HDTenEightyP/NetNews huggingface dataset:
From: jac@ds8.scri.fsu.edu (Jim Carr)
Newsgroups: sci.physics
Subject: NOVA is about Leo Szilard
Summary: Tuesday "Genius behind the bomb"
Date: 27 Sep 92 18:35:33 GMT
Reply-To: jac@ds8.scri.fsu.edu (Jim Carr)
Distribution: usa
Organization: SCRI, Florida State University

Just a program note, for those of you interested in the History of 
Physics.  The program NOVA on PBS is featuring a story about Leo 
Szilard and his involvement in the development of the bomb.  It 
airs Tuesday (see local listings for the time, usually 8 or 9pm) 
of this week (29 September) and is titled something like "The 
Genius behind the Bomb" if you want to double check with your 
local TV listing. 

Leo Szilard is, of course, the man who pushed Einstein to write the 
letter to Roosevelt warning of the importance of nuclear weapons and 
saw that the letter got through channels so it would actually be 
hand delivered to Roosevelt by someone FDR knew and trusted. 

Szilard is less well known (unless you have seen the Oppenheimer 
biography or read some of the history of the Manhattan Project) 
for his scientific contributions.  Perhaps the most important was 
his effort to get truely pure graphite for cross section tests, so 
that the error in earlier measurements was found out and a graphite 
"pile" was built rather than a heavy-water reactor. 

Later, Szilard led the movement to keep the bomb from being used 
against Japan, and helped found the "Bulletin of Atomic Scientists".
A very interesting man, so it should be an interesting program. 

( I am a bit disappointed tho.  When I first saw the title, I had  )
( hoped it would be about Stan Ulam and Nick Metropolis.  Oh well. )

--
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: exuptr@exu.ericsson.se (Patrick Taylor)
Newsgroups: sci.physics
Subject: Re: Cheap laser possible?
Date: 25 Sep 92 20:29:42 GMT
Organization: Ericsson Network Systems, Inc.
X-Disclaimer: This article was posted by a user at Ericsson in North America.
              The opinions expressed are strictly those of the user and
              not necessarily those of Ericsson.

In article <1992Sep25.122819.29025@alf.uib.no> sigurd@novaja.NoSubdomain.NoDomain (Sigurd Tjelmeland) writes:
>From: sigurd@novaja.NoSubdomain.NoDomain (Sigurd Tjelmeland)
>Subject: Cheap laser possible?
>Date: Fri, 25 Sep 92 12:28:19 GMT

>I have understood that one of the most expensive parts
>of a laser is the mirror that lets just a little light
>through. What would happen if one substituted this
>with a fully reflecting mirror with some small holes
>drilled in it. Of course this would set up some
>interference pattern on the beam, but would a laser
>beam be produced this way?

>Just curious,

>Sigurd 
>e-mail: sigurd@imr.no

If I understand my physics this is what you have with a semi-silvered
mirror anyway.  You can't split the photons in half.
 ----------------------------------------------------------------------------
    "This must be Thursday.  I never could get the hang of Thursdays"
                                                       - Douglas Adams
  - Patrick Taylor                                       (Arthur Dent)
    Ericsson Network Systems
    exuptr@exu.ericsson.se                       "Don't let the .se fool you"
    or exuptr@ZGNews.Lonestar.Org, exu.exuptr@memo.ericsson.se
From: hees@cubic.com (Phil Hees)
Subject: Re: Understand...!!!!
Organization: Cubic Toll Systems
Date: Mon, 05 Oct 92 13:54:06 GMT

matmcinn@nuscc.nus.sg (Mcinnes B T (Dr)) writes:
>I am holding in my hand a baloney sandwich. I hereby declare that this
>is an instance of a clock. Now I note that as the baloney sandwich
>decreases, so does my hunger. Since time is what a clock measures, I
>deduce that: Time is hunger.
>
>In short, this definition of time is a load of baloney. Time is NOT what
>you measure with a clock. Time is the length of timelike worldlines. Its
>definition has nothing to do with the way you happen to measure it, which
>is a mere technological bagatelle.

Interesting.  I think Einstein would have disagreed with you.  In fact, if
memory serves me correctly, he himself once said that "Time is that which
a clock measures."  (Granted, this is an argument by appeal to authority,
but I don't think that such tactics are entirely without merit when the
authority cited is _the_ authority.)


