HDTenEightyP/NetNews huggingface dataset:
From: Richard.Mathews@West.Sun.COM (Richard M. Mathews)
Newsgroups: sci.physics
Subject: Re: New group/groups : Branching of sci.physics
Date: 15 Oct 1992 01:44:24 GMT
Organization: Sunsoft Inc., Los Angeles, CA.
NNTP-Posting-Host: astro
Originator: richard@astro.West.Sun.COM

I'd like to put in a word against a split.  The traffic here is high
enough to possibly justify a split, but the problem is that too many
of the topics discussed cross over between many branches of physics.
Relativity and quantum mechanics is a very common combination, for
example.  If everyone solves this by cross-posting, then all we have
done is created a larger number of groups with too many postings in
each of them.

Then consider what sort of articles would go into any one of these groups.
Let's try s.p.quantum.  There would be the descriptions of theories such
as tangles and strings, etc.  There would be the occasion discussion of
new experimental results.  There would be the flame wars on quantum
collapse, many worlds, etc.  And then there would be the articles with
high crackpot index trying to throw out everything.  What we we have
accomplished by the split?  Would any of these groups really be more
readable that sci.physics is now?  Or would we just have a large number
of groups each of which has a mixture of good stuff and crap (for whatever
definition of good stuff and crap any particular person may choose).

I stay stick with kill files.  If you don't think that your news reader
does a good enough job of helping you filter out the crap, I'll bet you
could find another reader more to your liking.

     Richard M. Mathews			F oster 
					 E stonian-Latvian-Lithuanian
Richard.Mathews@West.Sun.COM		  I ndependence and
					   F reedom!
Newsgroups: sci.physics
From: daryl@oracorp.com (Daryl McCullough)
Subject: Re: Quantum Zeno Effect, Part 1.
Organization: ORA Corporation
Date: Fri, 9 Oct 1992 01:27:27 GMT

In article <5992@dove.nist.gov>,
gilligan@bldrdoc.gov (Jonathan M. Gilligan) writes:

>In fact, the quantum Zeno paradox (the inhibition of spontaneous decay
>by frequent measurement) does not occur in spontaneous decay (such as
>radioactive decay of nuclei) so long as the decay is exponential.
>Here is a proof:
>
>  Start with the particle in an unstable state |\psi_0> with lifetime \tau.
>
>  The probability that after 
>  time t, the particle has
>  not decayed is:               P(t) = exp(-t/\tau)
>
>  Peek N times between 0
>  and t. Now the probability
>  that the particle has not 
>  decayed is:                   P_N(t) = (exp(-t/N \tau)^N = exp(-t/\tau)
>                                independent of N.
>
>Thus, the quantum Zeno paradox (inhibited spontaneous decay) occurs
>_only_ if decay is nonexponential at short times (nonexponential decay
>is predicted by theory, but has never been oberved). A good paper by
>Ghirardi, Omero, Weber, and Rimini (Nuovo Cimento 52A, 421 (1979))
>shows the difficulty (impossibility) of detecting this phenomenon
>using practical detectors.

I don't consider exponential decay to be a counter-example of the
Zeno, but a consequence of it! Rather than deal with nuclear decay,
let me try a simpler problem: A spin-1/2 particle starts off in the
state |+1/2> (spin in the z-direction is +1/2) with a magnetice field
in the y-direction. Now, because |+1/2> is not an energy eigenstate,
it will tend to evolve into a superposition of |+1/2> and |-1/2>.
Actually, in this case the evolution is exactly solvable:

    |Psi(t)> = cos(omega t) |+1/2> + sin(omega t) |-1/2>

where omega = mu B/h-bar, B is the strength of the magnetic field,
and mu is the magnetic moment of the particle.

So when there is no observation, there is a sinusoidal variation of
the spin direction with time, going from |+1/2> at time 0 to |-1/2>
at time pi/(2 omega).

Now we will consider an experiment in which the z-component of the
spin of the particle is continually observed at intervals dt such that
1/dt is much greater than omega. The experiment ends when spin -1/2 is
observed.

