HDTenEightyP/NetNews huggingface dataset:
Newsgroups: sci.physics
Subject: Re: Some physics questions
From: mcirvin@husc8.harvard.edu (Mcirvin)
Date: 5 Nov 92 18:01:48 GMT

>jac@ds8.scri.fsu.edu (Jim Carr) writes:
>The annihilation would create photons which would have some
>contribution to the stress-energy tensor, so this wouldn't really
>work in principle either.  Gravitational waves (defined as small
>perturbations to a background metric) propagate at the speed of
>light, however.  This is a good an answer as I can give to the
>original question (please, let's not get into the "speed-of-gravity" 
>war again!)

The question asked what would happen if the sun disappeared, to
which the only good answer is Feynman's "*How* are you going to
make it disappear?"  The answer certainly depends on the details.
Within the context of current physics, it *can't* just blink out of
existence, so asking what would happen in that case, given GR,
is a question with no answer.
-- 
Matt McIrvin
From: frenkel@stcst1.mrl.uiuc.edu (David Frenkel)
Newsgroups: sci.physics
Subject: Re: Solid-state doesn't use QED! (Was Re: Particle Research)
Date: 6 Nov 92 15:56:32 GMT
Article-I.D.: news.BxAxMB.LCM
Organization: Dept of Physics, Univ of Illinois, Urbana

In article <BxA2GC.6yE@wsrcc.com> alison@wsrcc.com (Alison Chaiken) writes:
>music@erich.triumf.ca (FRED W. BACH) writes:

>As far as the theory of the electron goes, QED has had
>no impact on solid-state physics whatsoever.
>Solid-state physics doesn't really even use the full Dirac equation,
>except that we are interested in the magnetic moment of the electron,
>which the equation explains qualitatively.

   Dirac equation has been used in band structure calculations
   of heavier elements. It is true, however, that most of
   Solid State physics can be done without it.

>Having said all that, the theories of broken symmetry and elementary
>excitations (Goldstone bosons) in solid-state physics have been heavily
>influenced by particle theories.  Here solid-state is using the
>_concepts_ of field theory, not the results!

   Solid State physics uses _techniques_ originally developed
   for QED all the time.
   Feynman diagrams are a standard tool used in everyday work.
   Path integrals, also developed by Feynman for QED, have been 
   used in a number of areas of solid state physics.
   And do not forget the renormalization group theory of phase
   transitions -- its origins are as much in field theory as they
   are outside of it.
   I really would not underestimate the impact of field theory on
   condensed matter.
   I will go as far as saying that solid state physics would have been
   much less today without those techniques  -- it is a perfect
   illustration of the need support many kinds of basic research,
   not just the ones that `look useful'.

>My understanding is that
>particle theories have been in turn influenced by solid-state theories
>(e.g., non-perturbative field theories are greatly influenced by the
>BCS theory of superconductivity).

   True enough.

-- 
David Frenkel                        | e-mail:   frenkel@stcst1.mrl.uiuc.edu 
Department of Physics,               | 
University of Illinois at            |
Urbana-Champaign, Urbana, IL, USA    |
Newsgroups: sci.physics
From: u108502@beta.lanl.gov (Andrew Poutiatine)
Subject: Re: Do Balloons fly?
Organization: Los Alamos National Laboratory
Date: Mon, 9 Nov 1992 18:41:24 GMT

In article <1992Nov6.170202.17174@husc3.harvard.edu> mcrae@husc8.harvard.edu writes:
>In article <1992Nov6.152707.8015@newshost.lanl.gov>, u108502@beta.lanl.gov (Andrew Poutiatine) writes:
>> Secondly, although Andrew McRae's example is thought provoking, it is only
>> that, since if in a gravitational field you somehow removed the pressure
>> gradient, there would be nothing to hold the air in place, and it would
>> accelerate constantly, as would the balloon, in the direction of the gravity
>> vector.
>> You simply cannot hold air in its place without a pressure gradient in a grav-
>> itational field.
>
>That's why I wrote:
>
>>>                                         So consider a helium balloon in a
>>>closed room with constant (to a close-enough approximation) pressure
>                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>>throughout, so that the balloon's volume is independent of its position.
>
>If you can show that the approximation fails, I'd be fascinated. I only
>introduced it to avoid having to worry about the details of the balloon
>expanding as it rose -- in fact, I'm sure that replacing it by the
>assumption that "no matter where the balloon is in the room, it displaces
>air that weighs more than it does" allows the argument to go through
>unchanged.
>
>Of course, one should _expect_ that the balloon's behaviour could be
>explained both by considering the forces that act and by considering
>conservation of energy -- it always works that way! (I just think that in
>this case, the energy argument is a damn' sight simpler!)
>
>Andrew.
>
>-- 
>Andrew McRae                       Internet: mcrae@husc.harvard.edu
>                                     BITnet: mcrae@HUSC

