HDTenEightyP/NetNews huggingface dataset:
From: dk@imager (Dave Knapp)
Newsgroups: sci.physics
Subject: Re: Converting the masses
Date: 28 Jul 92 06:43:08 GMT
Organization: Laboratory for Experimental Astrophysics

In article <1992Jul27.191259.5549@sfu.ca> palmer@sfu.ca (Leigh Palmer) writes:
>In article <mcirvin.711904014@husc8> mcirvin@husc8.harvard.edu (Mcirvin)
>writes:
>>palmer@sfu.ca (Leigh Palmer) writes:
>>
>>Actually, neither definition of mass would be temperature-independent,
>>if you define it for the whole lump of coal.  When you raise the
>>temperature, the energy in the rest frame increases!  The sum of
>>the masses of all the particles is perhaps temperature-independent,
>>but as you complained before, that's not the mass of the lump.
>
>Exactly my point. The existence of an internal degree of freedom in a lump
>of coal which affects its mass vitiates the particle physicists' definition.
>Used outside particle physics this convention has no conspicuous advantages,
>and indeed it may lead to conceptual problems of its own.

   As I said before, what you present as the "particle physicists'
definition" is nothing of the sort.  It would be very helpful to the
discussion if you could not continue to promulgate this straw man.

   For example, the proton clearly has internal degrees of freedom that
affect its mass; the only difference is that the mass spectrum is discrete
and we give the various mass eigenstates individual names, so "proton" means
the N+ particle in its ground state.

   No such distinction, however, is made in the case of atoms; the mass of a
carbon atom, for example, depends not only upon the state of the nucleus, but
also of the atomic electrons.  In this case, however, we don't give every
excited state of the carbon atom a different name.  Even so, I think that every
particle physicist would agree that the mass of a carbon atom is its energy
in the rest frame.

   In other words, if you specify the state of your lump of coal sufficiently,
then the definition of mass is unambiguous.

   -- Dave

-- 
  *-------------------------------------------------------------*
  * David Knapp        dk@imager.llnl.gov       (510) 422-1023  *
  *            98.7% of all statistics are made up.             *
  *-------------------------------------------------------------*
Newsgroups: sci.physics
From: crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass)
Subject: Re: Space Station & APS
Keywords: infrastructure infrastructure infrastructure
Organization: University of Virginia
Date: Wed, 29 Jul 1992 17:58:16 GMT

In article <29JUL199213170451@stars.gsfc.nasa.gov> dc@cobi.gsfc.nasa.gov writes:
>There has been an active flame war here on the recent APS statement
>on the proposed Space Station, which I want to jump into right here.
>
>I have seen statements flying by that the APS opposes the Space Station.
>However, if you read the statement you can see that the APS only opposes
>the justification of SSF on the grounds of scientific research.
>Basically, the supporters of SSF told the public "This will be great for
>science" and the scientists have responded "It won't either".  The APS
>does not comment on other purported justifications of the SSF.

     Exactly.  However, if the APS is just concerned about the purity of 
     science, why do we not see large campaigns to eliminate quackery, a much
     more important misuse of scientific justifications?

     I believe that the answer lies in the real reason;
     a perceived funding competition between programs dear to the APS
     and SSF, for which there is little constituency in the APS.
     After all, they oppose *building* the space station, not
     just the use of science as a justification.

>Nor does the APS claim that no science will be done on the Space Station.
>Indeed, we only have to look at the history of the shuttle to forsee
>the future of space station science.  Experiments that would be better
>and more cheaply done in rocket-launched satellites will be forced to
>take a ride on the shuttle and get bolted to the Space Station.

     Exactly the reason that cost-efficiency should also be an
     objective of the space program.

