HDTenEightyP/NetNews huggingface dataset:
From: jbaez@riesz.mit.edu (John C. Baez)
Newsgroups: sci.physics
Subject: Re: Question about electron spin
Date: 28 Sep 92 21:58:40 GMT
Organization: MIT Department of Mathematics, Cambridge, MA

In article <1992Sep27.185539.594@prim> prim!dave@germany.eu.net (Dave Griffiths) writes:
>I've just been reading Roger Penrose's explanation in the Emperor's New Mind
>of the EPR experiment. In this he claims that it is possible to measure the
>spin of an electron in three different directions at 120 degrees to each
>other and obtain the result YES, the spin of the electron is aligned in
>that direction for each measurement. Surely this is incorrect? He has already
>shown that if you measure the spin in one direction and get the answer YES,
>then there is a probability of (1 + cos 120)/2 = 1/4 that a measurement at
>120 degrees to this will also give the answer YES. Fine. But surely, with 
>the wave function having collapsed, it's not possible for three measurements 
>at 120 degrees to each other _all_ to give YES?
>
>If it is possible, has such a result ever been experimentally confirmed?
>
>Please say no.

"Wave function having collapsed," did I hear you say?  I'm not sure
how much that picture is to blame for your puzzlement.  In any event,
Penrose' account as you have described it seems correct.  If you
call the 3 axes A, B, and C, one can measure angular momentum first
along A, then B, then C, and get "yes" each time.  It's worth noting
though that if you then measure angular momentum along axis A again,
you need not get the answer "yes" again.  In fact you will get "yes"
only with a 25% chance.  

Penrose is extremely idiosyncratic in this book, but here he seems
right.

I don't know if the experiment has been done but it seems easy
enough.
From: whitbeck@equinox.unr.edu (Michael Whitbeck)
Newsgroups: sci.physics
Subject: IR fiber optics/waveguides
Summary: waveguides IR
Date: 30 Sep 92 17:17:34 GMT
Organization: University of Nevada, Reno

I would appreciate any information on the availability
and performance of infrared fiber optics or waveguides
(not necessarily fiber).

The spectral ranges of interest are near-IR (700-2500 nm)
and mid-IR (2.5 - 7 microns).

If you have been working in this area or with IR waveguides I
would appreciate receiving e-mail.


I want to measure diffuse reflectance from a (very) rough
surface that is in motion- I can control the movement in the
direction of travel. The distance from the surface to the
instrument will vary and I believe it would be easier to
manipulate a waveguide than to swing the instrument
back-and-forth to maintain the viewing geometry.

Many thanks in advance!

___________________________________________________________
|Mike Whitbeck             | whitbeck@equinox.unr.edu     |
|Desert Research Inst.     | whitbeck@wrc.unr.edu         |
|POB 60220                 |                              |
|RENO, NV 89506            | 702-673-7348                 |
|__________________________|______________________________|

All academics have the potential for being insatiable...
but the chemists are the most expensive and insatiable among the
expensive and insatiable. - J. Martin in "To Rise Above Principle"

Newsgroups: sci.physics
From: f85-tno@nada.kth.se (Tommy Nordgren)
Subject: Re: Cheap laser possible?
Organization: Royal Institute of Technology, Stockholm, Sweden
Date: Wed, 30 Sep 1992 20:32:43 GMT

	In article <1992Sep28.155014.27323@relay.nswc.navy.mil>, bwallet@apssgi.nswc.navy.mil (Brad Wallet) writes:
|> In article <1992Sep28.141907.29179@ucsu.Colorado.EDU>, knapp@spot.Colorado.EDU (David Knapp) writes:
|> |> You might try to check out a Scientific American article of several years
|> |> ago (maybe many years ago, now '79??) where a nitrogen laser is described
|> |> for home building in detail. It is certainly the most affordable and
|> |> easiest.
|> 
|> That was in Scientific American issue June, 1974 in the Amature Scientist
|> column.
|> 
|> Brad
	
	Scientific American have published another article on the subject of
cheap  lasers (The Amateur Scientist, April 1990).
	This is a low temperature copper laser, which lases in green and yellow.

