HDTenEightyP/NetNews huggingface dataset:
From: bweiner@ruhets.rutgers.edu (Benjamin Weiner)
Newsgroups: sci.physics
Subject: Re: The Future of Physics
Date: 22 Jul 92 19:44:12 GMT
Organization: Rutgers Univ., New Brunswick, N.J.

Philip Bond writes:
> Leigh Palmer writes:
>>  ...  Many who did not make it, indeed many who
>>did not even apply, or could not because of residential or financial
>>condition would love to be in your position. Abandon the spurious
>>motivation you express here implicitly and seize the wonderful
>>opportunity which you have been given.
>
>Since when is wanting a reasonable job a spurious motivation ? Having a decent
>job that is socially useful and pays OK ( "fairly reasonably" ) is a damn
>fine ambition in my view.

Good point - too much idealism can be dangerous.  I've tried an
extended period of unemployment, and it's not exactly spiritually
rewarding.  There's nothing wrong with thinking pragmatically about
your future prospects (I think the maxim should be "The lack of money
is the root of evil") - especially if you're a physics grad student,
or even any college student, given how dismal the job market's been
lately.

On the other hand, Leigh is very correct in saying, essentially,
that you (we) are lucky to have gotten this far.  Better to be an
unemployed physics PhD than an unemployed high school graduate - or
dropout.  The originator of this thread, the undergrad, should
consider many career decisions can be postponed, and at least in
physics we're lucky; the departments can pay you to go to school.

Ben

P.S.  Phil, are you _sure_ that working for Salomon Bros. is "socially
useful"?   ;)
From: gt3716a@prism.gatech.EDU (Josh 'I'd MUCH rather be diving' Freeman)
Newsgroups: sci.physics
Subject: Re: "What's New" July-24-1992
Date: 28 Jul 92 14:16:34 GMT
Organization: Georgia Institute of Technology

I would like Nasa to work with the Russian space agency and possibly merge
Mir (which means "peace" in Russian ) to freedom. It seems that it is more
logical to work together than to devote the resources of two nations that 
are struggling to overcome an economic morass. On sci.space there was talk
of a shuttle-Mir mission in a few years. If we can doch a shuttle to Mir, we
can dock a Freedom section. It seems logical to me. Any Comments?

"If pro is opposite con, 
Then Progress is opposite Congress." -- unbeknownst to me.

-- 
What Is your name?
What is your quest?
What is the DeBroglie wavelength of an unladen swallow?
Joshua Kimbrell Freeman, gt3716a@prism.gatech.edu
Newsgroups: sci.physics
From: jbaez@riesz.mit.edu (John C. Baez)
Subject: Re: Quantum Cosmological Boundaries and Determinisim?
Organization: MIT Department of Mathematics, Cambridge, MA
Date: Thu, 23 Jul 92 15:38:11 GMT

In article <mcirvin.711851892@husc8> mcirvin@husc8.harvard.edu (Mcirvin) writes:

>Someone recently mentioned that in 
>quantum cosmology, though, there might be such a thing as a truly mixed
>state-- that the universe might be describable only by a density matrix,
>not a single state vector or wave function.  Is this related to the idea
>of degrees of freedom disappearing behind event horizons?  What does
>it mean?  Am I babbling?

No, you're just asking questions in rapid-fire succession.  :-)
I'm not the expert but I note that a recent conference proceedings has a
paper by Hawking entitled "The Density Matrix of the Universe".  (Sorry,
folks, I don't have the reference!)  I wouldn't be surprised if in
Hawking's case there is a relation to degrees of freedom disappearing
behind event horizons, because that's why an observer accelerating at a
constant rate sees the vacuum (a pure state) as blackbody radiation (a
mixed state).  (I always found this odd until I realized that all that
was going on was that since the accelerating observer doesn't get to see
all of Minkowski space his algebra of observables is a subalgebra of the
full algebra of observables; the restriction of a pure state to a
subalgebra can be a mixed state on the subalgebra ONLY IF the algebra in
question is noncommutative (i.e. only in quantum mechanics, not in 
classical mechanics).)  This is the basis of Hawking radiation and his
later predictions that virtual black holes might make time evolution
turn pure states into mixed states -- which he represents by a
"superscattering operator".  This of course would seem to give an arrow
of time.  Confusion reigns, as far as I'm concerned.
Newsgroups: sci.physics
From: jbaez@riesz.mit.edu (John C. Baez)
Subject: Re: Mirror reflections - quantum theory of light
Keywords: mirrors, reflection of light, photons
Organization: MIT Department of Mathematics, Cambridge, MA
Date: Mon, 27 Jul 92 22:48:56 GMT