The probability after N observations that the particle will still be
found in the state |+1/2> every time is approximately exp(-a N dt^2),
where a = (mu B/h-bar)^2. Letting T = N dt be the total time, we get
the probability as

     exp(-T/\tau)

where \tau is a time constant given by 1/(dt (mu B/h-bar)^2).

In other words, the Zeno effect *leads* to exponential decay of
states!

Now, I'm not saying that exponential decay is always caused by the
Zeno effect (in particular, I don't think you can explain radioactive
decay in terms of it), but it certainly doesn't contradict the
predictions of the Zeno effect. (Note that the Zeno effect for my
example only shows exponential decay for times T that are large
compared with the time constant \tau.)

Daryl McCullough
ORA Corp.
Ithaca, NY
Newsgroups: sci.physics
From: dproctor@lspd.jsc.nasa.gov (david r. proctor)
Subject: Re: motions of astronouts
Followup-To: sci.physics,sci.space,sci.space.shuttle
Organization: NASA/Johnson Space Center/SE3
Date: Fri, 16 Oct 1992 15:19:46 GMT

In article <92286.151341A10630@TRMETU.BITNET>, enis tuncer
<A10630@TRMETU.BITNET> wrote:
> 
> Hi,
> 
> I have two questions,
> 
> 1. I know that the suits that astronouts wear are not suitable for them to move
>  quickly, forget about their suit. How their reflexes change in space(not in sp
> ace shuttle because in space shuttle there is air)? do they move faster? And th
> e effect of gravity on human motion?
> 
> 2. Astronouts don't use their balance systems, what kinds of problems do they h
> ave when they came to earth?
> 
> THANX.
> 
> Enis TUNCER
> M.E.T.U.
> PHYSICS DEP.
> A10630 at trmetu

1. The reflex action of astronauts in the zero-g envirnonment has been
studied for some time. The data that i've seen seems to indicate that they
do not
really move faster. This is based upon recording the EMG (electromyogram)
of a muscle after have been excited by an electrical stimulus. The speed by
which the nerve conducts the electrical current to the muscle is measured
by a change in the EMG recording which usually results in a muscle twitch.
In zero-g, there appears to be some latency of nerve conduction compared to
the one-g on earth, which might indicate a slower movement. I have not
heard of any complaints by crews of this effect.

2. One of the reasons that balance is affected is because there is a change
in the vestibular system of the crewman. The vestibular system is composed
of the interelationships between the eyes, inner ear, and the nervous
system. On ascent the system begins to adapt the zero-g since the fliud in
the inner ear now longer acts like a gravity or postion indicator for the
rest of the body. There is a disconnect so to speak between the information
from the eyes, the inner ear, and the loss of contact points (nerve sensors
in the ankles primarily). What results is something that is called Space
Adaptation Syndrome or SAS. Some crewmen experience nausea, disorientation,
loss of depth perception and so on during the first few days in orbit. The
system usually "rights" itself after these first few days and no problems
are experienced. When the person returns to earth however, the exact
opposite occurs. The inner ear begins to act like a gravity sensor and the
system must readapt to one-g. This causes some balance loss and the same
sort of effects as seen during the first few days in orbit.

If you want further information you might look for papers describing
scientific findings during STS-40 (SLS-1) and STS-42 (IML-1).
Newsgroups: sci.physics
From: jbaez@riesz.mit.edu (John C. Baez)
Subject: Re: Spontaneous Symmetry Breaking
Organization: MIT Department of Mathematics, Cambridge, MA
Date: Wed, 7 Oct 92 02:16:58 GMT

In article <1992Oct6.183626.24921@mnemosyne.cs.du.edu> aankrom@nyx.cs.du.edu (Anthony Ankrom) writes:
>
> I have never read this group so I have no idea if it has been sloshed
>around before, butI would like to know, in a nutshell, just what
>Spontaneous SymmetryBreaking is. I read an article in a quantum chemistry
>journal that discussed SSB in the visual cortex in relationship to viual
>hallucinations. (I can provide a reference if it would be handy. I have
>studied verylitlle quantum mechanics, but feel free to use technical
>terms...) This would put an interesting perspective on my study of
>neurology.