	Tommy Nordgren, Royal Institute of Technology.
From: dbc@ecs.soton.ac.uk (Bryan Carpenter)
Newsgroups: sci.physics
Subject: Re: LARSONIAN Physics and Astronomy
Date: 1 Oct 92 10:53:49 GMT

In <29SEP199213190360@csa1.lbl.gov> sichase@csa1.lbl.gov (SCOTT I CHASE) writes:

>In article <1992Sep28.222259.18699@galois.mit.edu>, jbaez@riesz.mit.edu (John C. Baez) writes...
>>...

>Perhaps.  My tendency to be "optimistic" in this sense is well known 
>to all.  I would prefer to say that QED is not *proven* to be consistent,
>though it is known(*) to be so.  Certainly it is widely believed to be so.

Have there been recent developments here?  I'm a bit out of touch
with field theory these days, but it used to be widely suspected
that QED, like phi^4,  is ``consistent'' (whatever that means,
precisely) only in the case where the renormalised coupling
vanishes---ie only as a theory of non-interacting particles.

(The escape clause was this holds as the cutoff goes to infinity,
and one hopes that new physics comes in at some enormous scale,
so there is some large but finite effective cutoff).

>(*) According to the Oracle at Berkeley.

>-Scott

Bryan
Newsgroups: sci.physics
From: danforth@riacs.edu (Douglas G. Danforth)
Subject: Re: Simple observation about Quantum Kitty Cats
Organization: RIACS, NASA Ames Research Center
Date: Wed, 30 Sep 92 18:48:55 GMT

In <1992Sep30.171247.784@newshost.lanl.gov> jlg@cochiti.lanl.gov 
(Jim Giles) writes:


>Since no *action* at a distance is predicted by QM, there is no
>problem.  Only *correlation* at a distance is predicted.  Such
>correlation is quite commonplace in non-QM contexts using hidden 
>variables.  The QM difference is that hidden variables have been
>shown *not* to be involved.

Detector efficiency is still a loophole that needs to be closed
before hidden variables can be ruled out.

Newsgroups: sci.physics
From: bhv@areaplg2.corp.mot.com (Bronis Vidugiris)
Subject: Re: FTL Experiment (really a metacommentary on reposting)
Organization: Motorola, CCR&D, CORP, Schaumburg, IL
Date: Tue, 29 Sep 1992 20:52:35 GMT

In article <1992Sep29.040246.16482@murdoch.acc.Virginia.EDU> crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass) writes:
)In article <717712154.109@mailbox.bison.mb> Bronis.Vidugiris@mailbox.bison.mb.ca (Bronis Vidugiris) writes:
)(actually he wrote it a while back)
)
)   It only took me about 10 articles before I realized that 
)   Mr. mailbox.bison.mb.ca was having some sort of reposting
)   problem (fidonet site perhaps?).  
)
)   Though it seems good for the digestion, I'd really better stop
)   eating teflon.  

The 'real' me is at areaplg2.corp.mot.com.  Unless - could it be - 
a message from another Bronis in a Parallel Quantum Universe?

<de de de de - insert twilight zone music>

Nah.

Newsgroups: sci.physics
From: isupstud@bnr.ca (Wayne Hutton)
Subject: Can you figure this joke out?
Reply-To: isupstud@bnr.ca (Wayne Hutton)
Organization: Bell-Northern Research Ltd.
Date: Mon, 5 Oct 1992 14:46:25 GMT


The integral of 'e' to the 'x' is a function of both 'u' and 'n'.

If no one can get it I'll post the answer later.

ps. all credit goes to my linear algebra prof (first year college)

-todd.
Newsgroups: sci.physics
From: platt@watson.ibm.com (Daniel E. Platt)
Subject: Re: Can you figure this joke out?
Date: Mon, 05 Oct 1992 16:44:36 GMT
Disclaimer: This posting represents the poster's views, not necessarily those of IBM
Organization: IBM T.J. Watson Research Center

In article <1992Oct5.144625.22281@bcrka451.bnr.ca>, isupstud@bnr.ca (Wayne Hutton) writes:
|> 
|> The integral of 'e' to the 'x' is a function of both 'u' and 'n'.

This statement is incomplete...

Should read:

	The integral of 'e' to the 'x' is a function 'F' of both 'u' and 'n'.
|> 
|> If no one can get it I'll post the answer later.
|> 
|> ps. all credit goes to my linear algebra prof (first year college)
|> 
|> -todd.

