (Mark Corscadden) writes:

>Sci.math.research has no
>elementary discussion in it and it's a good enough group, if somewhat dry
>and low volume.  Is that really what is wanted for sci.physics.research,
>though?  So far it doesn't seem that way.  So far it seems like most
>people envision sci.physics.research being a lot more open and lively
>than sci.math.research.

I suspect that if sci.physics.research isn't the waste of quite so much
time that sci.physics is, it will be higher-volume than sci.math.research.
I think this because hep-th, the high-energy physics (theoretical)
mailing list has vastly more entries and subscribers than the algebraic
geometry or category theory mailing lists. So apparently there are more
physicists hip to Internet things.				Allen K.
From: leffler@physics.ubc.ca (Steve Leffler )
Newsgroups: sci.physics
Subject: Re: *.research request: limit number of articles per day
Date: 11 Jan 1993 21:16:51 GMT
Organization: The University of British Columbia
Distribution: world
NNTP-Posting-Host: physics.ubc.ca

rabson@oxford.ac.uk (David Rabson) writes:

>I should like to suggest that the moderated, research-oriented newsgroup
>should have a limit on the number of articles posted each day.  Twelve seems
>like a good number; it can be raised later if the moderators deem it
>helpful.

   I disagree.  I think that moderation of the group alone is already a 
sufficient restriction on postings, in that few people will be able to 
produce "too many" postings of high enough quality to pass moderation in one
day.  Anyone who can, should be able to.

				     ---Steven Leffler
					leffler@physics.ubc.ca
Organization: University of Illinois at Chicago
Date: Tue, 12 Jan 1993 11:15:28 CST
From: <U16072@uicvm.uic.edu>
Newsgroups: sci.physics
Subject: Re: knots and stat.mech.
 <1993Jan9.032758.29783@murdoch.acc.Virginia.EDU>
 <1ilhod$d4r@agate.berkeley.edu> <1993Jan11.210616.12263@galois.mit.edu>

In article <1993Jan11.210616.12263@galois.mit.edu>, jbaez@riesz.mit.edu (John C.
Baez) says:
>Vijanathi Chari and Andrew Pressley are writing a very good book on
>quantum groups, but it'll be a while before this gets published.

If it is not yet published , how can you (j. Baez) be sure it's a very
good book?

Thaddeus Olczyk
Newsgroups: sci.physics
From: pratt@Sunburn.Stanford.EDU (Vaughan R. Pratt)
Subject: Re: sci.physics.research: research-level only?
Organization: Computer Science Department,  Stanford University.
Date: Sat, 9 Jan 1993 16:30:55 GMT

In article <24790@galaxy.ucr.edu> baez@guitar.ucr.edu (john baez) writes:
>
>I too think that sci.physics.moderated would be a better name for what
>I'm after, but somehow when I came back from Christmas break sci.physics.research
>is what it was called.

Now that the moderators have stated their platforms, the prospect of
simply making sci.physics into a moderated group seems a whole lot less
threatening than it did at first.

A straw poll: taking the promised platforms at their face value, just
how many people here would feel that their rights were being
unacceptably trampled if sci.physics was simply turned into a moderated
group?

No sense giving up a nice monicker like sci.physics if it turns out
that this will benefit only a miniscule minority.
-- 
Vaughan Pratt				There's safety in certain numbers.
Xref: sparky sci.physics:22567 rec.arts.startrek.tech:7384
From: max@west.darkside.com (Erik Max Francis)
Newsgroups: sci.physics,rec.arts.startrek.tech
Subject: Re: Accellerating Spaceship (yet another bird in a plane)
Date: 12 Jan 93 08:37:44 GMT
Organization: The Dark Side of the Moon +1 408 245 SPAM

gunnarh@dhhalden.no (GUNNAR HORRIGMO) writes:

> But what if you had a chunk of negative mass and positive charge?

Same thing that would happen if you had a positive mass and a negative 
charge floating around . . . which we have in our Universe quite a bit.