Hi; I'll try to explain spontaneous symmetry breaking and then I'll
venture a guess as to its applications to visual hallucinations.

Say you have a pencil standing perfectly vertically on its sharpened
point.  The slightest disturbance will make it fall over, and due to the
uncertainty principle quantum mechanics says it will fall over even if
there is NO disturbance.  It doesn't have any preference for falling
over in one direction or the other, but it will fall over in SOME
direction.  That's the "spontaneous symmetry breaking."  There is a
rotational symmetry to the original situation that will be broken when
the pencil "picks" a direction to fall in.  

Other examples: if you heat up a block of iron above a certain
temperature called the Curie point it will demagnetize.  When you cool
it back down it will spontaneously magnetize, randomly "choosing" one
axis as the north pole.  Ditto for water crystallizing into ice,
although here it is the crystal lattice which breaks the rotational
and translation symmetry of the liquid water.  

To get more biological, it is likely that the preference of biomolecules
to have one rather than the other handedness is a case of spontaneous
breaking of right/left symmetry.  This is debated, however.

For hallucinations, I can imagine this.  A subject looks at a
featureless wall and his visual field is roughly rotation and
translation symmetric (of course it has a finite size so translation
symmetry is only locally true).  If he is given a drug that encourages
visual hallucinations we can imagine his neurons being "ready" to fire
in all sorts of patterns, like the pencil is ready to fall, and the
slightest disturbance will make them fire and make him see patterns that
break the symmetry of the visual field.
From: davep@paladin.corp.sgi.com (David Packer)
Newsgroups: sci.physics
Subject: Re: SALE: neutron generator
Date: 16 Oct 92 17:24:08 GMT
Organization: Silicon Graphics, Inc.  Mountain View, CA
NNTP-Posting-Host: paladin.corp.sgi.com


I thought it was illegal to use the Internet for
Commercial advertising!!


Dave Packer

---
Newsgroups: sci.physics,sci.astro,sci.math,sci.philosophy.tech
From: mei172@cch.coventry.ac.uk (guru)
Subject: Re: STRUCTURE OF TIME
Organization: Coventry University
Date: Tue, 6 Oct 1992 15:28:20 GMT

In article <1992Oct02.130413.22524@dlogics.com> trr@dlogics.com (Tim Ringwood) writes:
>
>Two views on these wonderful post that are feeled with such love. NOT!
>
>1. One who feel they must spout of their belief in a place where it
>   does not belong, (this is MATH not RELIGION) is either arrogant or
>   a fool.

guru sez:
	naaah, they're usually people who've been trapped by a belief-system
	that *insists* on crusading and spreading the word. A little humility
	and a sense of humour helps to avoid getting really peeved at them.. 


>2.  I strongly feel that those who belive in God due so because of 
>    their own insecurity to deal with life as it is.  (Kind of link
>    a lonley kid's pretend friend. ) If you need help with your insecurities 
>    go to a shrink, and stop cluttering up this news group.

	Maybe that was the original reason, but to ignore the effect of
	familial belief patterns (church-going, prayer, funerals etc) is
	just plain daft. If you need help with your insecurities, you 
	are a pretty poor sort of person. Also the above ignores the tremendous
	solace many people get from their religion in stressfull situations,
	where the rest of us have to think harder.

>3.  I am not sure what TIME and MATH has to do with each other, i.e I 
>    can't see out MATH can help define the structure of time.  If somebody
>    out there has a REAL idea about this, please post.

	If *anybody* has a method of describing the structure of spacetime
	*without* involving mathematics, please let the rest of the world 
	know about it. Time is something which can only be defined in terms
	of movements through the spacetime continuum, and maths is the best
	way we have to do that at the moment.

