HDTenEightyP/NetNews huggingface dataset:
From: carlip@landau.ucdavis.edu (Steve Carlip)
Newsgroups: sci.physics
Subject: Re: Did electric/magnetic symmetry "break"?
Date: 5 Sep 92 23:40:29 GMT
Organization: Physics, UC Davis

In article <1992Sep5.073528.16705@asl.dl.nec.com> terry@aslws01.asl.dl.nec.com (Terry Bollinger) writes:
> [...]
> o  Can the assymmetry of [electric:1] and [magnetic:63] be defined
>    mathematically as a "broken symmetry" -- that is, that at some time
>    very early in the history of the universe *either* of the two fields
>    could have been associated with charges of one unit, with the other
>    one being relegated off to the lesser role of what we now call the
>    "magnetic" field? [...]

There are two kinds of broken symmetries in physics.  A "spontaneously
broken symmetry" is one in which the action (or the field equations)
are exactly symmetric, but the ground state has a smaller (or no) 
symmetry.  An "explicitly broken symmetry" is one in which part of 
the action is symmetric, but part is not.  A natural ferromagnet is an
example of spontaneous symmetry breaking --- nothing in the field
equations picks out a direction of magnetization, but the magnetic
fields of atoms "spontaneously" align in some (arbitrary) direction.
If you put your piece of iron in an external magnetic field, on the
other hand, you get explicit symmetry breaking --- the preferred
direction is picked out by the direction of the external field, and
is no longer arbitrary.

The electromagenetic symmetry you are asking about is called duality.  
In the absence of charged matter, you can freely rotate the electric and
magnetic fields into each other.  Charged sources provide an _explicit_
symmetry-breaking, by uniquely picking out one "direction" to couple
to.  This isn't the kind of broken symmetry you're asking about, I
think; for instance, there's no phase transition between a symmetric
and a nonsymmetric ground state. 

A natural question is whether there's some way to reformulate the theory
so that this explicit symmetry-breaking is replaced by a spontaneous
symmetry-breaking.  As far as I can tell, there isn't --- the coupling
of electromagnetism and matter takes place through the electromagnetic
potential, while duality is a symmetry only at the level of the
electromagnetic field.  But it would be fun to think about more...

Steve Carlip
carlip@dirac.ucdavis.edu
Newsgroups: sci.physics
From: hagerman@ece.cmu.edu (John Hagerman)
Subject: Re: Did electric/magnetic symmetry "break"?
Organization: Carnegie Mellon University
	<26148@dog.ee.lbl.gov>
Distribution: na
Date: Mon, 7 Sep 1992 22:12:40 GMT

In article <26148@dog.ee.lbl.gov> sichase@csa3.lbl.gov (SCOTT I CHASE) writes:
>
>In article <5294@tuegate.tue.nl>, johan@blade.stack.urc.tue.nl (Johan Wevers) writes...
>
>>******************************************************************** 
>>* J.C.A. Wevers                *         u\  _\       /e+        2 * 
>>* johan@blade.stack.urc.tue.nl *     1 |   \ u \  X  /         |   * 
>>******************************** P = - |    >   >---<     + ...|   * 
>>*     The only nature of       *     N |   /   /     \         |   * 
>>*     reality is physics       *         u/   /d     u\            *
>>********************************************************************
>
>Your .sig has inspired me to write something about the status of proton decay 
>one of these days.

This reminds me of a T-shirt I saw at the amusement park yesterday:

    Everything is possible
       Nothing is real

- John
Xref: sparky sci.physics:14619 sci.math:11405
From: weemba@sagi.wistar.upenn.edu (Matthew P Wiener)
Newsgroups: sci.physics,sci.math
Subject: Re: Applied inconsistency
Date: 14 Sep 92 14:20:22 GMT
Reply-To: weemba@sagi.wistar.upenn.edu (Matthew P Wiener)
Followup-To: sci.physics
Organization: The Wistar Institute of Anatomy and Biology
In-reply-to: jbaez@riesz.mit.edu (John C. Baez)

In article <1992Sep14.031203.26675@galois.mit.edu>, jbaez@riesz (John C. Baez) writes:
>>[Regarding physicists' reactions to a rock solid TOE, except for the
>> small matter of logical inconsistency.]

>Anyway, while this would make great science fiction, we can't really tell
>what would happen in such a remote eventuality.