If I understood the point of your first post, it was that in the absense of 
pressure differentials in the room, the balloon would still rise due to your
energy argument.  My point is that you cannot have the uniform pressure
with gravity, and with gravity and the resultant forces, the statistical
microscopic effects of which you wrote become paradoxical.

-AIP

Newsgroups: sci.physics
From: palmer@sfu.ca (Leigh Palmer)
Subject: Re: Compelling Mysteries (II)
Organization: Simon Fraser University
Date: Tue, 10 Nov 1992 20:30:37 GMT

In article <1992Nov10.151421.11274@murdoch.acc.Virginia.EDU>
crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass) writes asking us for
conundra.

How 'bout the question of particle-antiparticle asymmetry of the universe? I
realize that there is a clear majority position in the polls, but is that the
way we do science?

What are the gamma ray bursters? One of the arguments advanced by proponents of
orthodoxy on the first conundrum was that annihilation radiation was not seen
from intergalactic space. Could be we've started to see some? Could be we've
just started to look for it.

Leigh
From: frisinv@alleg.edu
Subject: Lecture on Maxwell's Equations
Organization: Allegheny College
Date: Tue, 10 Nov 1992 19:42:13 GMT

  As part of a project on creativity in math, I am giving a short lecture  
on Maxwell's equations to a group of college freshmen who have not had  
extensive math and physics (everyone has had calc 1 and highschool physics  
w/o calc). I can handle explaining the equations themselves in words IF I  
use the integral forms. However, I also want to show the derivation of E-M  
waves from them, a messy process. Does anyone have an idea or two on how  
to do this in a comprehensible way? The idea isn't to teach the class  
electomagnetic theory, just to give them a general idea of Maxwell's  
equations and why light is a form of E-M wave.

Email frisinv@alleg.edu with any ideas.

Vincent Frisina
--
Newsgroups: sci.physics
From: crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass)
Subject: Re: NEWS: Galileo Cleared of Heresy Charges by Vatican
Organization: University of Virginia
Date: Fri, 6 Nov 1992 18:40:51 GMT

In article <6203@tuegate.tue.nl> johan@blade.stack.urc.tue.nl (Johan Wevers) writes:
>sichase@csa1.lbl.gov (SCOTT I CHASE) writes:
>
>>I think that the Vatican statement is more general than you imply. The 
>>point is not that the Church now accepts that the world is Galilean. Rather,
>>it conceeds that physics is the right tool for understanding the physical
>>world, and that the Church should not get involved in deciding whether or 
>>not a particular cosmology is right or wrong.  
>
>So they won't resist against the inflation model were the big bang was
>created from an instable false vacuum, where no gods are needed any more
>for the creation of the universe?

      Please keep your particular religion out of science, it
      has no place there.  Since there can always be a time *before* you
      have any kind of false vacuum, bang or inflation, this discussion 
      simply *invites* consideration of initial conditions set up by 'gods'.

                           dale bass
-- 
C. R. Bass                                          crb7q@virginia.edu        
Department of Mechanical, 
     Aerospace and Nuclear Engineering
University of Virginia                              (804) 924-7926
Newsgroups: sci.physics
From: jbaez@riesz.mit.edu (John C. Baez)
Subject: Re: Ferromagnetism (was: Compelling Mysteries)
Organization: MIT Department of Mathematics, Cambridge, MA
Date: Wed, 11 Nov 92 20:45:19 GMT

In article <BxJFGI.4D5@wsrcc.com> alison@wsrcc.com (Alison Chaiken) writes:

>The $0.05 answer: The fundamental underlying cause of conduction
>electron "itinerant" ferromagnetism is the Pauli exclusion principle.
>In some sense the exclusion principle causes a repulsive force between
>electrons of the same energy and spin.  (This is really an indirect
>manifestation of the Coulomb repulsion between like charges.)  The
>converse of the preceding statement is that if you have a low-density
>electron gas, there is an effective net force aligning the spins.