-- 
      /~~~) /   / /~~~) /   /  
     (___/ (___/ /     (___/   These mind-expanding drugs have given me so much
        /                      imagination, I'm hallucinating grey vividly....
   (___/ mei172@cch.cov.ac.uk                       Victor Lewis-Smith
From: platt@watson.ibm.com (Daniel E. Platt)
Newsgroups: sci.physics
Subject: Re: Einstein's energy equation
Date: 16 Oct 92 18:43:13 GMT
Organization: IBM T.J. Watson Research Center
Disclaimer: This posting represents the poster's views, not necessarily those of IBM

In article <m8uosB2w165w@1776.COM>, bob@1776.COM (Robert Coe) writes:
|> Can someone send me (or point me to) a derivation of Einstein's equation
|> E = mc**2?  (When I try to derive it, I always seem to come up with
|> (mc**2)/2.)  :^(    adTHANKSvance...........

This is messy...

	d\tau^2 = dt^2 - dx^2 / c^2.

	{{d\tau} \over {dt}} = \sqrt{1 - {{v^2} \over {c^2}}} = 1 / \gamma.

	\Delta E = \int {{d \vec p} \over {d t}} \cdot d \vec x

	where
		\vec p = m {{d \vec x} \over {d \tau}}.
			= m \gamma {{d \vec x} \over {d t}} 
			= m \gamma \vec v.

	Then

	\Delta E = {1 \over m} \int \vec p \cdot {{d \vec p} \over {d t}} d \tau

	or
	\Delta E = {1 \over m} \int \vec p \cdot {{d \vec p} \over {d \tau}} \gamma
		d \tau.

The problem is that extra factor of \gamma.  Its better to take this apart
from a different direction.

Another way to derive it that's much easier is as follows:

	d \tau^2 = dt^2 - dx^2 / c^2.

Then, multiplying through by m^2 c^4, and 'dividing' by {d \tau}^2

	m^2 c^4 = m^2 c^4{{dt}\over{d\tau}}^2 - p^2 c^2
		= m^2 c^4 \gamma^2 - p^2 c^2.


Identifying
		E = m c^2 \gamma,

This becomes

	m^2 c^4 = E^2 - p^2 c^2.

Then,

	0 = EdE - c^2 \vec p \cdot d \vec p
	   = m c^2 \gamma dE - c^2 m \gamma \vec v \cdot d \vec p.

The gamma's divide out.  d \vec p = {{d \vec p} \over {d t}} dt.  
and lastly, \vec v dt = d \vec x.  Then

	dE = {{d \vec p} \over {dt}} \cdot d \vec x,

which was to be shown.  It also shows that 

	m^2 c^4 = E^2 - p^2 c^2 

depends directly on the structure of space time, and that (E/c, \vec p) forms a
covariant 4-vector.  That is, something with rest momentum-energy (E_0/c, \vec 0)
in one reference frame will have a momentum energy (E/c, \vec p) in another
frame which is related to the first by a Lorentz transformation.  Its all tied
together.

Hope this helps...

Dan
 
-------------------------------------------------------------------------------
Daniel E. Platt                                      platt@watson.ibm.com
The views expressed here do not necessarily reflect those of my employer.
-------------------------------------------------------------------------------
From: dbc@ecs.soton.ac.uk (Bryan Carpenter)
Newsgroups: sci.physics
Subject: Re: Transporter Technology
Date: 16 Oct 92 13:19:29 GMT

In <1992Oct11.062259.23675@mnemosyne.cs.du.edu> ddixon@nyx.cs.du.edu (David Dixon) writes:

>In article <1b79amINN8cl@usenet.INS.CWRU.Edu> bz223@cleveland.Freenet.Edu (Danny Guy Frezza) writes:
>>
>>This may sound far out, but does anyone have any information on current
>>research in Transporter Technology, ie, the technology used on Star Trek?
>>It seems to me, that if the law of physics holds, ie, "matter cannot neither
>>be created nor destroyed, but transformed into energy of another form", that
>>this technology, although far out, is not impossible.
>>Please email if anyone has any current research on this topic or knows of it.
>>-- Thanks!
>>-- 
>>
>>Dan Frezza
>>Internet: bz223@cleveland.Freenet.Edu
>>
>Gee, it sounds so neat, too.  While you are correct about matter/energy
>being neither destroyed nor created, you have neglected that to regenerate
>a human being, you have to know how to organize this matter/energy so as not
>to wind up with Jello.  Given the complexity of even an inanimate object
>like a rock, it would seem that a truly tremendous computer would be required
>to reconstruct you or me.