I don't think we need to invoke science fiction.  Heaviside and Dirac used
distributions and left it to mathematicians to figure it out.  Physicists
continue to use things with rather incomplete mathematical foundations (eg,
path integrals, renormalization), and simply don't care much to notice if
they happen to be using a version that has been officially explained or
not.  My favorite is zeta function renormalization: 1+2+3+4+... = zeta(-1),
no problem.  I'm sure that someday this will make perfectly rigorous sense,
in the sense that 1-2+4-8+...=1/(1--1) is 2-adically rigorous.

>In short, I believe mathematical physics, insofar as it is really
>physics, to be fairly insensitive to the axioms of math one uses. 

The same can be said about most mathematics.  John Horton Conway has
his Mathematicians' Liberation Movement in the middle of ON NUMBERS AND
GAMES.  His point was that it was a distracting side issue to figure out
how to make his liberal use of proper classes legitimate according to
ZFC.  Hirzebruch and Grothendieck, two outstanding mathematicians, could
have used some of that attitude--their work is scarred where they hedge
around their introduction to K-theory or categories or other proper class
manipulations.
-- 
-Matthew P Wiener (weemba@sagi.wistar.upenn.edu)
From: weemba@sagi.wistar.upenn.edu (Matthew P Wiener)
Newsgroups: sci.physics
Subject: Re: Not quite so Black Holes...
Date: 13 Sep 92 21:04:31 GMT
Reply-To: weemba@sagi.wistar.upenn.edu (Matthew P Wiener)
Organization: The Wistar Institute of Anatomy and Biology
In-reply-to: rabjab@golem.ucsd.edu (Jeff Bytof)

In article <rabjab.96.0@golem.ucsd.edu>, rabjab@golem (Jeff Bytof) writes:
>If an alternative to General Relativity is developed, and leads to
>a prediction that collapsed stars do not end up getting crunched into
>a singularity, what might be the resulting physics of such an object,
>which might be much denser than a neutron star?

Obviously that would depend on the alternate gravity.  Maybe Will's
book includes some examples, I don't remember.  Within GR, there are
mumblings about quark stars.
-- 
-Matthew P Wiener (weemba@sagi.wistar.upenn.edu)
From: matmcinn@nuscc.nus.sg (Mcinnes B T (Dr))
Newsgroups: sci.physics
Subject: What do we know about choice of groups?
Date: 11 Sep 92 02:15:51 GMT
Organization: National University of Singapore

Suppose that the standard theory is right, and that the gauge group of
the world is "SU3xSU2xU1"  [actually S[ U2xU3 ] of course]. Then we will
have to understand why this particular group was chosen from infinitely
many others. The same problem arises, albeit less urgently, if GUTs are
correct: why SO[10]  [actually Spin[10] of course]  rather than SO[110]
?
What ideas have been proposed to solve this problem?
From: folta@cs.umd.edu (Wayne Folta)
Newsgroups: sci.physics
Subject: Re: Why Do Mirrors Reverse Left/Right and Not Up/Down?
Date: 7 Sep 92 13:42:21 GMT
Distribution: na
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742

I have thought about this a lot and come to the conclusion that the reason that
we mentally rotate ourselves is that we view the mirror as if it were a window!
We look "through" the looking glass as if looking into a scene in another room,
and this results in reversing things left-right. It has nothing to do with
human symmetry as it happens with all objects.

If I also might add an experiment to the FAQ. It dramatically illustrated to
me that the mirror did not rotate anything, much less asymmetrically:

   This experiment can be done in a small room or hallway with a mirror on
   one wall. Write the word "EVERY" on a piece of paper in letters large enough
   to to be clear when viewed across the room, looking in the mirror.

   Stand perpendicular to the wall with the mirror, with the mirror to your
   right (or left) and slightly ahead of you. Place the word so that it is on
   the wall to your left (or right) and far enough away that you can see its
   reflection in the mirror. (If this is not clear, see figure 1.)

   The word will appear reversed left-right. Now look more closely, and you will
   see that "left-right" is, due to the positioning of the mirror/word, actually
   "close-far". Now look at the paper, and you see that the closest letter to
   you is "E". Look in the mirror, and behold that the closest letter to you
   is also the "E". This is not some trick at the scale of the letters, as it
   occurs at every scale. Look closely at the "E" and you will see that in
   both the reflection and the paper, the prongs of the "E" point away from
   you. Note also that up-down reversal has not occured either: the "V" points
   the same way in both.

   I actually discovered this (for me) enlightening experiment in our bathroom.
   I didn't actually move around the room, but sat right in front of the mirror.
   I am not sure if physically moving and rotating (as phrased above) makes the
   effect stronger or weaker. (My mental movements allowed me to see the
   effect while still always seeing a distinct left-right reversal. It also
   allows you to move around the room looking, say, from the ceiling.)