NOTE: John C. Baez is the author of this article.  I am only using my
account to post this article for John as a favor - Mark Corscadden

In article <1365@yetti.UUCP> jonathan@cs.yorku.ca (Jonathan Ostroff) writes:
>I would appreciate any help in answer to the following question.
>
>According to the quantum theory of light, when I see a reflection of
>myself in a mirror, am I seeing the original photon stream as it left
>me.
>
>Or, am I seeing new photons. 

When one treats photons quantum mechanically one of the most important
things about them is that there is no way to tell photons apart, in a
very strong sense, so that there is no experimental meaning to the
question of whether the reflected photons are "old" or "new" -- there's
no way to label a photon.

To be a bit more precise, if two photons have the same momentum and spin
they are indistinguishable.  Of course the photons coming back at you
have the opposite momentum so if you like they are different from the
original ones, but that's no surprise, mainly a matter of words.

John Baez
Xref: sparky sci.physics:12089 sci.materials:585
From: rcj@lhdsy1.lahabra.chevron.com (R.C. Jones)
Newsgroups: sci.physics,sci.materials
Subject: Super Conducting Supercollider
Keywords: SCS PBS Rustum Schwitters Politics?
Date: 31 Jul 92 03:57:19 GMT
Followup-To: sci.materials
Organization: Chevron, La Habra, CA


I know that the Macneil Leherer hour on PBS is
a political program, but I can't help asking if
my ears  heard Rustum Roy say " Nobel Laureates in
physics! Who cares about them. "
What are the more scientific opinions about the value
of the Super Conducting SuperCollider program?

-- 
        |______________________________________________________________| 
||||||||| Dik Jones, Advanced Systems        Internet: rcj@Chevron.com |
        | Chevron Oil Field Research Co.           Tel: (310) 694-7056 | 
        | La Habra, California 90633-0446          Fax: (310) 694-7063 |  
Newsgroups: sci.physics
From: dwr2560@zeus.tamu.edu (RING, DAVID WAYNE)
Subject: Re: Defining Photons
News-Software: VAX/VMS VNEWS 1.41    
Keywords: Relating photons E=MC^2 criticism
Organization: Texas A&M University, Academic Computing Services
Distribution: na
Date: Tue, 28 Jul 1992 23:33:00 GMT

I write...
>>? It follows a definite path, even if it was prepared as a plane wave. It
>>will not interfere with other paths. What does the poor guy have to do to
>>prove he's classical?

jac@ds8.scri.fsu.edu (Jim Carr) writes...
>There is a very nice argument on the question of "how can it be that 
>a quantum particle whose scattering is described by a probability 
>distribution can be seen as a well-defined track in a detector" in 
>Schiff's _Quantum Mechanics_ on page 335 (and introduced on page 17 as 
>one of the problems one must deal with when understanding wave-particle 
>duality).  The problem is basically that a fast particle with a definite 
>momentum cannot be localized in space and yet leaves a nice track....

>The solution is to consider the detector and projectile as a single system, 
>but I will not try to repeat it all here.  Schiff says it very well.  His 
>reference is to Heisenberg (1930) pages 66-76 for the calculation.