  ____  Erik Max Francis -- ..!apple!uuwest!max -- max@west.darkside.com   __
  \  /  1070 Oakmont Dr. #1  San Jose, CA  95117  37 20 N 121 53 W  ACGT  /  \
   \/   Like strategic interstellar conquest games?  Ask about UNIVERSE!  \__/
        Omnia quia sunt, lumina sunt.   All things that are, are lights.
From: edremy@leland.Stanford.EDU (eric remy)
Subject: Constrained minimization
Summary: References
Organization: DSG, Stanford University, CA 94305, USA
Date: Tue, 12 Jan 93 21:48:15 GMT


Thanks to all those who responded to my request for a decent
introduction to constrained minimization.  The references which are
most useful:

Fletcher, _Practical Methods of Optimization_
Murray and Wright _Practical Optimization_
Scales, _Linear and Nonlinear Optimization_
Gill and Murray, _Numerical Methods for Constrained Optimization_

Numerical Recipes was mentioned several times, but only has code for
unconstrained optimizations, outside of some stuff on linear
programming. (Not useful, my problem has non-linear constraints.)

If anyone's curious, I'm currently using a method based on molecular
dynamics with constraints, but this is in general too slow to
converge. 

Thanks again for your help.
-- 
Eric R.      edremy@d31ha0.Stanford.EDU       Department of Chemistry
                        -1/2\nabla^2\psi_{T-72}
Newsgroups: sci.physics
From: sarfatti@well.sf.ca.us (Jack Sarfatti)
Subject: errata: re: sci.physics.research
Organization: Whole Earth 'Lectronic Link
Date: Sat, 9 Jan 1993 19:34:56 GMT


I meant to write "Gauge invariance in theory of superfluid helium" for
dissertation title.
Newsgroups: sci.physics
From: Leigh Palmer <palmer@sfu.ca>
Subject: Re: sci.physics.research: Are there important unresolved issues?
X-Xxmessage-Id: <A775B2C710011C1B@rs13-annex3.sfu.ca>
X-Xxdate: Sun, 10 Jan 93 19:02:31 GMT
Organization: Simon Fraser University
X-Useragent: Nuntius v1.1.1d16
Date: Sun, 10 Jan 1993 19:00:54 GMT

In article <MATT.93Jan10010325@physics2.berkeley.edu> Matt Austern,
matt@physics2.berkeley.edu writes:

>The purpose of this article is exactly what the subject line says: I'm
>trying to find out if there are any issues that haven't been resolved
>yet that people think are important.  (I think it's best that we do
>this before the vote, not after...)

OK, folks. I've kept out of this up to now, so I think I'm owed my two
cents worth. I saw a comment from a contributor whose name I have
fopgotten which, I believe, was meant to demonstrate what a fine
scholarly connoiseur he or she was. This person proudly disclosed the
contents of his or her killfile, revealing clearly to me that he or she
is an ignorant bigot. (No, my name was not listed as being in that
particular killfile, but I would have considered it not dishonorable to
have been in it, given at least one of the names that was.)

I have said nothing about the credentials of the gentlemen who have
volunteered to moderate the proposed group; indeed I approve of them all
(from what I know) and I suppose any one of them will be a possible route
into the group. I did notice that only one of the four has an advanced
degree in physics, an oddity which, I suspect, is unparalleled on
editorial boards of the print medium. I think that is an admirable
departure from tradition, given the publication "clubs" which we all know
exist in rags like PRL.

I'd like to see one more credential, however, before I lend my
unquestioning support to these estimable gentlemen. I'd like each to
publish his killfile (if he has one). While I will not volunteer to
moderate (I'm an immoderate type by nature), I will tell you that I do
not have a killfile, but I read selectively, choosing articles from a
menu like a table of contents, in a newsreader which runs on a Macintosh.

I feel that revelation of these killfiles cannot diminish my respect for
any of the gentlemen proposed (why are there no ladies?) and that
self-examination of them may help at least some among them to become
better moderators.

Collegially,

Leigh

(I just figured out why there are no ladies. Ladies are too smart to mess
in here. I note that, with one ephemeral exception, ladies don't play ice
hockey, either. If the metaphor fits,...)
Newsgroups: sci.physics,news.groups,sci.misc,alt.sci.physics.new-theories
From: merritt@macro.bu.edu (Sean Merritt)
Newsgroups: sci.physics
Subject: Re: sci.physics.research: Are there important unresolved issues?
Date: 12 Jan 93 15:28:55 GMT
	<1993Jan11.223445.13105@galois.mit.edu>
Organization: Boston University Physics Department
In-reply-to: jbaez@riesz.mit.edu's message of 11 Jan 93 22:34:45 GMT


#In article <1993Jan11.223445.13105@galois.mit.edu> jbaez@riesz.mit.edu (John C. Baez) writes:




   Sean Merritt writes:

   >As I stated before I object to one memeber of the panel. Now I find that
   >after the discussion I also don't have much confidence in Baez to
   >perform as a "filter" if articles in sum are to be considered as
   >ensembles of indistinguishable particles. Nevertheless I feel that he
   >and Dale may have some "constructive ineterference" efffect and 
   >all my objections may be for nought.(see below)

 #  Could you provide a more specific and less metaphorical explanation of
 #  why you no longer have confidence in my abilities as a filter?
 #  Certainly if a majority of people think I'm being unduly harsh on
 #  articles about interpretation of QM, I will gladly recant (as I mentioned).

 Your analogy, and I must paraphrase, was that you would bow out if there
 was a dispute over an article, then you proceded to to say something
 about electrons and indistiguishable particles. If you can't differentiate
 you will not be a good filter. As I said above though it is much more
 important that the criteria(for acceptance/rejection of articles) 
 are posted here before we vote.

 I have looked at "moderated groups" and they are mostly moderated by
 a single person. My software doesn't show a "Approved by:" line.
 It should be included somehow. This will allow the reader to 
 "track" the performance of each moderator. If a single moderator
 posts artciles that are of a low quality (in the opinion of
 the reader) than she may place that moderator in a kill file.
 Instead of undiscriminated signal like we have in sci.physics,
 we will have 4 distinct signals with different thresholds.
 If one channel becomes too noisy the reader has the option of
 turning it off.

 I would even say we let the moderators "filter" themselves,
 rather than have another moderator "approve" thier articles.
 That way the moderator's own posts will either increase or
 decrease the S/N ratio of that channel.

 -sjm


--
Sean J. Merritt		         | "Every revolt is a cry of innocence    
Dept of Physics Boston University|  and an appeal to the essence of being."
merritt@macro.bu.edu             | Albert Camus, The Rebel
Newsgroups: sci.physics
From: sschaff@roc.SLAC.Stanford.EDU (Stephen F. Schaffner)
Subject: Re: Okay, it's not the inverse sprinkler problem...
Organization: Stanford Linear Accelerator Center
Distribution: sci
Date: Tue, 12 Jan 1993 18:28:12 GMT

In article <1993Jan12.160756.14894@linus.mitre.org>, m14494@mwvm.mitre.org (Mike White) writes:
|> Mark Schnitzius writes:
|> > At first it seems that "hitting the clutch" would be the
|> > proper answer, so your car would provide the least resistance
|> > to the oncoming car.  But consider -- shouldn't your goal
|> > be to reduce the sudden acceleration that you will be 
|> > experiencing?  If that's the case, then maybe hitting the
|> > brake would be the correct answer.
|> 
|> It might be, if your car was incompressable.  In fact, most of
|> your injuries would probably stem from deformation of the car, and
|> subquent crush injuries and rupture of the gas tank and fire/explosion.
|> You did't give enough information to answer the question: is the car in
|> question a Volvo or a Pinto?

	Why are real-world problems always so complicated?  I doubt crush 
injuries would be that big a risk in a rear-end collision, but the 
gas tank is worrisome; how much gas is in the tank?  On the other hand, 
hitting the clutch increases your chances of being forced into oncoming 
traffic and being hit again.  I think the "official" answer (i.e. I saw 
it in some driving manual somewhere, and we all know how reliable books 
are) is to brake.  
	 Come to think of it, I drive an automatic, so I'll probably never 
get to try the experiment.  How disappointing.

-- 
Steve Schaffner        sschaff@unixhub.slac.stanford.edu
	The opinions expressed may be mine, and may not be those of SLAC, 
Stanford University, or the DOE.
From: dseeman@novell.com (Daniel Seeman)
Newsgroups: sci.physics
Subject: Re: infinite universe
Date: 11 Jan 93 16:30:56 GMT
Organization: Novell Inc., San Jose, Califonia

In article <19409@mindlink.bc.ca> Terry_Martin@mindlink.bc.ca (Terry Martin) writes:
>Questions by a non-scientist;
>
>a) Can matter and space occupy the same volume simultaneously?
>b) We define the universe in terms of General Relativity and Quantuum
>Mechanics. I understand that these generalized terms describe the observable
>universe on cosmological and sub-atomic levels reasonably well, but are
>incompatible when combined in that they result in a singularity.
>
>This implies to me that we can have a universe in which space-time can exist
>in the absence of matter, but not vise versa; matter can not exist in the
>absence of space-time without arriving at the dreaded singularity.
>
>If this is true, and we can have a universe which includes space-time but not
>matter, which by definition would also exclude gravity and quantuum
>mechanical effects, in what terms would the universe be described? (I assume
>it would contain energy).

