HDTenEightyP/NetNews huggingface dataset:
Newsgroups: sci.physics
Subject: Re: Aristotle and the Modern Physicist
From: mcirvin@husc10.harvard.edu (Mcirvin)
Date: 28 Jul 92 15:08:19 GMT

aephraim@physics.Berkeley.EDU (Aephraim M. Steinberg) writes:

>In article <mcirvin.712271293@husc8> mcirvin@husc8.harvard.edu (Mcirvin) writes:
>%The aftermath of a cat-box experiment probably shouldn't be
>%called a *coherent* superposition in the modern sense of the
>%term, but you could indeed rig one so that the quadrupole

>I'm not really sure what makes you say this.  Certainly, the cat alone is
>not in a coherent superposition, nor is the radioactive nucleus, taken
>alone, but together, they are.  (Assuming they have not yet interacted
>with anything else.)

Well, I'm out of my depth here... the people who actually know
a lot about alternative decoherent histories and such might
be better able to explain.  Yes, if you believe that the world
is always in a pure state, and that there's no collapse, the 
outcome is a pure state as well; but it can be shown that it
becomes exponentially difficult to measure any operator whose
eigenstates vary appreciably from the macroscopic states 
corresponding to different outcomes of the experiment, as time
goes on.  In that sense the possibilities have "decohered,"
although the state still has some definite amplitude for each
macroscopic possibility (not just "cat dead" and "cat alive,"
but including different times of death for the cat).  That's
all I know about the subject, though, and I've probably
made a gross error somewhere in the description.

[About Aharonov's time machine...] 
>Am I just confusing Aharonov with Douglas Adams, or wasn't there a way
>of considering the rest of the universe to be "inside" the shell, while
>you sat "outside" it, so that everything except you would evolve backwards
>in time?  Does seem to have some problems with boundary conditions, I
>admit... but it does make for much better reading :-).

Perhaps, in which case it really would act much like a time
machine in the traditional sense.  I wasn't aware of that.

However, there would be one difference between this and the
situation with, say, closed timelike lines:  no causality
paradoxes have to be resolved.  Nothing prevents the forward
evolution from going differently the second time around, by
your intervention.

-- 
Matt McIrvin  mcirvin@husc.harvard.edu
From: bhoughto@sedona.intel.com (Blair P. Houghton)
Newsgroups: sci.physics
Subject: Re: Destroying the Earth
Date: 29 Jul 92 22:45:29 GMT
Organization: Intel Corp., Chandler, Arizona

In article <1992Jul29.045948.22579@u.washington.edu> whit@milton.u.washington.edu (John Whitmore) writes:
>	Rs = 9e-3 M (yep, that's nine millimeters)
>I seem to recall that this calculation is off by a factor of two,

Okay, so it's a little blue marble, 1-3cm in diameter.

And it weighs as much as I do, if I'm standing on it.

				--Blair
				  "This'll fix the semanticists."
Newsgroups: sci.physics
From: crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass)
Subject: Re: "What's New" July-24-1992
Organization: University of Virginia
Date: Wed, 29 Jul 1992 02:44:03 GMT

In article <1992Jul29.012628.4238@murdoch.acc.Virginia.EDU> gsh7w@fermi.clas.Virginia.EDU (Greg Hennessy) writes:
>In article <1992Jul29.010055.3863@murdoch.acc.Virginia.EDU>
>crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass) writes: 
>#    NIH is being forced to fund study into chiropractry(?) along with the
>#    other 'alternative medicine' approaches. 
>
>"Forced"? I would consider such studies to be good. Surgeons don't
>have a monopoly in how to help people get better. Alternative methods,
>which are probably less expensive than "mainstream" medicine are good
>things if they are effective. 

     Yes 'forced'.  Meaning that they were made to do something that
     they would rather not, for good and obvious reasons.

>#    As far as astrology goes, I'd think that such widespread antiscientific
>#    beliefs would be of great interest to those in the APS apparently
>#    interested in scientific purity.  
>
>Yea, those astrologers might be after our vital bodily fluids. Come on
>Dale, this is farther then even you normally stretch a point. I have
>seen letters from the APS to newspapers asking them to put disclaimers
>on horoscopes. 