>This is not to rule out the technology, just to say that it probably doesn't
>exist now.

Oh... Stick your neck out.  99.999% certainty it will never exist!

>					Dave

Bryan
Newsgroups: sci.physics,sci.astro,sci.math,sci.philosophy.tech
From: mhosea@seas.smu.edu (Mike Hosea)
Subject: Re: STRUCTURE OF TIME -- interpretation?
Organization: SMU School Of Engineering and Applied Science
Date: Sun, 11 Oct 1992 05:29:58 GMT

In article <1992Oct10.215124.12144@aee.aee.com> gene@aee.aee.com (Gene Kochanowsky) writes:
>	Surely there must be another forum on net news for this sort of thing.
>	There are many people here trying to do science. You "Don't confuse
>	me with facts, I know my religion" types, GO ELSEWERE PLEASE! As for
>	the poor fellow above, either get a religion, or give up science,
>	but GO ELSWHERE!

My apologies.  I'm afraid I hadn't noticed that the orginals I followed up on 
were cross-posted.
-- 
Regards,
Mike Hosea (mhosea@seas.smu.edu)
From: mlevin@husc8.harvard.edu (Michael Levin)
Newsgroups: sci.physics
Subject: a question about water waves
Date: 14 Oct 92 23:58:17 GMT
Article-I.D.: husc3.1992Oct14.195818.16396
Distribution: usa
Organization: Harvard University Science Center


      I have a question about waves. I was thinking about water waves,
but maybe this has interesting applications in electromagnetic waves,
etc. Here goes - sorry if it is a stupid one.
     When an ideal wave moves across a surface of water, each
individual water molecule moves only up and down - not laterally; thus
it is the pattern of which point is highest that moves in the
"direction of the wave", not any individual water molecule (am I right
on all of this?).  My question is, suppose you freeze-frame a water
wave that was mving due north at some point. You now have a peak,
which during the next frame(s) will go down, and the next north-most
patch of water will then move up. What exactly is it that determines
that the next patch of water to move up is that north (i.e., in the
direction that the wave was moving) of the previous peak? After all,
looking at a frozen frame of a water wave, can you tell which way it
was moving? It seems that there is a symmetry of what the water can do
after any initial moment in time, and if so, where does the
directionality of the wave's motion come from?
    Does this make any sense or have I confused myself with poor
intuition and a zeno-like paradox? Please reply to
mlevin@husc8.harvard.edu.

Mike Levin
From: bweiner@ruhets.rutgers.edu (Benjamin Weiner)
Newsgroups: sci.physics
Subject: Re: Schrodingers Dog
Date: 9 Oct 92 01:46:45 GMT
Organization: Rutgers Univ., New Brunswick, N.J.


 naturman@uctvax.uct.ac.za writes:
>You are assuming non-determinism, a rather shakey philosophical idea. If I am
>not mistaken, non-deterministic non-hidden variable interpretations result
>in subjective reality paradoxes.

1.  Non-determinism is not a shaky philosophical idea.  Or did I miss
the World Conference of Philosophers' announcement that determinism
is now accepted to be true by all philosophers?  

2.  You're mistaken.

OK, I'll amplify.  When you say "subjective reality paradoxes," I
assume you mean EPR-style "paradoxes," which maybe should be called
"objective reality paradoxes" since the QM prediction is in conflict
with objective (local) realism, modulo Paul Budnik.  Another way of
thinking about this is to believe that quantum mechanics as a 
non-deterministic non-hidden variable theory is right and strict
objective realism is wrong.