Hmm, now that we have solid state theorist talking we should ask some
questions.  I don't get this "converse" at all.  Are you saying that the
Pauli exclusion principle alone causes electron spins to tend to line up
in a dilute electron gas?  That seems mighty weird.  Or do the magnetic
moments of the electrons also play a role?

>Thus, a large-lattice-constant metal will have a tendency towards
>ferromagnetism.

What's the lattice constant, and why does this give you a low-density
electron gas?

>This is especially true in a degenerate system
>because the high density of states at the Fermi level means a big
>energetic win for opening up an energy gap.  

Sorry, I don't get this either.

Feel free to answer as tersely or loquaciously as you like... I think
there are a bunch of us out here that are interested but not quite up to speed.


Newsgroups: sci.physics
From: jones@ils.nwu.edu
Subject: New Ph.D. Program
Organization: institute for the learning sciences
Date: Mon, 9 Nov 1992 20:25:08 GMT

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Newsgroups: sci.physics
From: crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass)
Subject: Re: Religion & Physics Don't Mix
Organization: University of Virginia
Date: Thu, 5 Nov 1992 17:33:52 GMT

In article <73753@hydra.gatech.EDU> cegtitd@prism.gatech.EDU (Tim Dodd) writes:
>
>+     As far as 'reality' goes, if you may define it as you wish,
>+     just don't expect everybody else to share the definition, especially
>+     outside of science.
>+
>
>If a concept is defined in such a manner that it cannot in principle
>ever be shown to pertain to a component of reality, that concept is by
>definition meaningless. 

     This seems to depend, to a great degree, on your definition of 
     'reality'.  You may well define it so that anything that is 
     not reality is meaningless.  If, however, you define it so that reality
     is equivalent to the domain of science,  things that are outside
     do not lack innate 'meaning.'  In fact, it is arguable that *any*
     concept of which one can conceive has 'meaning' simply in the conception,
     regardless of the nature of 'reality'.

                             dale bass
-- 
C. R. Bass                                           crb7q@virginia.edu
Department of Mechanical and Aerospace Engineering
University of Virginia
Charlottesville, Virginia                            (804) 924-7926
Newsgroups: sci.physics
From: sarfatti@well.sf.ca.us (Jack Sarfatti)
Subject: Typo correction in |a,b> eq.
Organization: Whole Earth 'Lectronic Link
Date: Thu, 12 Nov 1992 19:42:41 GMT


Erratum
Ramsay quotes me as writing:

||a,b>  = {|a,e,+>|b,e,+> + |a,e,->|b,e,->}/sqrt2
|
||a,b>' = {e^iphi|a,e,+>|b,e,+> + |b,e,->|a,o,+>}/sqrt2

If that is what I wrote- it is not what I intended - the correct equations
are:

||a,b>  = {|a,e,+>|b,e,+> + |a,o,->|b,o,->}/sqrt2
|
||a,b>' = {e^iphi|a,e,+>|b,e,+> + |b,o,->|a,o,+>}/sqrt2

with similar typographical corrections in any consequent equations
From: MRG3@psuvm.psu.edu
Newsgroups: sci.physics
Subject: Re: Error in NO FTL Signal Proofs exposed.
Date: 12 Nov 92 13:29:12 GMT
Organization: Penn State University

In article <BxJ3Fz.CKK@well.sf.ca.us>, sarfatti@well.sf.ca.us (Jack Sarfatti)
says:
>
>Trivial, but false, formal proof that quantum connection communication is
>impossible.
>
>Nonlocal joint probability that receiver photon b counted in + channel and
>twin transmitter photon counted in phi channel is
>
>p(b+|a,phi) = <a,b| |+><+| |phi><phi| |a,b>
>
.......
>1) |a,b> can have a parametric dependence on phi so that it is
>mathematically incorrect to use the completeness relation in isolation. So
>that it does not cancel out of the problem destroying the controllable
>nonlocal coherence effect.