     Where?  When?  Publicity?  Studies?  Commissions?

     The position of the APS is that the space station is not 'science'
     and should not be funded as such.   I would just expect them to pursue 
     other 'science purity' issues with the same vigour.

>#    Also, I'm sure such base things as dollars never come into consideration
>#    of certain members of the APS when things like the integrity of science
>#    come into play.  After all, we have been told many times that the APS
>#    is not against SSF because of the competition for money, just because
>#    'it is not science'. 
>
>Well the only person who says that dollars never come into
>consideration is you, so you get little credit from knocking down your
>own strawman. 

     So it is competition for dollars with other programs of more
     direct interest to APS rather than the 'science-thing'?  I'm 
     shocked.

>As for the space station not being science, read todays Post and
>you'll see that Goldin's article has the first 4 non-introductory
>paragraphs being the scientific return of SSF. If Goldin is going to
>make "scientific" return the number 1 thing he talks about, it is
>quite fair to point out it ain't much science to be done, and the
>budget is better spent in other programs. 

     Agreed.  However, it is disingenuous to say that it is any different
     for SSC.  By the way, the hypocracy of the APS with regard to 
     SSF and SSC was the original subject.  It still exists.

                                 dale bass
--
C. R. Bass                                           crb7q@virginia.edu
Department of Mechanical and Aerospace Engineering
University of Virginia
Charlottesville, Virginia                            (804) 924-7926
From: cornell@sc2a.unige.ch
Newsgroups: sci.physics
Subject: Re: ... an infinite mesh of 1ohm resistors ...
Date: 31 Jul 92 09:04:18 GMT
 <1992Jul28.141407.17816@galois.mit.edu> <24327@castle.ed.ac.uk>
Organization: University of Geneva, Switzerland

In article <24327@castle.ed.ac.uk>, graeme@castle.ed.ac.uk (G J Ackland) writes:
> This source / sink argument is all very nice.
> Doesn't it give the wrong answer for a Bethe lattice though?
>   
> __/  \__
>   \__/
> __/  \__/
>   \  /  \
> 
> where the absence of cicuits mean the solution is trivially 1 ohm, but
> the three-way split of the current appears to give 2/3ohm using this
> source/sink argument.

This is a very interesting example, illustrating the physical problems of 
using appropriate boundary conditions in the Bethe lattice.  

If you start with a FINITE part of a Bethe lattice  with INSULATING 
boundary conditions and measure the resistance (over a timeascale much 
longer than the time for the circuit to fill with charge - i.e. in the 
asymptotic steady state) then you will indeed measure 1 ohm.  However, if 
you connect the boundaries to EARTH (or alternatively measure on a short 
timeascale), you will instead find a value 2/3 Ohms as the lattice grows to 
infinity.  The reason for this is  (trivially) that in the latter case the 
currents at the boundaries due to the current "source" and "sink" do not 
cancel out; in particular, you have 1/3A escaping from the left hand side 
of the lattice and 1/3 amps entering from the right-hand-side.  The two 
values correspond to different physical situations, and so there is no
contradiction.

This shows the importance of demonstrating that, in the square mesh, the 
contributions from the source and the sink cancel out at infinity.

Stephen Cornell.
From: andrew@rentec.com (Andrew Mullhaupt)
Newsgroups: sci.physics
Subject: Re: Lightning
Date: 21 Jul 92 02:41:02 GMT
Organization: Renaissance Technologies Corp., Setauket, NY.

In article <9870@sun13.scri.fsu.edu> jac@ds8.scri.fsu.edu (Jim Carr) writes:
>In article <1085@kepler1.rentec.com> andrew@rentec.com (Andrew Mullhaupt) writes:
>>
>>You hear lightning on AM radio so it isn't just DC, right? It's pretty broad
>>band, since you can get it all over the spectrum. So it's perhaps true that
>>initially the spark crosses the gap in some directional sense, there's a lot
>>of AC in a lightning strike.

>Remember, you do not need an AC current to generate an E-M wave, just a 
>time-varying current.  A DC current pulse will do just fine.  In fact, 
>something of that sort is necessary to get the broad frequency range. 