Dan
Newsgroups: sci.physics
From: abian@iastate.edu (Alexander Abian)
Subject: Response to  PUTTING VENUS IN AN ORBIT ... and   TIME HAS INERTIA
Organization: Iowa State University, Ames IA
Date: Fri, 2 Oct 1992 13:57:06 GMT

   My statements concerning PUTTING VENUS IN AN ORBIT SIMILAR TO THE ORBIT
OF THE EARTH and TIME HAS INERTIA need no further elucidation, justifi-
cation or proof.  They are explicit, self-explanatory and self-evident.
They are true and they are the way of the future.  I do not necessarily
need the approbation of the so-called guardians of "truth" and "reality".
   
   People will alter the orbit of Venus and the orbits of other planets
(Terraforming is not a radical enough solution).  People will alter the
Tilt of the Earth to avert the persistent occurrences of meteorological
catastrophes, disasters and calamities.
 
   People will conclude that TIME HAS INERTIA and that Principles of
Conservation of Energy and Consistency of the Speed of Light must be
rejected.

   People should study my proposals and further develop them.  Their 
implementation is inevitable.
                                                 Alexander ABIAN
Newsgroups: sci.physics
From: hees@cubic.com (Phil Hees)
Subject: Re: Questions of transparency
Organization: Cubic Toll Systems
Date: Mon, 05 Oct 92 14:40:47 GMT

In article <5761@tuegate.tue.nl> johan@blade.stack.urc.tue.nl (Johan Wevers)
writes:
>davids@spira.bri.hp.com (david sixsmith (contractor)) writes:
>>after all questions of lenses etc were well
>>understood by Newton - did noone have any idea why glass was transparent.
>
>He did have some difficulties with collor correction: Newton tought that it
>was impossible to give the focus point of 2 collors the same position.

This was actually the case given the limited types of glass which were
available to Newton.  The two-element achromat requires glasses with
different dispersion characteristics.

Newton, who first investigated dispersion (the dependence of the angle of
refraction on the wavelength of the incident light), did consider using
more that one lens to perform color correction.  Based on what might have
been too hasty a study of the dispersion characteristics of various
available glasses, he concluded that such correction was impossible.

The result was that Newton turned to reflector telescope design (which
doesn't suffer from chromatic abberations) and invented the modern
telescope.  Given the magnitude of Newton's accomplishments in optics
alone, I think he might be excused for not inventing borosilicates, too.

--
Phil Hees
hees@cubic.com
Newsgroups: sci.physics
From: ramsay@unixg.ubc.ca (Keith Ramsay)
Subject: Re: Spin
Organization: University of British Columbia, Vancouver, B.C., Canada
Date: Mon, 5 Oct 1992 01:37:34 GMT

In article <BvM2xp.En2@well.sf.ca.us> 
metares@well.sf.ca.us (Tom Van Flandern) writes:
...
>     The empirical part of this fact means that no gravitational
>aberration has ever been detected, even though certain observations have
>ten orders of magnitude more sensitivity than needed to detect any such
>aberration which would exist if gravity propagated between masses in the
>manner and at the speed of light.

How was it determined what kind of "aberration" would exist if
gravitation propagated at the speed of light? In particular, are you
claiming anything which is known to be inconsistent with (a) the
orbits are consistent with general relativity, and (b) gravity
propagates at speed c in GR? If not, then please word the claim
differently in the future.

Keith Ramsay
ramsay@unixg.ubc.ca
From: jac@ds8.scri.fsu.edu (Jim Carr)
Newsgroups: sci.physics
Subject: Re: Question about electron spin
Date: 28 Sep 92 13:36:47 GMT
Reply-To: jac@ds8.scri.fsu.edu (Jim Carr)
Organization: SCRI, Florida State University

In article <1992Sep28.174343.714@prim> prim!dave@germany.eu.net (Dave Griffiths) writes:
>
>No wonder they call it spin. :-) Seems the notion of spin in a particular
>direction is a bit meaningless if you can detect it in all three

No, it has a well-defined meaning.  However, when the spin is in a 
particular direction, you can still measure the *projection* of the spin 
on an axis at some angle to that direction.  If the angle is zero, you 
get YES 100% of the time -- which is what gives the "direction" a well-
defined meaning.  If the angle is 90 degrees, you get NO 100% of the 
time -- ditto for well-defined meaning.  It is, say, 45 degrees, then 
you get YES 1/2 of the time since there is a 50-50 projection onto 
these YES and NO axes.  (You cannot get half the spin, since the 
spin is quantized, so instead you get half the particles.) 