Dr. Mcinnes later adds:
>I am a serious person with a vast store of good will. But you know that
>baloney is not a clock because you know that it doesn't measure time.
>That's because you know that time exists independently of devices used
>to measure it. It's about time [so to speak] to drive a stake [or is
>that steak?] through the heart of operationalism. .

Of course we agree that some clocks are better than others, and we do have
an abstract concept of time which allows us to talk about measurement
errors of even the most precise atomic clock.  Furthermore, without an
abstract concept of time, how would one know how to design a good clock?
One might wind up with a baloney instead.  ;)

But it is very important to acknowledge that time _is_ what clocks
measure, and that length _is_ what meter sticks measure, lest one be
mislead by a faulty abstraction.  Einstein's thought experiments involved
putting real clocks, meter sticks and observers in various situations and
determining what would happen to them.  If he hadn't believed that time is
what a clock measures, he would never have formulated relativity; he would
still be trying to explain why his clocks were misbehaving.

Remember Mach's Principle.

--
Phil Hees
hees@cubic.com
From: train@ccwf.cc.utexas.edu
Newsgroups: sci.physics
Subject: Re: Questions of transparency
Date: 6 Oct 92 21:06:13 GMT
Article-I.D.: ut-emx.81193
Organization: The University of Texas at Austin, Austin TX

In article <1992Sep23.071825.4702@hplb.hpl.hp.com> davids@spira.bri.hp.com (david sixsmith (contractor)) writes:
>
>Could anyone answer for me the following questions
>
>1. What is (are) the inherent qualitie(s) of a substance, such as glass,
>perspex, diamond, & water, which make it transparent ?
>
>2. What is the mechanism which makes the speed of light lower when travelling
>in such a medium as opposed to traveling in a vacuum ?
>
Well, the answer to (2), in a simple, concise word, is density.  Its about the same reason why you can't run as fast in water as you can on land - the water is denser than the air, therefore you move slower through it.  The speed of light is (frequency * wavelength).  This is about 3 X 10^8 m/s in a vacuum and slower in other media.  When light travels from say air to water, its wavelength becomes shorter and thus the speed of the light (wave) is lowered.  The frequency of a wave (or wave packet) cannot ch


ange once it has began moving.  You can change the frequency at the source but that affects the waves that propoget behing the wave in question.  Anyway, when the wave enters a new medium, its wavelength will change based on the characteristics of thenew medium and thus the speed of the wave will change.

I'm sure all of this is explained better and in more detail in a quantum mechanics class, but I haven't got that far yet.  I'm just in waves and optics now.  QM comes next semester.  QM probably explains question 1 but I don't really know.

>Thanks
>
Sure, anytime.  Hope I helped.  If anyone can add to or correct what I said, feel free.  I do get my physics mixed up at times :)


-- 
*******************************************************************************
*  "My neural pathways have become accustomed    |    Alton R. Pouncey II     *
*   to your sensory input patterns."             |  train@ccwf.cc.utexas.edu  *
*******************************************************************************
From: paul@mtnmath.UUCP (Paul Budnik)
Newsgroups: sci.physics
Subject: Re: Simple observation about Quantum Kitty Cats
Date: 2 Oct 92 15:37:16 GMT
Organization: Mountain Math Software, P. O. Box 2124, Saratoga. CA 95070

In article <1992Oct2.015248.25672@unixg.ubc.ca>, ramsay@unixg.ubc.ca (Keith Ramsay) writes:
> In article <298@mtnmath.UUCP> paul@mtnmath.UUCP (Paul Budnik) writes:
> > Interpretations exist for quantum mechanics because the theory is not
> >formalizable. One cannot define a model for a quantum mechanical system
> >in ZFC. ...
> 
> I think this is somewhat misleading. I don't see what ZFC particularly
> has to do with it, nor "formalizability". The ambiguities in the
> interpretation lie mainly in what the terms, as formalized (which can
> be done in a variety of ways), should be taken to mean. It is not so
> much a mathematical or theoretical problem as a philosophical problem.

In QM there is a disconnect between the theory, which talks only about
probabilities, and experimental observations. It is this disconnect
that is the source of the problems of interpretation. One literally
does not know what one is talking about when one starts discussing
inherently random processes, as opposed to statistical models that result
from incomplete knowledge or an incomplete model. Saying that one
cannot formalize this in ZFC is a way of saying, in a precise way, that
one does not know what one is talking about.