   If others find this experiment enlightening, I would venture that it is
   because it changes left-right to near-far and near-far is invariant whether
   looking into a scene or being in a scene, while left-right is relative.
   ("Everyone on my right, your left...")

	 U   <--- You

    |   <-------- Mirror      Figure 1
    |

	    | <-- Word
	    |
-- 


Wayne Folta          (folta@cs.umd.edu  128.8.128.8)
Newsgroups: sci.physics
From: jlg@cochiti.lanl.gov (Jim Giles)
Subject: Re: Hidden variable theories, was: Uncertainty Princi
Organization: Los Alamos National Laboratory
Date: Fri, 11 Sep 1992 18:51:51 GMT

In article <270@mtnmath.UUCP>, paul@mtnmath.UUCP (Paul Budnik) writes:
|> [...]
|> What is measured in test of Bell's inequality is the correlation between
|> manipulations of a polarizer and particle detections. The correlations
|> cannot be carried by the particles because the manipulations do not
|> occur until after the particles have separated. [...]

But, hidden variable theories (even conventional ones) *ALSO* predict
such correlations.  They just predict them with different *distributions*.
If *information* is transferred instantaneously in the real quantum
system that we actually see then it must *also* have been said to be 
instantaneously transmitted *if* the hidden variables theories had 
been *confirmed*.  This aspect of the two theories is identical.
*Both* predict correlations - even if the polarizers are manipulated
a space-like interval apart.  They just predict different *distributions*
of the correlations.  Period.

|> [...]                                               According to quantum
|> mechanics manipulating a local polarizer can instantaneously *influence*
|> what happens a billion light years away. This is experimentally detectable
|> and the bit rate of data being transferred can be measured. The way this
|> is verified experimentally is by comparing two sequences of 
|> detections and two sequences of polarizer manipulations. This can
|> only be done after the fact. [...]

Then the information is carried by the signal which transmits the sequences
to the rendezvous for comparison!  If *information* were being transfered
through the apparatus then I should be able to send messages through it
*at*the*time*of*the*experiment*!!

-- 
J. Giles
From: mcirvin@husc8.harvard.edu (Mcirvin)
Newsgroups: sci.physics
Subject: Re: Did electric/magnetic symmetry "break"?
Date: 8 Sep 92 02:26:45 GMT
 <1992Sep7.214235.24769@galois.mit.edu> <1992Sep8.012930.25239@galois.mit.edu>

jbaez@riesz.mit.edu (John C. Baez) writes:

>Afficionados of those who plunged in where angels feared to tread will
>have to check out Eddington's book in which he tried to "deduce" that
>the fine structure constant was exactly 136.  Then it turned out to be
>137 and he realized he'd left one something-or-other out.  Well, then
>it turned out not to be exactly 137 either. 

And when people started understanding what was really going on
with renormalization, it became apparent that 1/137.036 probably
isn't a special number anyway-- the fine structure constant has
different values at higher energies, values which really have as
much a claim to correctness as the one we measure at arbitrarily
low energies and long distances.  Attempts to deduce the fine
structure constant from first principles are consequently less
common today, unless you count the ambition of string theorists to
deduce all the coupling constants from first principles someday.
-- 
Matt McIrvin, Cambridge, Massachusetts, USA 
Newsgroups: sci.physics
From: prim!dave@germany.eu.net (Dave Griffiths)
Subject: Re: Uncertainty Principle [T.Bollinger => LONG]
Organization: Primitive Software Ltd.
Date: Mon, 7 Sep 1992 00:15:18 GMT

In article <1992Sep5.071519.16554@asl.dl.nec.com> terry@aslws01.asl.dl.nec.com (Terry Bollinger) writes:
>
>Dr. Richard Feynman was NOT a hidden parameter type, and the recent results
>of experiments (e.g., Aspect) designed to test whether hidden variable might
>lurk at the heart of QM seem to indicate that the answere is NO -- you cannot
>do such things without violating both the rules of QM and explicitly observed
>behavior in such experiments.

Can you (hopefully without getting too technical!) explain what is meant by
"hidden variables"? I have seen it mentioned many times, but without a
precise definition of the class of theories it represents.

I don't think it's enough to just accept QM the way it is. It seems to have
horrible flaws (the collapse of the wave function when "observed", whatever
"observed" means) and is probably a bad model. There is surely room for a
better theory that explains our observations but without quite so much
wierdness.

What class of theories does "hidden variables" refer to?