>directions. Your comment about polarizing sheets has almost persuaded me,
>however we're dealing there with _aggregates_. I was wondering whether it
>was possible to measure the spin of one single electron three times
>consecutively and get "spin up" in three directions. If you did such a
>measurement at 0, 120 and 240 degrees and got YES each time, and then
>measured it at 180 degrees, would there be a chance (1 + cos 60)/2 (ie the
>angle between the last measurement at 240 and 180) of now getting a YES,
>or does the past history of a measurement at 0 preclude this? Could you

Past history has nothing to do with it, only the last direction of 
polarization matters.  It does not matter how you got there.  The 
reason, of course, is that each measurement "collapses" the wavefunction 
(or, if you prefer, prepares the wavefunction in a new intial state with 
some new set of amplitudes) and you start anew. 

>possibly get a YES at 60 degrees, exactly opposite your YES at 240 degrees?

That would depend whether you were measuring spin "up" or just the 
direction (as with polaroids).  No for the former, of course, and 
yes for the latter. 

>>Is your brain numb yet? 
>
>Yes.

Then you are off to a good start.  I recommend that you think about 
the problem with polaroids, and do a few experiments with them.  It 
is a very good way to learn about the ideas of state vectors.  (I 
am trying to recall if any text uses this approach, my QM lecturer 
did this but not sure if it has its basis in a book you might read.) 

--
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: bweiner@ruhets.rutgers.edu (Benjamin Weiner)
Newsgroups: sci.physics
Subject: Re: Interested in "magical" tones!
Date: 28 Sep 92 23:19:04 GMT
Organization: Rutgers Univ., New Brunswick, N.J.

> [according to LaRouche:]
>All TRUE classical music was performed, according to this article, on a
>slightly different scale-- I forget exactly where, but something like
>A-435, i.e., indistinguishable from A-440 to the vast majority of humans
>(except when played at or nearly at the same time, of course)

Actually during the Baroque era the standard was about A=415 Hz.  This
is a fairly large difference (half a semitone?)  Some early music
people tune to this, I guess.  I seem to recall that the old SCRIBE
reference card used a program for the "415 Players," an early music 
ensemble, as its sample text.  (Am I dating myself?  SCRIBE was a
text-processor that made nice output for your printer, which predated
TeX and has now been utterly supplanted by it.)

Anyway, the difference between A=415 and A=440 _is_ probably large
enough to bring about world fascism and the decline of all cultural
standards.  That LaRouche, he's pretty sharp.
Newsgroups: sci.physics
From: b5249-23@mathcs.sjsu.edu (Kurt Stocklmeir)
Newsgroups: sci.physics
Subject: Spin
Date: 30 Sep 92 21:51:09 GMT
Organization: San Jose State University - Math/CS Dept.


    Tom is an expert in gravity and knows more about gravity than
almost anybody in the world.  Say something Tom, even if your
statements disagree with me.
From: whit@milton.u.washington.edu (John Whitmore)
Newsgroups: sci.physics
Subject: Re: Questions of transparency
Date: 1 Oct 92 01:04:45 GMT
Organization: University of Washington, Seattle

In article <1992Sep25.073432.29995@hplb.hpl.hp.com> davids@spira.bri.hp.com (david sixsmith (contractor)) writes:
>1. What is (are) the inherent qualitie(s) of a substance, such as glass,
>perspex, diamond, & water, which make it transparent ?

	Well, at the microscopic level it is the fact that the scattering
in the material is both elastic and coherent.  In a metal, some
induced electron flow can cause the scattering to be inelastic,
and such phenomena as fluorescence are always incoherent.
At the larger-scale level, it is also important that the
medium not have irregularities (frosted glass isn't as transparent as
clear glass, by most tests).

>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 ?

	Entrainment of charge.  Free (or nearly free) charges are
moving inside the medium in response to the electric excitation,
so that the energy in the wave is not entirely field energy,
but includes kinetic energy and binding energy of the charges,
so that the wave equation is significantly altered.
	One could (equivalently) note that excitations of the
charge give rise to a phase-shifted response wave, and the sum
of the incident wave and the response is a slower-moving
composite wave.