In other words, maybe objective realism is the shaky philosophical
idea.
Newsgroups: sci.physics,sci.math,soc.men,soc.women
From: cgates@mitre.org (Curt Gates)
Subject: Re: Mattel on women
Organization: The MITRE Corporation
Date: Wed, 14 Oct 1992 13:08:31 GMT

In article <1992Oct12.173039.3065@tellab5.tellabs.com> chrz@tellabs.com 
(Peter Chrzanowski) writes:
>  I agree that the quality of science reporting, or even technology 
>  reporting, in newspapers is unbelievably bad, to the point where most, not >  some, stories have at least one "howler" in them.  
>  If political reporters were as bad as science reporters they'd confuse
>  events in Moscow, Kansas with events in Moscow, CIS.

Maybe when the sources of science information become articulate enough to 
express themselves effectively, science reporters wont have to guess at 
what their sources are trying to say.  If people in science and technology 
were more articulate, the growing numbers of tech writers would have to 
find a new way to make a living.

>  In fairness, it might be noted that a lot of 20th century science is 
>  either counter-intuitive, or just difficult to understand.

Worse, science and technology have become corporate, rather than 
individual.  In the 19th and early 20th century, there was a belief that a 
person of limited finances, and working alone, could make worthwhile 
discoveries, and even get rich in the process. And there was a lot of 
truth to that.  You can find that belief in 19th century copies to 
Scientific American through early 20th century copies of Popular Science 
and Popular Mechanics.  Even the Scientific American of the 1950s had a 
great column called the Amateur Scientist.

What this has to do with Barbie is that these publications tended to 
describe science and technology as a male domain, often closely connected 
with the military.  If you want a real chill, look through some 1950s 
issues of MIT s Technology Review.

Also associated with science and technology, and reaching a peak in the 
50s, was an attitude of intellectual elitism and a desire to *exclude* 
popular understanding.  This elitism still exists, particularly in places 
of higher education, which loops back to an observation I made earlier 
about intellecutal elitism having an effect similar to sexual elitism.  
 

Newsgroups: sci.physics
From: scip1061@nuscc.nus.sg (Marc Paul Jozef)
Subject: Re: BAEZIAN physics and astronomy [was: Space-time IS a semi-Riemannian manifold (?)
Organization: National University of Singapore
Date: Wed, 7 Oct 1992 07:02:39 GMT

I would like to know how I can change the name the university
of Singapore has designated me. It brands me as a hard-core
christian. Moreover, I have no `Dr' or `Prof' preceding my
name, so the whole world knows I'm not doing my home-work.

marc van loo.
From: sawyer@utahep.uta.edu (Lee Sawyer)
Subject: Re: 1992 Nobel Prizes: a prediction
News-Software: VAX/VMS VNEWS 1.41    
Organization: University of Texas at Arlington High Energy Physics Group
Distribution: na
Date: Thu, 15 Oct 1992 15:15:00 GMT

In article <1992Oct15.022403.1496@noose.ecn.purdue.edu>, tekman@ecn.purdue.edu (Erkan Tekman) writes...
>In article <93071@netnews.upenn.edu>, weemba@sagi.wistar.upenn.edu (Matthew P Wiener) writes:
>|> In article <9OCT199221030655@utahep.uta.edu>, sawyer@utahep (Lee Sawyer) writes:
>|> >other is not de Broglie (the work that he was cited for was
>|> >in his dissertation - a unique occurance as well, I believe).
>|> 
>|> Didn't Glaser invent the bubble chamber as a grad student?
> 
>and Mossbauer was a grad student when he came out with the spectrescopy named
>after him.
> 
>E. Tekman 

  ...yeah, and Alison Chaiken pointed out that Josephson won for work done
as a grad student. So I was basically way off base on this one. But look,
in how many of these cases did the committe cite the work actually in the 
dissertation ? I don't know - I hereby resign from making any blanket
statements about the prizes.

  To go back to the first question - how many of the physics prizes
have been awarded to non-PhD's ?

       ================                           
         Lee Sawyer                                  

         Dept of Physics                          
         Univ. of Texas                            
               at Arlington                        

Newsgroups: sci.physics