                                   dale bass



--
C. R. Bass                                           crb7q@virginia.edu
Department of Mechanical and Aerospace Engineering
University of Virginia
Charlottesville, Virginia                            (804) 924-7926
From: throopw@sheol.UUCP (Wayne Throop)
Newsgroups: sci.physics
Subject: Re: Twins Paradox Resolved
Summary: direction has nothing to do with it
Date: 27 Jul 92 23:30:57 GMT

> From: metares@well.sf.ca.us (Tom Van Flandern)
> Message-ID: <BrrztE.J4u@well.sf.ca.us>
> In any frame, the apparent rate of progress of time (and distance) for
> a fast-moving traveler is quite different when the traveler is moving
> away, from what it is for an approaching traveler.  Naturally, neither
> the E-frame nor the T-frame runs systematically slower or faster than
> the other, since they are equivalent.  If we can agree on the
> resolution of the paradox, then perhaps we can go on to discuss its
> significance.

This is so clearly wrong that I suspect I'm missing Tom's point
altogether.  The "rate of progress of time (and distance)" of
a fast-moving traveler is identical whether "moving away" or
"approaching".  This is simple to see, because both are altered
by the factor of (1-v^2)^.5, which is always the same factor
regardless of the position of the traveler along a trajectory,
and regardless of the direction of motion along that trajectory.

It is true that neither the E-frame or the T-frame runs systematically
slower or faster.... they BOTH run slower or faster, depending on
who is measuring.

So, no, we (at least I) can't agree on a "resolution" of the "paradox"
that involves differing factors for approaching vs receeding objects.
--
Wayne Throop  ...!mcnc!dg-rtp!sheol!throopw
From: rsf1@RA.MSSTATE.EDU (Robert S. Fritzius)
Newsgroups: sci.physics
Subject: Re: Relativity
Date: 25 Jul 92 17:56:13 GMT


 
 
In article <1992Jul22.150401.15820@news.endg.convex.com> Steve Warren
writes:
 
>. . .
>...When particles get zinging around near c in, say, the Bevatron
>here at Berkeley, not only does it require more enery to accelertate
>them, but when they smash into something (...) the energy released
>is significantly *more* than can be accounted for by the particles
>rest mass...
 
 
In article <1992Jul24.230350.16042@murdoch.acc.Virginia.EDU> Cameron
Bass responds:
 
>>One could always say that the field merrily trails along with the
>>particle and carries the energy. ...
 
If we set aside Ritz's (1908) assertion that his emission particles obey
Galilean relativity, and have them traveling at the speed of light, say
with respect to the Bevatron, then the emission particle fluxes should
compress (in Doppler-like fashion) in the forward direction of Bevatron
passengers and constitute shock-wave like electrodynamic hammers.
 
How do we (un-ambiguously) differentiate between energy released by a
hypothetical "electrodynamic hammer" such as in the previous paragraph
(or the energy trailing along in the field, according to Bass) and the
effects of a relativistically increased mass smashing into things.
 
 
>>... A bigger problem, though, is explaining other things like the
>>apparently physical time dilation experienced by things like mesons.
 
In nuclear fission, fast neutrons need to be slowed way down to thermal
speeds to increase the likelihood of their entering into neutron capture
events.  It's as though there is a minimum value of neutron dwell-time in
close proximity to a nucleus required to enable the capture.
 
Perhaps for mesons there is a velocity related dwell-time factor
at work in their decay mechanism in addition to (or rather than) a
time-dilation effect.
 
 
>>. . .
>>It is interesting that, Pauli's assertions notwithstanding, it was
>>not until the 60's that there was good evidence that Ritz's theory
>>was not really tenable.  The relevant measurements involve direct
>>time of flight experiments with things like gamma rays with huge
>>extinction distances emitted from fast-moving pions (...) seem to
>>indicate beyond reasonable doubt that light does not travel at c
>>with respect to the source. ...
 
One possible problem with these types of experiments is that we have
not had measurements (inside the target material) of the actual velocity
of the pions at the times they emitted the gamma rays.
 