> Are you saying that probabilistic theories in physics are inherently
> dubious?

Only those that take probability as an innate aspect of the theory.
There is no problem with probabilistic theories that are based on
incomplete information or an incomplete model.

> It is not clear that there even exists such a notion of "random
> sequence" as you seem to think would be required. (There are, of
> course, definitions of "random sequence", just not of the sort meant
> in this context.) People can perfectly well formalize probability
> theory, however.

I have no problems with probability theory. It is the notion of an
inherently random process that cannot be formalized.

> Probabilistic models, on one interpretation, tell us how thoroughly to
> expect certain events to occur, how much confidence to place in events
> occurring.  It is not clear that one ought somehow to be able to
> convert such a theory into one which gives a black-and-white criterion
> for when a sequence of events does or does not conform to
> expectations- for whether the sequence is "a random sequence" or
> isn't. Confirmation is a matter of degrees.

One can develop an algebra of probabilities and apply this to any model.
This is completely different than formalizing the model itself. The latter
is the problem with quantum mechanics.

> Yet I don't think it has persuaded any of us to abandon probabilistic
> models.

It should give you food for thought if you advocate a physical model
in which probability is an innate property.

Paul Budnik
Newsgroups: sci.physics
From: harper@kauri.vuw.ac.nz (John Harper)
Subject: Re: How do you draw a straight line?
Organization: Victoria University of Wellington
Date: Mon, 5 Oct 1992 01:42:08 GMT

In article <1992Oct2.224220.24242@access.usask.ca> choy@skorpio.usask.ca (I am a terminator.) writes:
>How do you know that the line you draw is really straight? 
Machine tool makers faced this at the beginning of the Industrial Revolution
around 200 years ago. The practical test used was: take 3 bars of iron, work 
on all 3 with a hand file until any two fit together either way round with 
no gaps visible anywhere. Now you can think about making your first lathe...

John Harper Mathematics Dept. Victoria University Wellington New Zealand
From: m1dxm00@fed.frb.gov (Douglas X. McManus)
Newsgroups: sci.physics
Subject: large deviations of sums of correlated variables
Keywords: statistical mechanics, large deviations
Date: 2 Oct 92 20:36:26 GMT
Reply-To: m1dxm00@fed.frb.gov (Douglas X. McManus)
Organization: Federal Reserve Board, Wash, DC

I have a problem that may fall into a standard class of problems delt with in statistical mechanics that utilizes large deviation theory.

My problem is to come up with an analytic (asymptotic) approximation to the following probability:

PR{ Sn < C}

where Sn= (Y1 + ... + Yn)/n

and Yi = min[0, Xi - Mi]

Mi are constants

X = (X1, ..., Xn)' are jointly normally distributed with differing variances but a constant correlation between any two elements of X.  

In short, I am interested in the asymptotic properties of sums of tails of correlated normal variates.

I expect that the solution has the form:

PR{Sn < C} === K exp(-nI) where both K and I are functions of the Mi's and the means and correlations of the X's.  Some times this expression has the more formal representation:

(1/n) log( PR{Sn < C} ) = I(parameters of the problem).

and I is refered to as a rate function.

If the X's were only iid there are results I've found that seem to apply.  The dependence structure appears to make this a much harder problem.

Any suggestions?
From: btbg1194@uxa.cso.uiuc.edu (Bradley T Banko)
Newsgroups: sci.physics
Subject: PC Parallel Port for Expt Control?
Date: 5 Oct 92 22:12:43 GMT
Organization: University of Illinois at Urbana

I want to use the datalines coming out of a PC (compatible) computer
parallel printer port to control an experiment.  I just need on/off lines.

Has anybody done this?  And can somebody tell me (or point me to info on)
how to do it?  (C language "outp()" port calls needed, pinout on the DB25
port connector coming out of the PC, etc.)

Thanks in advance for your comments.