For the case of the spin entangled system, Sarfatti is saying that the
initial conditions |a,b> of the spin system depend upon what the observer
at one side of an EPR type experiment cchooses to measure.
The effect of the measuring apparatus
on the system which produces the correlated photon system
still propogates at the speed of light or less.  Hence no effect could be
seen outside of the future light cone of the event "choose to measure phi".
Hence any effect of this sort is due to luminal or subluminal transmission
of information via interaction between one of the detectors and the
coorelated photon source.  I believe it was Paul Budnik who has pointed out
that these type of effects may still not be ruled out in the actual
Aspect experiments.  There are NOT an indication of superluminal
signaling capability.
-mike gallis
freelance physicist
(for hire?)
From: cegtitd@prism.gatech.EDU (Tim Dodd)
Newsgroups: sci.physics
Subject: Re: Religion & Physics Don't Mix
Date: 9 Nov 92 15:26:04 GMT
Organization: Georgia Institute of Technology

In article <BxB855.7Mq@unixhub.SLAC.Stanford.EDU| sschaff@roc.SLAC.Stanford.EDU (Stephen F. Schaffner) writes:
|In article <73878@hydra.gatech.EDU|, cegtitd@prism.gatech.EDU (Tim Dodd) writes:
|[on whether religious talk can be considered meaningful]
|
||| In order to judge whether a particular concept is meaningful, it is not enough
||| to ask if the concept exists.  Even asking the question makes it clear that
||| it does.  One must ask if the concept has any real referents.  If it
||| cannot be shown that such referents exist, then the concept is meaningless
||| as it does not refer to anything.
|
|It's not clear to me exactly what you mean by reality.  Religious believers in 
|general think that God is part of reality, just that he is not demostrable by 
|scientific means.  Is reality to be identified with physical reality?  In an 
|earlier post (which apparantly no longer exists -- is this an ironic gesture 
|on the part of Usenet?) you seemed to suggest that for a word or concept to be 
|meaningful, it had not only to refer to an element of reality, but had to refer 
|to an element that could (at least in principle) be detected.  Is this in fact 
|your position?

Yes.  If God were part of reality, then his existence would be demonstrable.
However, God is *defined* as being non-demonstrable.

|It seems pretty clear to me that the concept of meaning that you espouse is 
|itself meaningless under your own definition (meaning does not, after all, 
|refer to anything observable), and is in fact a philosophical rather than 
|a scientific statement.  

Au contraire:  I defined "meaning" in an earlier post.  It most certainly
refers to something real.

Tim
-- 
Tim Dodd, Research Scientist, Georgia Tech:  cegtitd@prism.gatech.edu
Newsgroups: sci.physics
From: phfrom@nyx.uni-konstanz.de (Hartmut Frommert)
Subject: Re: Gravitation & massless particles (was Re: Some physics questions)
Organization: Dept. of Physics, University of Constance
Date: Thu, 5 Nov 1992 10:16:19 GMT

radford@cs.toronto.edu (Radford Neal) writes:

>In article <11264@sun13.scri.fsu.edu> jac@ds8.scri.fsu.edu (Jim Carr) writes:

>> In principle, one could measure the change in gravity when a particle 
>> and anti-particle annihilate, but in practice ....


>Hmm... this seems wrong to me. Wouldn't the photons (or whatnot) that
>result from the annihilation still exert gravitational force?

Exactly what I stated in my prev post..
--
 Hartmut Frommert                 <phfrom@nyx.uni-konstanz.de>
 Dept of Physics, Univ of Constance, P.O.Box 55 60, D-W-7750 Konstanz, Germany
                                           -- Eat whale killers, not whales --
Newsgroups: sci.physics
From: jbaez@riesz.mit.edu (John C. Baez)
Subject: Re: NASA Coverup
Organization: MIT Department of Mathematics, Cambridge, MA
Date: Tue, 10 Nov 92 04:29:27 GMT

In article <11283@sun13.scri.fsu.edu> jac@ds8.scri.fsu.edu (Jim Carr) writes:

>I know plenty of people who saw the launch live, but most of them are 
>'gators' so it *is* possible that there is a massive conspiracy afoot. 
>As to the film, I saw the moon walk on live TV and can state that it 
>looks the same in later playbacks as it did then.  But then, I could 
>be part of the conspiracy too!  ;-) 

Let's admit it.  EVERYONE on sci.physics is part of the coverup, so
snarfy is just wasting his time posting here.