--------------------------------------------------------------------------
 
 
             Robert S. (Bob) Fritzius  rsf1@ra.msstate.edu
                   I have a slobber-proof keyboard!
      Low-Tec  P.O. Box 1327 Starkville, MS 39759   (601) 324-1284
 
Newsgroups: sci.physics
From: jbaez@riesz.mit.edu (John C. Baez)
Subject: Re: ... an infinite mesh of 1ohm resistors ...
Organization: MIT Department of Mathematics, Cambridge, MA
Date: Tue, 28 Jul 92 14:14:07 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 <1992Jul28.000844.27051@mixcom.com> ttyytt@mixcom.com (Adam Costello) writes:
>In article <1992Jul27.210947.5820@fs7.ece.cmu.edu> snyder@henry.ece.cmu.edu (John Snyder) writes:
>>
>>I believe that you are missing the point of the previous post here.
>
>But I think you are missing the point of the second post.  The "solution"
>involved imagining that you could inject an amp of current into a network
>of resistors.  No capacitors!  Where is the charge supposed to go?
>Regardless of whether this can be done in the laboratory, there's still
>the question of whether it can be done in the mind.  Certainly, if the
>network were finite, it would make no sense.  Does the infinitude of the
>network allow a source with no sink?  We can argue that it does this way:

Yes, an infinite network is necessary and sufficient to have a source
but no sink.  The charge goes "off to infinity".  This isn't as weird as
one may think.  Look at the equation of electrostatics div E = rho.
In a closed universe (e.g. a three-sphere) this implies (with Gauss's
theorem) that the total charge in the universe must be zero because
there's "nowhere for the electric field lines to go".  However in an
infinite universe one can have nonzero total charge.  

That example may have made it seem more rather than less weird.  But
mathematically they are very analogous.  

The fact that one can only do this trick for an infinite network doesn't
mena that the answer is very far off for a big finite network.  One
could grunge through the problem on a big finite network (hopefully with
aid of a computer) and see, hopefully, that the answer provided by the
slick trick was very close.  

John Baez
From: jac@ds8.scri.fsu.edu (Jim Carr)
Newsgroups: sci.physics
Subject: Re: Relativity
Date: 25 Jul 92 22:06:30 GMT
Reply-To: jac@ds8.scri.fsu.edu (Jim Carr)
Organization: SCRI, Florida State University

In article <9207251756.AA07822@Ra.MsState.Edu> rsf1@RA.MSSTATE.EDU (Robert S. Fritzius) writes:
>
>In article <1992Jul22.150401.15820@news.endg.convex.com> Steve Warren
>writes:
> 
>>...When particles get zinging around near c in, say, the Bevatron
>>here at Berkeley, not only does it require more enery to accelertate
>>them, but when they smash into something (...) the energy released
>>is significantly *more* than can be accounted for by the particles
>>rest mass...

More importantly, the momentum (hence the magnetic field required to 
bend the beam) is seen to increase even though the speed does not.

>In article <1992Jul24.230350.16042@murdoch.acc.Virginia.EDU> Cameron
>Bass responds:
> 
>>>... A bigger problem, though, is explaining other things like the
>>>apparently physical time dilation experienced by things like mesons.
> 
>In nuclear fission, fast neutrons need to be slowed way down to thermal
>speeds to increase the likelihood of their entering into neutron capture
>events.  It's as though there is a minimum value of neutron dwell-time in
>close proximity to a nucleus required to enable the capture.

This is not correct.  Slow neutrons are needed only for the fission of 
specific nuclei such a U-235.  Fast neutrons are required for the 
fission of other nuclei, such as U-238.  The optimum energy is dictated 
by nuclear-structure details such as the location of resonances (states 
of target+neutron that are unbound but act as if they are -- and can 
sometimes be coupled strongly to the ground state or an isomeric state 
that leads to spontaneous fission).  These resonances have been very 
carefully mapped out and tabulated in terms of parameters and graphs. 

>Perhaps for mesons there is a velocity related dwell-time factor
>at work in their decay mechanism in addition to (or rather than) a
>time-dilation effect.

It would be rather curious to see how you would get *exactly* the 
non-linear relationship predicted by relativity and observed in 
experiment, in particular the same factor as one gets for the mass...

--
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)
Newsgroups: sci.physics
From: kck+@cs.cmu.edu (Karl Kluge)
Subject: Intelligent Vehicles
Date: Fri, 24 Jul 92 02:31:28 GMT
Organization: School of Computer Science, Carnegie Mellon

This discussion seems to have gotten embedded in sci.physics, although I
suspect there must be a more appropriate venue elsewhere on the net. The
proceedings of Intelligent Vehicles '92 (sponsored by IEEE Industrial
Electronics Society, co-sponsored by SAE and some other folks) contains a
representative sampling of what is going on. The book VISION-BASED VEHICLE
GUIDANCE (edited by Ichiro Masaki) also contains a good selection of papers.