Brad Banko


-- 
Brad Banko;  Dept of Physics;  U of Illinois;  b-banko@uiuc.edu
=========================================================================
Tatiana Gutsu for President!                     73 de kb8cne @ n9lnq.il
Newsgroups: sci.physics
From: jbaez@riesz.mit.edu (John C. Baez)
Subject: Re: Can Information Have Physical Units?
Organization: MIT Department of Mathematics, Cambridge, MA
Date: Tue, 6 Oct 92 17:12:21 GMT

In article <1992Oct6.042539.9893@noose.ecn.purdue.edu> tekman@dynamo.ecn.purdue.edu (Erkan Tekman) writes:

>information is indeed unitless, one has for the hamiltonian
>
>     H = H_o + h I
>
>      [etc.]
>
>i just copied these from J. D. Brasher, Int. J. Theor. Phys. vol 30, 979
>(1991), by the way ;-)

I would take anything read in this journal with a large grain of salt;
it is famous for highly speculative (and often dubious) stuff.  It is
the place where my second cousin published his refutation of special
relativity.  I have never seen a Hamiltonian that contained an
"information" term; it might be interesting to consider, but if you want
to get an idea of how ordinary physicists think this article is probably
the wrong place.
Newsgroups: sci.physics
From: sarfatti@well.sf.ca.us (Jack Sarfatti)
Subject: NONLOCALITY, HIDDEN VARIABLES, ACTION AT A DISTANCE
Organization: Whole Earth 'Lectronic Link
Date: Sun, 4 Oct 1992 02:52:21 GMT


H.D.Zeh in THE DIRECTION OF TIME (Springer-Verlag, 1992) p.90 writes:
"In the formalism of quantum theory, the discussed nonlocality is
kinematical (a property of the state) , and, therefore more appropriately
called non-separability or entanglement. Until 1964 it was conceivable that
it might some day be explained in terms of statistical correlations between
hidden variable. Bell's (1964) analysis, based on gedanken experiments
discussed by Einstein, Podolsky and Rosen (1935) demonstrated however that
such a hypothetical structure behind quantum theory - even if not directly
observable in principle - would itslf have to possess nonlocal properties
in order to reproduce the predictions of quantum theory. Although these
nonlocalities could then have a dynamical origin (be caused by an action at
a distance) this action would have to act superluminally."

Indeed, in my gedankenexperiment (i.e. transmitter interferometer with
encoding phase plate in one path, half-wave plate in other, unitary beam
recombiner with 90 degree phase shift between reflected and transmitted
waves, and second coherent recombination of both inteferograms at a single
final transmitter counter giving variable controllable polarization at far
away receiver) this objectively real quantum action at a distance can be
measured in an unequivocal unambiguous way. This superluminal action is
relativistically invariant trivially since it is pre-metrical in John
Wheeler's "pregeometry" having no dependence on the space-time interval
separating the two detections of the the two photons in the same connected
pair.

Newsgroups: sci.physics
From: firth@sei.cmu.edu (Robert Firth)
Subject: Re: Quantum Zeno Effect, Part 1.
Organization: Software Engineering Institute
Date: Tue, 6 Oct 1992 12:07:07 GMT

In article <1992Oct6.024752.20086@galois.mit.edu> jbaez@riesz.mit.edu (John C. Baez) writes:

>Oh-oh, not this again.  The point, as I have argued earlier, is that no
>physically reasonable process can give EXACTLY exponential decay; very
>general arguments show that there is a short "plateau" before the curve
>approximates an exponential.

Yes, there are several models of the decay process that predict a plateau.
However, last time I checked, all of them predict that the length of time
spent on this plateau is smaller than hbar/delta-E, which means the
plateau is unobservable.  If that's not so, I'd appreciate a correction.
From: davids@spira.bri.hp.com (david sixsmith (contractor))
Date: Wed, 23 Sep 1992 07:18:25 GMT
Subject: Questions of transparency
Organization: Hewlett-Packard Laboratories, Bristol, England
Newsgroups: sci.physics
X-Newsreader: TIN [version 1.1.1 PL6]


Could anyone answer for me the following questions

1. What is (are) the inherent qualitie(s) of a substance, such as glass,
perspex, diamond, & water, which make it transparent ?

2. What is the mechanism which makes the speed of light lower when travelling
in such a medium as opposed to traveling in a vacuum ?

Thanks

--
--------------------------------------------------------------------------------
| Dave Sixsmith                       |  Disclaim, disclaim, disclaim, etc.    |
| Bristol, England                    |                                        |
--------------------------------------------------------------------------------
Newsgroups: sci.physics
From: jbaez@riesz.mit.edu (John C. Baez)
Subject: Re: How do you draw a straight line?
Organization: MIT Department of Mathematics, Cambridge, MA
Date: Tue, 6 Oct 92 04:16:51 GMT

In article <12950087@hpspdla.spd.HP.COM> ric@hpspdla.spd.HP.COM (Ric Peregrino) writes:
>
>How about a taught string?