A DC current pulse has AC in it. (In some sense it doesn't mean much to
talk about pure AC or DC in this kind of situation.) The situation is
a lot like a spark across air in the lab. In these, (remember Hertz
and Marconi), there is known to be lots of AC.

Later,
Andrew Mullhaupt
Newsgroups: sci.physics
Subject: Re: Converting the masses
From: mcirvin@husc8.harvard.edu (Mcirvin)
Date: 23 Jul 92 15:01:24 GMT
 > <1992Jul22.193837.18095@sfu.ca> <MATT.92Jul22142345@physics.berkeley.edu>

matt@physics.berkeley.edu (Matt Austern) writes:

>In article <1992Jul22.193837.18095@sfu.ca> palmer@sfu.ca (Leigh Palmer) writes:

>> "Mass" as you use it
>> is equal to neither inertial nor gravitational mass as those terms apply to
>> any system more complicated than a particle at rest!

>There is, however, *nothing* which is equal to either inertial or
>gravitational mass for a relativistic body.

>That is: I define the inertial mass of a body as the "m" appearing in
>the equation
>		F = m a,					(1)
[...]
>I believe that these definitions are customary; I don't know what
>other meaning could be attached to the phrases "inertial mass" or
>"gravitational mass."

Wellll, if you define F as dp/dt instead, and then define inertial
mass by the formula p = mv, then the total energy
(or "relativistic mass") *does* become exactly the "inertial mass."
But I still don't think this should be used in physics classes.

As for gravitational mass, I agree with you there: there really
isn't any such thing in the context of GR, unless you want to
define it trivially as the "inertial mass" defined above because
acceleration is independent of mass-- but that's hardly the
best way to look at it, though it's the language that often
gets used.

-- 
Matt McIrvin   mcirvin@husc.harvard.edu   Long live short .sigs
From: bweiner@ruhets.rutgers.edu (Benjamin Weiner)
Newsgroups: sci.physics
Subject: Re: Watch your language, Was: mind-numbing gedankenexperiment
Date: 27 Jul 92 19:46:31 GMT
Organization: Rutgers Univ., New Brunswick, N.J.

Paul Budnik writes:
> [criticism of my sloppy language on observables]
>Bell's inequality will never be violated in a universe in which events
>separated by space-like intervals never influence each other. Quantum
>mechanics implys the inequality is violated. It is not violated in a way
>that the influence is detectable *at the time it occurs* or in a way that
>allows a signal to be sent.  [ ... ]

Quite true; I should have said something about "controllables" or
something like that (language analogous to that in one of Bell's
essays, in his book).  There are many subtleties in this business,
like the Herbert photon-cloning which turned out to be incompatible
with the linearity of QM.  I guess the problem is that there are so
many proofs that FTL communication is impossible, that I am more
interested in the thought processes of the people that propose FTL
communicators than in their actual devices.  Closed-minded, ain't I?

Ben
From: macander@oasys.dt.navy.mil (Aleksander Macander)
Newsgroups: sci.physics
Subject: Re: density of commonly used materials
Date: 30 Jul 92 11:49:55 GMT
Reply-To: macander@oasys.dt.navy.mil (Aleksander Macander)
Followup-To: sci.physics
Distribution: usa
Organization: Carderock Division, NSWC, Bethesda, MD

In sci.materials, sundar@fiber-one.ai.mit.edu (Sundar Narasimhan) 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.
From: nadar@ece.arizona.edu (Mariappan S. Nadar)
Newsgroups: sci.physics
Subject: Renormalization Group
Date: 30 Jul 92 22:04:35 GMT
Reply-To: nadar@ece.arizona.edu (Mariappan S. Nadar)
Distribution: world,local
Organization: University of Arizona Dept. of Electrical and Computer Engineering

Hi:

	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.

	I am basically trying to understand the link between 
multiscale approach to image processing (using Gibbs distribution as
image models)
and renormalization group in statistical physics.