He doesn't relly present it as a problem, but says it is "surprising at
first." He gives two approaches where the electron is in a wave packet
and "well localized". In the third approach (which is not referred to as a
'solution'), the only difference is that the 'observer' is not present,
i.e. the scientist has not opened the box. The chamber is part of the system.

This is analogous to Schroedinger's Cat, on a smaller scale. Before you
open the box, the particle comes through and the system becomes a
superposition of different tracks, each correlated so that it points in
the direction of momentum of the incident particle. When you open the box
you only see one track.

However one interprets it, I don't think the answer would come out different
if the particle were a boson.

Dave Ring
dwr2560@zeus.tamu.edu
From: mcirvin@husc8.harvard.edu (Mcirvin)
Newsgroups: sci.physics
Subject: Re: Quantum Cosmological Boundaries and Determinisim?
Date: 23 Jul 92 00:38:12 GMT
Article-I.D.: husc8.mcirvin.711851892

MRG3@psuvm.psu.edu writes:
>A quick comment on the role of the wavefunction/density matrix
>in consistent histories (ala Hartle & Gell-Mann):
>There is an initial condition (i.e. initial density operator) to be specified
>in the decoherence functional.  The initial conditions will  determine in part
>which histories decohere, and are quasi-classical.  The specific dynamics, and
>choice of coarse graining will also be important.

This is interesting.  I assumed that the initial density operator was
in fact a partial description of some pure state, unknown because of
our ignorance of the microscopic variables-- like an ensemble of experiments
repeatedly performed in which controllable variables interact with a
complicated environment.  You get a diagonal density matrix for the
macroscopic variables after decoherence, but in this view the state
after any one measurement would actually be some unknown superposition of
the various eigenstates of the measured observable, with the density
matrix giving average results.  Someone recently mentioned that in 
quantum cosmology, though, there might be such a thing as a truly mixed
state-- that the universe might be describable only by a density matrix,
not a single state vector or wave function.  Is this related to the idea
of degrees of freedom disappearing behind event horizons?  What does
it mean?  Am I babbling?

-- 
Matt McIrvin   mcirvin@husc.harvard.edu   Long live short .sigs
Newsgroups: sci.physics
From: jbaez@riesz.mit.edu (John C. Baez)
Subject: Re: ***********MIND-BLOWING GEDANKENEXPERIMENT**********
Organization: MIT Department of Mathematics, Cambridge, MA
Date: Mon, 27 Jul 92 21:41:11 GMT

NOTE: John C. Baez is the author of this article.  I am only using my
account to post this article for John as a favor - Mark Corscadden

In article <2387@nic.cerf.net> mitsu@nic.cerf.net (Mitsuharu Hadeishi) writes:

>Given [|v1>|v2> + |h1>|h2>]/sqrt2 , if by local unitary evolution the
>phase plate sends |v2> -> e^iphi|v2> and the have wave plate sends
>|h2> -> |v2> (half wave plates rotate plane of linear polarization by
>90 degrees says every optics text book) And I am using exactly the same
>method that Wooters and Zurek used to prove that you cannot clone a photon
>for arbitrary linear polarization in a laser amplifier which disproved Nick
>Herberts FLASH FTL communicator - then evidently by the linearity, unitarity
>and superposition principles and by elementary algebra of the distributive
>law for kets
>The initial entangled state [v1>|v2> + |h1>|h2>]/sqrt2 ->
>[|v1> + e^iphi|h1>]|v2>/sqrt2 probability is conserved! p(v1,v2) = 1/2 and
>p(h1,v2) = 1/2 { p(v1,h2) = 0, p(h1,h2) = 0, p(v1) = 1/2, p(h1) = 1/2,
>p(v2) = 1, p(h2) = 0} so what is this garbage that probability is not
>conserved. What false nonsense. 

Calm down please.  There is no unitary operator such that for all h1,h2,
v1,v2, the vector  

(|v1>|v2> + h1>h2>)/sqrt(2)

is mapped to 

(|v1> + e^{i phi}|h1>)|v2>/sqrt(2).