Newsgroups: sci.physics
From: crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass)
Subject: Re: Religion & Physics Don't Mix
Organization: University of Virginia
Date: Fri, 13 Nov 1992 18:01:57 GMT

In article <1dp3vgINN7n2@chnews.intel.com> bhoughto@sedona.intel.com (Blair P. Houghton) writes:

>Then I am utterly guilty of worshipping science; for I am
>an inveterate empiricist.

     Worship at will.  Do not confuse this with science.

     How is your inveterate 'empiricism' and worship thereof empirically
     based?
     
>I've read Whitman's (or was it Frost's) descriptions of the
>facets of the process of maturation in which one grows by
>learning to consider ideas from a multitude of sides
>without becoming unglued.  (This is not the same thing as

     A book is no place from which to get ones spirituality?
     Obviously, you get yours straight from God, he said dryly.

>tolerating fools, Corky.)  Einstein's beliefs seem

     I like the cute name, Blair buddy.  Reminds me of the 
     'debates' in second or third grade.  Is this the brand of
     withering logic that you use to undermine the religious
     beliefs of the flock using 'science'?  Good luck.

>strangely sociological, as though he were afraid that being
>both physically and spiritually revolutionary at the same
>time would be too much for his society, or at least very
>impolitic at a time when his stature was needed as much as
>his theories.  He joins with many here who think, "I want
>it to exist; I try to prove it exists; I cannot prove it
>doesn't exist; *therefore it can exist; therefore it
>exists as much as I want."  In the end the only reality is
>that God existed for Einstein to suit his needs for a God.
>God does not exist for me and I have no need for a god.

     A position you seem to sympathize with.  You want your religion
     to be able to disprove all other religions.  When you cannot
     do that, you seem to become agitated.  Unfortunately, you have
     inappropriately given your religion the name 'science', otherwise
     there would be no problem here. 

>[*] There is a fallacy in crossing this point.

     Nope, not from the viewpoint of science. Better yet, why don't
     you explain what the fallacy is?  Graphs and charts would be
     very helpful.

>>I figure the best thing is to ignore them.  Just like
>>I ignore street preachers.
>
>The worst thing is to ignore anyone, if you have nothing
>better to do.  The best thing about street preachers is
>their foundation is narrow so they're easy to tip over.
>Tripping them up impresses intelligent women, too ;-).

     Or makes you look silly and arrogant.  I hope you don't inappropriately
     use the imprimatur of science in such ridiculous pursuits.

                        dale bass
-- 
C. R. Bass                                          crb7q@virginia.edu        
Department of Mechanical, 
     Aerospace and Nuclear Engineering
University of Virginia                              (804) 924-7926
Newsgroups: sci.physics
From: hagerman@ece.cmu.edu (John Hagerman)
Subject: Re: History of AC vs DC Power
Organization: Carnegie Mellon University
Date: Wed, 11 Nov 1992 18:12:43 GMT

In article <1992Nov11.154425.8399@speedy.aero.org> steve@pepe.aero.org (Steve Sedlacek) writes:

> Why is our power system completely AC?

Simple answer:

(1) Efficient transmission requires high voltages, safe use requires
low voltages; transformers were by far the easiest and most efficient
way to convert.  (Wood is still used in their construction!)

(2) Tesla invented the induction motor: high efficiency and long life
implied money for the maker.  Westinghouse was the maker, and its size
allowed it to exert a large influence on the power industry.

- John
--
hagerman@ece.cmu.edu
From: rabson@oxford.ac.uk (David Rabson)
Newsgroups: sci.physics
Subject: preprints bulletin boards (babbage.sissa, xxx.lanl) dead?
Date: 13 Nov 92 11:56:06 GMT
Organization: Oxford University Computing Service, 13 Banbury Rd, Oxford, UK
Originator: rabson@black

We've been unable to send requests to cond_mat or hep at babbage.sissa.it
or at xxx.lanl.gov, nor have we received any abstracts in the last week.

Messages sent to these mail servers are returned with an error concerning
inability to fork, suggesting that the process table is full, yet people
_seem_ to be logged in to the system.  (Note that mail sent to Los Alamos
is forwarded to Babbage).

If anyone at Trieste or wherever babbage.sissa.it is located sees this,
could she please let us know when the service will be available again?

Many thanks,
David Rabson

Theoretical Physics, Oxford
Newsgroups: sci.physics