	Thanks in advance

	
							Mariappan S. Nadar

P.S. I hope I have posted the request to the correct newsgroup.
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 00:01:00 GMT

In article <24926@dog.ee.lbl.gov>, sichase@csa3.lbl.gov writes...
>What is classical in a cloud chamber (in which by the way, no one has ever
>seen a W!) is not the charged particle but the droplets which condense on the
>ionized nucleation sites.  The W itself is behaving quite nonclassically.

? 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?

Matt's post convinced me about the neutrino's though. You can't build
a classical field out of fermions.

So now I think the thing which makes the photon classically 'different' from
other particles is that it's a neutral boson. Like helium. Hmmm... 

Dave Ring
dwr2560@zeus.tamu.edu
From: jbaez@riesz.mit.edu (John C. Baez)
Newsgroups: sci.physics
Subject: Re: Work in process
Date: 22 Jul 92 16:05:55 GMT
Organization: MIT Department of Mathematics, Cambridge, MA

In article <711704651.F00001@therose.pdx.com> Bruce.Alexander@f255.n105.z1.therose.pdx.com (Bruce Alexander) writes:
>This is a plea for help.  I am writing a novel which will be infinitely more
>effective if I can discuss the details of time-space, magnetism and gravitic
>propulsion with someone who is informed on these subjects.
>
>I would prefer corresponding by netmail for obvious reasons. Someone respond,
>please!

Anyone who claims to be an expert on "gravitic propulsion" is a blatant
fraud, so you can filter out a bunch of folks that way.  Also, don't
trust anyone who says "time-space" instead of the more common
"space-time".
From: bweiner@ruhets.rutgers.edu (Benjamin Weiner)
Newsgroups: sci.physics
Subject: Re: Unprovable true statements (was Structure of Time)
Date: 29 Jul 92 23:56:45 GMT
Organization: Rutgers Univ., New Brunswick, N.J.

Dave Chaloux writes:
>Yaron Sheffer writes:
>>This one's easy: Truth is measureable in the lab, or observable in the
>>Universe, and in any case should be consistent and causal with anything
>>that we have ever observed/measured ...
>
>I was under the very definite impression that mathematicians have shown that
>the number of true statements is a larger order of infinity than the number of
>proofs and that therefore there are true statements that cannot be proved.
>If I am wrong, I'm sure this will be pointed out 8), but if true this should
>make one think twice about statements like the above.

If you're talking about incompleteness theorems, I'm not sure I would
phrase it the way you did, but it is in general true that with a finite
system of axioms there are statements which are true but cannot be
proved (thus the axioms are incomplete, hence the name).  

However, Yaron said that all true things ought to be
_consistent_ which is a far cry from being provable.  In fact a
statement inconsistent with your axioms is generally regarded as
"false"  (within that system of axioms that is).  There are not too
many true statements which are false.  In any case, what Godel-
theorems mean for something so logically lumpy as experimental
science isn't very clear.

Personally I rather doubt that "Truth is measurable in the lab,"
though, and have a little trouble with Truth-with-a-capital-T,
but maybe that just shows that I was never cut out to work on
quantum gravity.

Take with more salt then usual, I'm not a very good logician.
Ben Weiner
From: tvaughan@buphyk.bu.edu (Timothy Vaughan)
Newsgroups: sci.physics
Subject: Re: Blue Sky
Date: 23 Jul 92 13:53:23 GMT
Organization: Boston University, Physics Department

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! 

I'm not a biologist.  (I don't even play one on TV.)  I cannot comment
on the fact that there are blue birds.  However, I know that part of the
reason that flowers evolved to be so brightly colored (including blue)
is that the colors attract bees, which pollenate them.  In fact, some
flowers have patterns at infrared (or is it UV?) frequencies that bees
can see but we can't.