Depends what you teach it.  You can't teach an old string new tricks.

Oh - a TAUT string!  Yes, that's a simple way to get get a straight line
"by definition".  The machine I had in mind was more complicated....


From: davids@spira.bri.hp.com (david sixsmith (contractor))
Date: Fri, 25 Sep 1992 07:34:32 GMT
Subject: Questions of transparency
Organization: Hewlett-Packard Laboratories, Bristol, England
Newsgroups: sci.physics
X-Newsreader: TIN [version 1.1.1 PL6]

1. What is (are) the inherent qualitie(s) of a substance, such as glass,
perspex, diamond, & water, which make it transparent ?

2. What is the mechanism which makes the speed of light lower when travelling
in such a medium as opposed to traveling in a vacuum ?

I only ask these questions because they seem to me simple questions which
I would expect to know the answer to, but I having asked a number of graduate
scientists, I can't get a sensible answer. I think I know how (2) will be
answered, but I've got a follow up.

This isn't in any way homework. Am I getting no response because no-one knows ?

It seems sci.physics is dominated by arcane quantum mechanists, abstruse
general relativationists with a good mixture of non-scientists thrown in.

-----------------------------------------------------------------------------
| Dave Sixsmith                    |  Disclaim, disclaim, disclaim, etc.    |
| Bristol, England                 |                                        |
-----------------------------------------------------------------------------
Newsgroups: sci.physics
From: abond@rvgs.vak12ed.edu (Andrew H. Bond)
Subject: Re: Time travel
Organization: Virginia's Public Education Network (Roanoke)
Date: Tue, 29 Sep 92 04:36:31 GMT

One of the predictions of Einstein's general theory of
relativity is that gravity causes time to slow down. The
concentrated gravity of a black hole is very great. Time slows
as one approaches the event horizen, and at the event horizen
time stops altogether so far as any observer(outside) is
concerned. If we stood outside a black hole and watched someone
fall in, we would see him frozen outside the event horizen for
all time.
	The perception of time by the person falling would be
somewhat different. He would remain concious inside the event
horizen(ignoring tidal forces which would almost certainly be
lethal) and to him passage of time would seem normal, though it
would appear that the universe, after having advanced far into
the future as he approached the horizen suddenly reversed
itself, getting younger rapidly in microseconds it takes to
reach the singularity at the center. If a person could
re-emerge from the black hole sometime after having passed the
event horizen then our hardy traveller would indeed find
himself in anothertime. The only problem is that such a
re-emergence from a static black hole are mathematically
verboten.
	A real black hole, almost certainly rotating, is
another story. With a rotating black hole the singularity is
not a point, but a ring. The mathematics of raotating black
holes are very complex. It seems as if a spaceship entering a
rotating black hole at an angle to the equitorial plane could
pass THROUGH the singularity. Where and when such a trip would
deposit our hardy traveller is open to conjecture, but
certainly greatly removed in both time and space.	

	-AHB
-- 

		Andrew H. Bond

			no matter how bad the election gets remember:
From: johncobb@ut-emx.cc.utexas.edu (John W. Cobb)
Newsgroups: sci.physics
Subject: Re: Gravity-NEUTRALIZING Invention
Date: 28 Sep 92 19:50:54 GMT
Reply-To: johncobb@ut-emx.cc.utexas.edu (John W. Cobb)
Organization: The University of Texas at Austin

In article <1992Sep21.163859.1311@cnsvax.uwec.edu>,
mcelwre@cnsvax.uwec.edu writes:
|>
|>    
|>
|>                         Gravity-NEUTRALIZING Spacecraft
|>
|>               NASA should build an experimental spacecraft based on 
|>          U.S. Patent #3,626,605 [at least $1.00 per complete copy from 
|>          U.S. Patent Office, correct 7-digit patent number required], 
|>          titled "METHOD AND APPARATUS FOR GENERATING A SECONDARY 
|>          GRAVITATIONAL FORCE FIELD", awarded to inventor Henry W. 
|>          Wallace on Dec. 14, 1971.  ...
|>                                        Robert E. McElwaine
|>                                        B.S., Physics and Astronomy, UW-EC
|>                                     

It Looks like ol' Bob E. been into the fire water in Eau Claire. :>

-jwc                                                                     
Newsgroups: sci.physics