The reliability requirements for autonomous road following are daunting --
the mean time between fatal accidents is approx. 1 million vehicle-hours.
For a vision based system running at 10 Hz, that translates into an average
of 36,000,000,000 images processed without making a sufficiently serious
error to cause a fatality.  The California PATH people have been looking at
plopping ceramic permanent magnets into the pavement to mark the lane center
and tracking those.  

Which of the competing approaches "wins" from the point of view of
non-technical considerations is unclear. The Feb '91 IEEE Transactions on
Vehicular Technology contains a number of good papers discussing policy
issues, and pointing off to references evaluating palletization vs.
entrainment vs. platooning vs. uniform spacing at moderate headways.
From: andrew@rentec.com (Andrew Mullhaupt)
Newsgroups: sci.physics
Subject: Re: The It from Bit: Quantum Logic and Information Theory
Date: 21 Jul 92 02:31:07 GMT
Organization: Renaissance Technologies Corp., Setauket, NY.

In article <54526@mentor.cc.purdue.edu> hrubin@pop.stat.purdue.edu (Herman Rubin) writes:
>There have been many attempts to describe quantum mechanics within 
>probability, but I know of no successful ones.  Quantum processes
>are far more complicated than stochastic processes.

I don't get it. Aren't path integral formulations essentially probabalistic
in nature? 

Also, what about Ed Nelson's stochastic mechanics? I heard a long time ago
that Stoch. Mech. made some scattering predictions at variance with QM,
and that experiments were going to be done. Is this true? On the other
hand, I was given to understand that one had to go quite a long way to
get at these deviations from QM.

Later,
Andrew Mullhaupt
From: jonathan@cs.yorku.ca (Jonathan Ostroff)
Newsgroups: sci.physics
Subject: Mirror reflections - quantum theory of light
Keywords: mirrors, reflection of light, photons
Date: 26 Jul 92 18:58:03 GMT
Article-I.D.: yetti.1365

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. This may be because of what happens when
the photons hit the mirror. For example, do the photons collide with
mirror atoms and become absorbed into these atoms. These excited atoms
then perhaps give off new photons that reflect back to form the image.
Or perhaps there is some other exchange mechanism that takes place at
the mirror surface. What percentage of the original photons reflect
back to form the image.

When I looked this up in my undergrad textbooks I was told that in
issues such as reflection and refraction light must be treated as
having a wave nature. So, perhaps the above question is not properly
formulated. 

I would very much appreciate any opinions on this, especially if there
are standard reference works that I can consult.

-- 
Jonathan Ostroff

Dep. of Computer Science,
York University,
From: bhoughto@sedona.intel.com (Blair P. Houghton)
Newsgroups: sci.physics
Subject: Re: Gyromagnetic ratio of the proton
Date: 28 Jul 92 17:03:23 GMT
Distribution: na
Organization: Intel Corp., Chandler, Arizona

In article <1992Jul27.204759.26632@murdoch.acc.Virginia.EDU> crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass) writes:
>In article <24945@dog.ee.lbl.gov> sichase@csa2.lbl.gov writes:
>>75% of everything interesting in the universe can be found in the little
>>pocket version of that book.  90% can be found in the larger, full listings.
>>An additional 5% is in "Inside Macintosh."   The last 5% is spread 
>>pretty thinly... :-) 

<Mumble something here about background radiation>

>     It also does not appear to be inside the Macintosh downstairs
>     (we had all the protons removed during the last maintenence).
>     By the way, does anyone know how to put it back together ...

Piece o' cake, except for the 10-day lead-time for UPS
to ship the 17-inch torx-head screwdriver, all you need
to do is double-click on the appropriate icon...