If it contains energy, it probably contains matter.

dks.
Newsgroups: sci.physics
From: schnitzi@cs.ucf.edu (Mark Schnitzius)
Subject: Okay, it's not the inverse sprinkler problem...
Organization: University of Central Florida
Distribution: sci
Date: Tue, 12 Jan 1993 14:39:44 GMT

I was discussing this problem with the guy I carpool with
the other day...  It seems to be one of those physics
problems that can be argued either way.

Suppose you are stopped in your car at a stop light.  In
your rearview you see an approaching car that is moving
too fast to stop -- it is going to plow into you.  You
have just time enough to do one of two things -- apply
the brake, or apply the clutch.  From a personal survival
standpoint, which choice would be in your best interest?

At first it seems that "hitting the clutch" would be the
proper answer, so your car would provide the least resistance
to the oncoming car.  But consider -- shouldn't your goal
be to reduce the sudden acceleration that you will be 
experiencing?  If that's the case, then maybe hitting the
brake would be the correct answer.

Thoughts, anyone?


Mark Schnitzius
schnitzi@eola.cs.ucf.edu
University of Central Florida
From: ig25@fg70.rz.uni-karlsruhe.de (Thomas Koenig)
Newsgroups: sci.physics
Subject: Different kinds of fluids (was: bird in plane)
Date: 8 Jan 1993 09:57:07 GMT
Organization: University of Karlsruhe, Germany
Reply-To: ig25@rz.uni-karlsruhe.de
NNTP-Posting-Host: fg70.rz.uni-karlsruhe.de

In article <1992Dec7.155530.9637@newshost.lanl.gov> u108502@beta.lanl.gov (Andrew Poutiatine) writes:

>Air is in act a fluid,

Yes.

>and at atmospheric conditions it behaves very similarly to an
>ideal fluid.

What's that?

>RW Fox and AT McDonald define a fluid in the book _Introduction
>to Fluid Mechanics_ as "a substance that deforms continuously under the 
>application of a shear (tangential) stress no matter hOW small the shear stress
>may be." 

Again, correct.

> In fact that is the definition of a Newtonian Fluid.

No.  A Newtonian fluid has the additional property that shear stress and
rate of deformation are proportional.  The rate of proportionality is
the viscosity.  Many other fluids show more complicated behaviour,
polymer melts are a classical example.  Often, fluids show viscoelastic
behaviour; if you choose your timescale short enough, you get elasticity;
if you choose it long enough, you get viscous behaviour.  Remember the
bouncing putty?

(As an aside, it is generally assumed that there is no such thing as a
perfect Newtionian fluid, but you'd have to get down to about 10^-10 s
to find viscoelastic properties in water, so it does not really
matter...)
-- 
Thomas Koenig, ig25@rz.uni-karlsruhe.de, ig25@dkauni2.bitnet
The joy of engineering is to find a straight line on a double logarithmic
diagram.
From: bhoughto@sedona.intel.com (Blair P. Houghton)
Newsgroups: sci.physics
Subject: Re: Could Ben Franklin have guessed which end was '-'?
Date: 5 Jan 1993 21:35:48 GMT
Organization: Intel Corp., Chandler, Arizona
NNTP-Posting-Host: stealth.intel.com

In article <C0Cq53.MC7@efi.com> chrisp@efi.com (Chris Phoenix) writes:
>I often hear that Ben Franklin made the wrong guess about which side
>of a battery had an excess of electrons, but that there was no way for
>him to tell the difference.

He knew where the electrons were only so far as he knew
what elektron was[*].  Rutherford hadn't yet invented
ionizable atoms.

About the only way he could have known that there was an
excess of electrons building up in one part of an object
would have been to measure the change in mass, if he
believed that electrons had mass.

The question then becomes could he have made such a measurement?

				--Blair
				  "Holy Caloric, Batman!"

[*]  elektron [Gr. amber]: the negative end of the triboelectric
scale; where the electrons (and the prehistoric flies) gather when
amber is rubbed against most other materials.