Dave Griffiths
Newsgroups: sci.physics
From: jbaez@riesz.mit.edu (John C. Baez)
Subject: Re: Hidden variable theories, was: Uncertainty Princi
Organization: MIT Department of Mathematics, Cambridge, MA
Date: Sat, 12 Sep 92 02:06:32 GMT

From galois!snorkelwacker.mit.edu!spool.mu.edu!uunet!mtnmath!paul Fri Sep 11 20:17:18 EDT 1992
Article: 20187 of sci.physics
From: jbaez@riesz.mit.edu (John C. Baez)
Subject: Re: Question of Theory of Everything (or Grand Unified theory)
Organization: MIT Department of Mathematics, Cambridge, MA
Date: Tue, 8 Sep 92 18:25:55 GMT

In article <1992Sep8.023027.15883@nuscc.nus.sg> matmcinn@nuscc.nus.sg (Mcinnes B T (Dr)) writes:
>Please excuse me if you have already debated the hell out of this
>one......but I would like to make the following observation. It strikes
>me that [eg] superstring theory is not easy to understand.

To my mind that's more evidence for why it can't be the fundamental 
theory of physics, at least in its present form.  This is a purely
"esthetic" argument, though, based on the prejudice that the laws of
nature should be simple, so I don't take it too seriously.

 Suppose that
>in the 80's it had turned out that string theory is right. Then we would
>have to conclude that the universe is incomprehensible to all of
>humanity except for a tiny coterie of people. Now: is it not truly
>astounding that the complexity of the universe is so precisely
>calibrated to the intelligence of homo sapiens? So that it is just
>barely within our comprehension, to the extent that a few hundred of us
>can understand it? Aren't we lucky? 

It's worth noting also that Newtonian mechanics was only comprehensible
to a tiny coterie of people when it was first developed.  Later,
education brought it within the grasp of many people, although lately in
America the set of people who can understand it is dwindling back to a
tiny coterie again.  My point is that Newtonian mechanics or string
theory is not actually nearly as complicated as the skill of, say, being
a politician and fooling most of the people most of the time.  Work in
AI has shown that often the things we THINK are hard to do are easier to
teach a computer to do than the things we think are easy.  It's just
that people more commonly use their intelligence on social skills than
on math and physics.  

>Would one not expect a priori that
>the universe should be either easily comprehensible to all, or vastly
>beyond the intellect of even a Fields medallist?  :)

It's probably both.  I imagine that the basic laws are very simple but
deducing all their consequences is essentially impossible.
Newsgroups: sci.physics
From: allenk@harry.ugcs.caltech.edu (Allen Knutson)
Subject: Color of electric charges (silly question)
Organization: California Institute of Technology, Pasadena
Distribution: na
Date: Sat, 12 Sep 1992 20:08:49 GMT

John Baez mentions a cartoon:

>Near the article is a cartoon titled "When the Senate voted to revive
>the $8-billion Super Collider".  It shows a bunch of Senators streaming
>down the stairs, saying:
...
>"Hey, can I get some protons to show my constituents?"
>"No problem... I'll talk to some people..."
>"Red ones!"
>"Absolutely, for 8 billion we should get some red ones..."

Whenever I see pictures of electrons and protons, electrons are green and
protons are red. (Please don't anyone confuse this with colors of quarks!)
I remember it being that way in Mr. Tomkins, I think: does the history go
back further than that? Has anyone seen the convention reversed?
								Allen K.
Newsgroups: sci.physics
From: jcf@world.std.com (Joseph C Fineman)
Subject: Re: Why Do Mirrors Reverse Left/Right and Not Up/Down?
Organization: The World Public Access UNIX, Brookline, MA
Date: Thu, 10 Sep 1992 01:28:20 GMT

Right!  Here is another web of words:  Mirrors do not reverse left &
right *or* up & down: they reverse forward & backward (or, more precisely,
they reverse the direction perpendicular to them: a horizontal mirror
*does* reverse up & down).  But people in real life exchange their
front & back sides by rotating, not by popping thru themselves; therefore,
we say "the person in the mirror has raised his left hand, whereas I
have raised my right hand", rather than "the person in the mirror has
his face on the back of his head, rather than...".  In the case of a
printed page, if the page is transparent, so that you can read it in the
mirror without turning it over, then it appear unreversed both in the
real world and in the mirror; if you have to turn it over, then *you*
make the choice of reversing left & right or top & bottom, and you
choose the former because you have the person in the mirror in mind.
Newsgroups: sci.physics,sci.math
From: pratt@Sunburn.Stanford.EDU (Vaughan R. Pratt)
Subject: Re: Report on Philosophies of Physicists
Organization: Computer Science Department,  Stanford University.
Date: Tue, 15 Sep 1992 03:28:00 GMT

In article <TORKEL.92Sep14233501@bast.sics.se> torkel@sics.se (Torkel Franzen) writes:
>So, setting aside and completely
>ignoring 19th century mathematicians, all you need to do to meet any
>challenge of mine is to explain what you yourself were talking about
>in your original article as you spoke of "a foundation for
>mathematics".