This is easily seen as follows.  Unitary operators are one-to-one.  The
map you write down sends vectors with different h2's to the same thing
(since h2 doesn't even appear in the second formula).  So it is not
one-to-one hence not unitary.

In QM one often argues for unitarity on the basis of conservation of
probability so I think the earlier remark about nonconservation of
probability was just a way of saying what I just said: there's no
unitary operator that does what you suggest, so it doesn't seem like a
physically possible process.

John Baez
From: bvickers@valentine.ics.uci.edu (Brett J. Vickers)
Subject: Re: Noah's formation: The rainbow
Newsgroups: sci.physics
Reply-To: bvickers@ics.uci.edu (Brett J. Vickers)
Organization: Univ. of Calif., Irvine, Info. & Computer Sci. Dept.
Date: 22 Jul 92 23:28:23 GMT
Distribution: sci

peterk@public.sub.org (Peter Kittel) writes:
>Is it only me or does the sky beneath a rainbow also appear lighter
>to others than the sky above a rainbow (or wait, was it the other way
>around?)? But anyway, for my eye there is definitely a jump in
>brightness of the background sky (normally rain clouds) from beneath
>to above the rainbow. Any explanation for this?

Optical illusion?  Two fields of the same color, separated by a line
of a brighter or darker color, give the optical illusion that one half
is lighter than the other.  The trick is to cover the line and see that
they are the same.  I've never tried this with a rainbow.

--
 ___            _    _     _  _        _
(  _) ___ ___ _( )__( )_  ( )( ) o  __( ) _  ___  ___  ___
(___)(_) (__=) (_)_ (_)_   (__) (_)(_((_)(_'(__=)(_) _(_)
Brett Vickers (bvickers@ics.uci.edu)
From: alexa@hpnmdla.sr.hp.com (Alexander Anger)
Date: Wed, 22 Jul 1992 02:36:45 GMT
Subject: Re: The Future of Physics
Organization: Hewlett-Packard, Santa Rosa, CA
From: srw@horus.ps.uci.edu (Steven White)
Subject: Re: Renormalization Group
Newsgroups: sci.physics
Reply-To: srw@horus.ps.uci.edu (Steven White)
Organization: University of California, Irvine
Distribution: world,local
Date: 31 Jul 92 16:42:28 GMT

In article <1992Jul30.150435@ece.arizona.edu>, nadar@ece.arizona.edu (Mariappan S. Nadar) writes:
|> 	I was wondering if someone could provide me with references to
|> Renormalization Group theory in Statistical Physics.
|> 
|> 	My knowledge in Physics is limited to the undergraduate curriculum
|> in Engineering.
|> 
|> 	So I would prefer references (articles) of the "popular science" type.
|> 	
|> 							Mariappan S. Nadar

K.G. Wilson, who for the most part invented the renormalization group,
wrote an article for Scientific American. I don't have the reference
at the moment, but I think it would be late 70's or very early 80's.

I'm not sure, however, that you will find it especially enlightening.
The renormalization group is a little hard to describe at an elementary
level.

						Steve White
From: andrew@rentec.com (Andrew Mullhaupt)
Newsgroups: sci.physics
Subject: Re: Chaos
Date: 22 Jul 92 16:53:15 GMT
Organization: Renaissance Technologies Corp., Setauket, NY.

In article <1992Jul21.174653.28962@ucsu.Colorado.EDU> hatay@spot.Colorado.EDU (Ferhat F. Hatay) writes:
>Talking about the low-dimensional system: Can I bring the 
>work of Glauser and his coworkers to your attention?
>In this line of work, they use the Proper Orthogonal
>Decomposition idea of Lumley to turbulent flows. 
>POD modes are obtained either experimentally or numerically. 

>Does anyone think this kind of work might provide a 
>link between chaos and turbulence (in fluids) ?

Sure. M. Ghil and R. Vautard have worked out a similar kind of EOF which
is applied to climate forecasting (in particular the El Nino - Southern
Oscillation) I have no doubt that Ghil and his collaborators will have other
links in the literature by now.