				--Blair
				  "Talk about yer orthogonal toolkits..."
From: Bruce.Alexander@f255.n105.z1.therose.pdx.com (Bruce Alexander)
Sender: postmaster@therose.pdx.com
Newsgroups: sci.physics
Subject: Work in process
Date: Tue, 21 Jul 1992 17:29:00 -0700

This is a plea for help.  I am writing a novel which will be infinately 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!

                                        bca

Newsgroups: sci.physics
From: matmcinn@nuscc.nus.sg (Mcinnes B T (Dr))
Subject: Re: Destroying the Earth
Organization: National University of Singapore
Date: Thu, 30 Jul 1992 04:44:27 GMT

Hmmm.... I'm not getting very specific answers here...aren't you people
worried that the answer might turn out to be around 6 or 7 thousand
kilometres or so? 
Newsgroups: sci.physics
From: gast@next.ben-fh.tuwien.ac.at (Gast)
Subject: Re: magnetic insulators and shape-memory alloys (was Re: PZT Excitation)
Organization: Technical University of Vienna
Date: Tue, 28 Jul 1992 08:44:24 GMT

In article <1992Jul27.192208.22936@menudo.uh.edu> mece1xg@menudo.uh.edu  
(purna) writes:
> In article <1992Jul27.185909.19949@pbhyg.PacBell.COM>  
rhsomer@PacBell.COM (Bob Somers) writes:
> > Is there any material that acts as an insulator
> >from magnetic forces?  I was told some time ago
> >that there is none, but perhaps some new material
> >will do this.

Hello out there, here is my contribution:

An ideal magnetic insulator is an ideal paramagnet (susceptibility of  
one). That means every magnetic field is pulled out of the material.

Superconductors are ideal paramagnets, the phenomenia of magnetic flux  
pulled out of the material is called Meissner-Oxenfeld-effect.

Hope I could help

--
Harald Lakatha                : Pleas add to subject:
gast@next.ben-fh.tuwien.ac.at : an Harald - nicht loeschen
From: macander@oasys.dt.navy.mil (Aleksander Macander)
Newsgroups: sci.physics
Subject: Re: density of commonly used materials
Date: 30 Jul 92 12:04:18 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.

Hi Sundar,
Sorry for the previously posted blank. Simple screw up! However in response
toyour question. An excellent source or reference book that has physical
data (densities, constants etc.) on commonly used materials is
MARKS' STANDARD HANDBOOK FOR MECHANICAL ENGINEERS by Baumeister et al.
(McGrawaw Hill Publisher).  This should be readily available in your
MIT library.  There are also numerous other similar sources with this
information.
Lots of luck, Alex
Newsgroups: sci.physics
From: tenney@med.unc.edu (Charles R. Tenney)
Subject: Helium Ballons in a Car (was Re: Air bubbles in a universe of water)
Organization: UNC-CH School of Medicine
Date: Wed, 22 Jul 1992 04:16:55 GMT

In article <1992Jul15.202609.23833@galois.mit.edu> jbaez@taylor.mit.edu (John C. Baez) writes:
>In article <91075@bu.edu> tvaughan@buphyk.bu.edu (Timothy Vaughan) writes:

[discussion of water bubbles deleted]
>The following chestnut, which has already been discussed here, is
>related.  Say you have a helium balloon in a car and you suddenly stop.
>Does it move towards the front of the car (like you) or to the back?

Yes, toward the back as the air (higher density air than the helium)
tries to slam up against the windshield, pushing the helium balloon out of
its way as it does so.  Under acceleration, the balloon goes towards the
front.

One of my old physics Professors, Robert Romer at Amherst College, told
our mechanics class about how he actually tried this, and showed his
child/ren (I don't recall how many) how it worked that way, braking and
accelerating, with the balloon behaving as described above.  As he turned
onto his street going home, he heard an "Oh my God!" from the back seat as
the balloon was observed leaning toward the INSIDE of the turn.  He hadn't
anticipated that one, but it's obvious in hindsight.

balloon doing the above behavior.  


-- 
--
Charles R. Tenney	tenney@med.unc.edu   | What would the UNC school of
					     | Medicine want with my opinions?
	"My karma ran over my dogma."	     | What would I want with theirs?