Well, I don't see how one could read my "mathematical community finding
that Cantor's theory provided an attractive and workable foundation for
mathematics" as their finding this for *all* mathematics unless they
actually *did* all mathematics.  So just from context this part *has*
to mean "their mathematics".  And that's all I intended in that
particular sentence.  (I think this was the sentence you originally
objected to, yes?)  Sorry if my previous attempts at conveying this
weren't clear.

-- 
======================================================| God found the positive
Vaughan Pratt   pratt@cs.Stanford.EDU   415-494-2545  | integers, zero was
======================================================| there when He arrived.
From: gilligan@bldrdoc.gov (Jonathan M. Gilligan)
Newsgroups: sci.physics
Subject: Re: Where do physics graduates look for work?
Date: 10 Sep 92 23:49:47 GMT
Organization: National Institute of Standards and Technology

In article <1992Sep10.153848.1215@nntpd.lkg.dec.com> abbasi@star.enet.dec.com writes:
>
>Ok, you worked hard to get your physics degree, now what do you do?
>where do you look for work? when I mean work, I mean physics/science
>related, not flipping burgers.
>
>are there actually physics/science work out there?
>
>what is best references/papers/magazines to help in this regard?

There is far less work for trained physicists (and other scientists)
than there are trained physicists. That's why there are hundreds of
applicants for practically every position that's advertised. (The
winners, I believe, are Amherst College in physics and the University
of Washington in Computer Science, who received over 800 and 1000
applicants, respectively, for advertised faculty positions.)

For more information on the glut of trained scientists, read ``Signs
of tighter job market grow; more than recession at work,'' (Physics
Today March 1992, p. 55) and ``Condensed matter physics in a market
economy,'' (Physics Today, May 1992, p. 40).

There is a growing (now over 1000 subscribers) unmoderated electronic
newsletter called ``Young Scientists' Network,'' to which you can
subscribe by sending a request to John D. Sahr at
ysn-adm@zoyd.ee.washington.edu.  (Send subscription requests to
ysn-adm, not ysn, or they will go out to all subscribers.) YSN
discusses the job shortage and encourages its members to fight the
false perception that the nation is facing a shortage of scientists
and engineers. A few notices of job openings are also posted to the
group.

As to finding a job, it is common for an advertisement of a job in
physics to appear in print after the position is already filled. The
delays in printing are often responsible, as is the legal requirement
that to comply with equal employment opportunity laws, a department
must make a pro forma public announcement of any job opening, even if
they already know who they want to hire.  Thus, to get a job, in
addition to sending out responses to advertised jobs, you should call
around to senior people you know at physics departments and industrial
laboratories asking about openings.

---Jon
-- 

Disclaimer --- The government probably disagrees with my opinions.
From: mcirvin@husc8.harvard.edu (Mcirvin)
Newsgroups: sci.physics
Subject: Re: Why Do Mirrors Reverse Left/Right and Not Up/Down?
Date: 6 Sep 92 19:27:17 GMT
Distribution: na

sichase@csa2.lbl.gov (SCOTT I CHASE) writes:

[on apparent left-right reversal coming from bilateral symmetry]

>I think that the impression of left-right reversal depends only on the
>fact that we are *not* symmetric front to back.  When you look in the mirror,
>you imagine turning the person in the image around by 180 degrees so that
>they are looking in the same direction as you are.  This causes the in-out
>reversal of the mirror to become a left-right reversal.  And the only 
>reason that you think to do this is that your front side is so different
>than your back side - not that your left is so much like your right.

There's one more ingredient: 
The *way* you imagine turning the person in the image around is
by rotation around a vertical axis.  This depends on the fact that
when we turn around, we usually turn about a vertical axis.  It's
not so much body symmetry as locomotor behavior, and habits of orientation.

Likewise with printed words.  When you rotate a piece of paper to,
say, show the writing on it to someone standing opposite you, you
rotate it around a vertical axis so that the top of the paper is
still at the top.  Therefore you see words in a mirror as backwards
left-right rather than upside down, even though text is no more
symmetric horizontally than it is vertically.

(And, of course, if you lie on your *side* when doing these mirror
experiments, the mirror actually does appear to reverse up and down,
measured with respect to the ground!)
-- 
Matt McIrvin, Cambridge, Massachusetts, USA 
Newsgroups: sci.physics,alt.sex