It's hard to pass judgement on whether or not this kind of connection
'establishes' chaos in fluids, since EOF analysis is not predicated on
deterministic chaos. Neither are nearest neighbors techniques.

For those really resistant to the idea that chaos is relevant to fluids,
they should look at the kind of experiments A. Libchaber has done.

For those who want to insist that turbulence is 'nothing but' chaos, they
should look at experiments like H. Swinney has done.

As anyone in their right scientific mind would have guessed - a problem that
foxed Heisenberg, G.I. Taylor, Poincare, Landau and many others - is a problem
with more than a two line solution.

Later,
Andrew Mullhaupt
a
From: ethan@ut-emx.uucp (Ethan Tecumseh Vishniac)
Newsgroups: sci.physics
Subject: Re: "What's New" July-24-1992
Date: 28 Jul 92 18:29:40 GMT
Organization: The University of Texas at Austin; Austin, Texas


>>	WHAT'S NEW, Friday, 24 July 1992                   Washington, DC
>>
>>	1. PHYSICISTS IN EUROPE, JAPAN AND CANADA OPPOSE SPACE STATION!

>>	3. SENATE COMMITTEE RESTORES $550M TO THE SUPERCOLLIDER IN FY 93!

>     Is this from the "It may be pork, but its OUR pork" file?

>                                   dale bass

Give me a break.  This falls under the heading of `at least it's science'.

Besides, I would have written it up in almost the same way, and I think
that the SSC is overpriced.

Haven't we just about beaten this one to death?
-- 
"Quis tamen tale studium, quo ad primam omnium rerum causam evehimur,
tamquam inutile aut contemnendum detractare ac deprimere ausit?"-Bridel
Ethan T. Vishniac, Dept. of Astronomy, The University of Texas at Austin
Austin, Texas, 78712                   ethan@astro.as.utexas.edu
Newsgroups: sci.physics
From: matmcinn@nuscc.nus.sg (Mcinnes B T (Dr))
Subject: Re: non-orientable cosmology
Organization: National University of Singapore
Date: Tue, 28 Jul 1992 03:14:12 GMT

No,you are thinking of cosmologies with 3-spheres as spatial sections.
Ellis considers the case of flat compact spatial sections.
Newsgroups: sci.physics
From: jmc@SAIL.Stanford.EDU (John McCarthy)
Subject: Re: "What's New" July-24-1992
Reply-To: jmc@cs.Stanford.EDU
Organization: Computer Science Department, Stanford University
Date: 25 Jul 92 12:39:47

My opinion is that the physicists are mistaken about the space
station, imagining they could get some of the money saved by the
cancellation.

The reason for the space station is only marginally science and
even more marginally prestige.  The space station is a start on
human expansion into the solar system.  That is what generates
the public support for it.  It may not be the best design, but
it's the only design we have, and the scientist opposition has
made matters worse, not better.

The physicists have had their heads wedged about space ever since
World War II, perhaps from guilt feelings about the atomic bomb.
In 1955 they PSAC persuaded Eisenhower to plan for an 18 pound
satellite for the International Geophysical Year.  For some
imagined reason of purity, the project was not to use the
rockets developed for military purpose.  In 1957 the Soviets
launched the 200 pound Sputnik I shortly followed by the
2000 pound Sputnik II.  The first American orbital launch wasn't the
pure Vanguard which blew up on the pad the first two times
but the military based satellite cobbled together in a month or
two when Eisenhower finally allowed it.

I favor both, but maybe the space station and the collider will kill
each other off.
--
John McCarthy, Computer Science Department, Stanford, CA 94305
*
He who refuses to do arithmetic is doomed to talk nonsense.
From: jmc@SAIL.Stanford.EDU (John McCarthy)
Subject: Re: Cost of public vs. private transportation
Reply-To: jmc@cs.Stanford.EDU
Organization: Computer Science Department, Stanford University
Date: 24 Jul 92 23:30:04

Many years ago, public transportation was profitable.  One of the
problems that killed its profitability was regulation of fares.  It
was always possible for a lawyer or politician to gain a reputation
by fighting the evil railroads.  They fought the evil railroads in
the public interest to the point of driving every one of the eastern
railroads bankrupt.