Tim
From: fanchiot@acf3.NYU.EDU (Sergio Fanchiotti)
Newsgroups: sci.physics
Subject: Re: Grad. Student Tax Rebate
Date: 30 Jul 92 02:29:00 GMT
Organization: New York University

/* acf3:sci.physics / U51773@uicvm.uic.edu (tom mckibben 2) / 12:55 pm  Jul 29, 1992 */
this is something I got wind of just a few days ago

To: All Graduate Students or Past Graduate Students (since 1986)

Subject: Bill in Congress - Federal Income Tax Exemptions

The US legislature is considering (or about to consider) a bill that would make
graduate student salaries exempt from federal income taxes. The bill would be
retroactive - ie. those students who have been paying taxes since 1986 could
file to receive a refund!! If you are interested in this bill, you should cont-
act your state's representative. Call 1-800-347-1997 for information about your
state's representatives, or call the House of Representatives directly at
 (202) 224-3121 for information. The number of the bill is: HR 4418 and was
introduced by Tom Lewis, a Representative from Florida.
-------------------------------------------------------------------------------

The letter above is dated July 8 and I got it one July 24 so if you would like
to help it pass there may not be too much time left. Please spread the word to
anyone who you think might be interested.

tom

thomas mckibben 2   university of illinois at chicago dept. of physics
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
BITNET: MCKIBBEN@UICPHY or U51773@UICVM
Internet: u51773@uicvm.uic.edu or tommck@aol.com
----------------------------------------------------------------------
Always state the obvious............................
/* ---------- */
Newsgroups: sci.physics
From: palmer@sfu.ca (Leigh Palmer)
Subject: Re: Converting the masses
Organization: Simon Fraser University
Date: Mon, 27 Jul 1992 19:05:51 GMT

In article <mcirvin.711903684@husc8> mcirvin@husc8.harvard.edu (Mcirvin)
writes:

>Wellll, if you define F as dp/dt instead, and then define inertial
>mass by the formula p = mv, then the total energy
>(or "relativistic mass") *does* become exactly the "inertial mass."
>But I still don't think this should be used in physics classes.

Then you adopt a different convention. My point is that using the
term "mass" in this way is not "wrong". It is currently unconventional.

Leigh
Newsgroups: sci.physics
From: dwr2560@zeus.tamu.edu (RING, DAVID WAYNE)
Subject: Re: Destroying the Earth
News-Software: VAX/VMS VNEWS 1.41    
Organization: Texas A&M University, Academic Computing Services
Date: Tue, 28 Jul 1992 07:00:00 GMT

matmcinn@nuscc.nus.sg (Mcinnes B T (Dr)) writes...
>To what radius would we have to compress the Earth in order to form a
>black hole? The Schwarzschild radius is usually cited, but that is
>rather strange, because the Schwarzschild radial coordinate does not
>measure distance. 

There are two issues here. One is at what radius will gravitation overcome
the repulsion of the exclusion principle, thus initiating catastrophic
collapse (dunno). The other is the ambiguity of 'radius'. I think by this
you have answered your own question, right? :)

Dave Ring
dwr2560@zeus.tamu.edu
From: jac@ds8.scri.fsu.edu (Jim Carr)
Newsgroups: sci.physics
Subject: Re: Defining Photons
Keywords: Relating photons E=MC^2 criticism
Date: 28 Jul 92 13:30:58 GMT
Reply-To: jac@ds8.scri.fsu.edu (Jim Carr)
Distribution: na
Organization: SCRI, Florida State University

In article <27JUL199219012221@zeus.tamu.edu> dwr2560@zeus.tamu.edu (RING, DAVID WAYNE) writes:
>In article <24926@dog.ee.lbl.gov>, sichase@csa3.lbl.gov writes...
>>What is classical in a cloud chamber (in which by the way, no one has ever
>>seen a W!) is not the charged particle but the droplets which condense on the
>>ionized nucleation sites.  The W itself is behaving quite nonclassically.
>
>? 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?

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.

(my page reference is to the Third Edition, part of the McGraw-Hill 
mustard-yellow book series, copyright 1968)

--
J. A. Carr                                    |  "The New Frontier of which I  
jac@gw.scri.fsu.edu                           |  speak is not a set of promises
Florida State University  B-186               |  -- it is a set of challenges."
Supercomputer Computations Research Institute |   John F. Kennedy (15 July 60)
From: alexa@hpnmdla.sr.hp.com (Alexander Anger)
Date: Thu, 23 Jul 1992 23:12:21 GMT
Subject: Re: The Future of Physics
Organization: Hewlett-Packard, Santa Rosa, CA