I would bet that public transportation is profitable in some parts
of the world and even in some parts of the U.S.  Greyhound made
money, at least until the bargain air fares came along.
--
John McCarthy, Computer Science Department, Stanford, CA 94305
*
He who refuses to do arithmetic is doomed to talk nonsense.
From: bill@wsuaix.csc.wsu.edu (William E. Johns;S23015)
Newsgroups: sci.physics
Subject: Re: density of commonly used materials
Date: 29 Jul 92 17:53:55 GMT
Organization: Washington State University

In article <25933@life.ai.mit.edu> sundar@ai.mit.edu writes:
>Hi, I am interested in finding out the densities (ranges) of commonly used 
>materials (starting from things like Aluminium, Steel, Wood etc. to
>rubbers and plastics). Is there a handbook of physical constants I can
>refer to? Is any such information available online?
>
>Thanks much.

The CRC MATERIALS SCIENCE and ENGINEERING HANDBOOK has all this and so much
more you can spend hours just wandering around all the info.

Ride Free,

Bill

ps oh yeah, by James Shackelford and Willam Alexander
________________________________________________________________
bill@wsuaix.csc.wsu.edu if you feel compelled to send email
johnsw@wsuvm1.csc.wsu.edu if you seriously expect an answer
AMA #500924   DoD #00314   WMTC #0002   SR= 2.125
FJ1200 R100GS/PD 740GLE  KotV KotRR KotD #0001  :-)
\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/

If you understand, things are just as they are;
If you do not understand, things are just as they are.
                                                        Zen verse
Xref: sparky sci.physics:11976 sci.astro:8451 sci.philosophy.tech:2905 talk.religion.misc:12981
From: billn@hpcvaac.cv.hp.com (bill nelson)
Newsgroups: sci.physics,sci.astro,sci.philosophy.tech,talk.religion.misc
Subject: Re: Structure of Time
Date: 29 Jul 92 19:07:32 GMT
Organization: Hewlett-Packard Company, Corvallis, Oregon USA

matmcinn@nuscc.nus.sg (Mcinnes B T (Dr)) writes:
: Should we really believe that somebody reported this guy to his
: employer? Are there really such bastards out there?

Who knows? Yes, there are such people out there.

Bill
From: barry@arnold.math.ucla.edu (Barry Merriman)
Newsgroups: sci.physics
Subject: Re: Blue Sky
Date: 23 Jul 92 01:09:53 GMT
Organization: UCLA, Mathematics Department

In article <10018@vice.ICO.TEK.COM> hall@vice.ICO.TEK.COM (Hal Lillywhite)  
writes:
> In article <9930@sun13.scri.fsu.edu> jac@ds8.scri.fsu.edu (Jim Carr) writes:
> 
> ....
> >George did that routine before blue-corn became popular enough to 
> >show up as corn flakes as well as tortillas, or squid-ink pasta made 
> >it into american grocery stores.  Interesting that there are blue birds 
> >and flowers but not blue animals; where is a biologist when we need one! 
> 
> And I find it peculiar that although there are blue birds, there are
> no blue raptors that I know of.  Can you imagine the advantage a sky-
> blue hawk would have?  His prey would have a very difficult time seeing 
> him until it was too late.  I wonder why such an obvious advantage 
> seems not to have developed.

Actually, he should be blue on the bottom and dark on top,
so that he ends up blending in when viewed from above or below.
Thats "why" fish are silver on the bottom and dark on top, perhaps



--
Barry Merriman
UCLA Dept. of Math
UCLA Inst. for Fusion and Plasma Research
barry@math.ucla.edu (Internet; NeXTMail is welcome)