	John Whitmore
Newsgroups: sci.physics
From: dwr2560@zeus.tamu.edu (RING, DAVID WAYNE)
Subject: Re: Expansion
News-Software: VAX/VMS VNEWS 1.41    
Organization: Texas A&M University, Academic Computing Services
Date: Thu, 1 Oct 1992 01:04:00 GMT

baez@ucrmath.ucr.edu (john baez) writes...
>>                                           The region of space which is
>>inside a galaxy satisfies the same local einstein equation as the above
>>recollapsing example, so why do galaxies live so long?
> 
>'Cause they're smaller.  I'm sure one can work out the math, but
>it's bound to amount to just that.  For example, one can have
>a fist-sized ball of iron, which will essentially never collapse
>(quantum fluctuations aside), but a galaxy-sized ball of iron
>would collapse mighty fast.

I'm surprised at you John, you forgot the atomic repusion! :)

I get that a fist-sized ball of superdust weighing in around a kilogram
collapses in about an hour. I think that will be about the same for an
observer in the center of your iron galaxy. But I'm depending on my
already disproven intuition. :)

I also think the size has an effect, along with the empty 'outside'. I.e.
there will be tidal forces which will disturb my intuition. There are no
tidal forces in the closed cosmology. I would then demand that the scale
at which I approximate the star density as a fluid is small enough that
the tidal forces are small. But a given region gets stretched out so
that they become large nevertheless. I haven't decided yet whether this solves
my problem.

Dave Ring
dwr2560@zeus.tamu.edu
From: mapsj@gdr.bath.ac.uk (Simon Juden)
Newsgroups: sci.physics
Subject: Re: Possible?: 2 integers specifying a point in 3D space.
Date: 28 Sep 92 17:12:58 GMT
Organization: School of Mathematics, University of Bath, UK

In the referenced article, gauthier@ug.cs.dal.ca (Paul Gauthier) writes:
>
>Is it possible to specify uniquely, an arbitrary point in 3D space using 
>only 2 integers? IE: You point to any point in space (using a conventional
>three-tuple (x, y, z)). Is it possible for me to respond with 2 integers
>which corrispond to that point and no other? You can even use real numbers
>in your three-tuple, but my response has to be two integers. Also, the
>3D space is infinite in all directions, so the values of each component
>of your three-tuple are completely unconstrained. Is it possible for me
>to use some co-ordinate system and label the point you give me uniquely
>with 2 integers?
>

No - in fact more is true: given any large finite number N you can't even
specify a point on the real line using N integers in the way you suggest. The
reason is that the real line (and 3-dimensional Euclidean space) is bigger than
the integers: in the jargon we say that the integers are "countable" but the
reals are "uncountable". So there can never be what you hope for: what
mathematicians call a "bijection" between \Z^{2} and \R^{3}.

However if you are allowed to discretise your space ie model \R^{3} with a
countable lattice which may (without loss of generality) be viewed as \Z^{3}
then you can specify any point on this lattice using just one integer. There
are lots of ways to do this: one simple (certainly not the best) way would be
to map the three integers (x,y,z) [bijectively] to the positive integer

	2^{|x|}*3^{|y|}*5^{|z|}*7^{1+sgn(x)}*11^{1+sgn(y)}*13^{1+sgn(z)}

(where sgn(x)= +1 if x>0, 0 if x=0 and -1 if x<0)

You could even use this approach if you are allowed to model \R^{3} by \Q^{3},
which is a dense subset, since the rationals are countable (ie there are as
many rationals as natural numbers but more reals). But none of this is very
helpful for considering functions which might arise physically (I assume - if
I'm wrong I'd be most interested to see a counterexample to my assertion!). If
you want to do any mathematics involving "continuous" or "differentiable"
functions then this is not going to provide a way to do it. In short three
dimensions means just that - you can't cut it down to two!

Simon
Newsgroups: sci.physics
From: jbaez@riesz.mit.edu (John C. Baez)
Subject: Re: LARSONIAN Physics and Astronomy
Organization: MIT Department of Mathematics, Cambridge, MA
Date: Mon, 28 Sep 92 22:22:59 GMT

In article <28SEP199211153430@csa1.lbl.gov> sichase@csa1.lbl.gov (SCOTT I CHASE) writes:
>
>>               A SELF-CONSISTENT Theory is MUCH MORE than the ORTHODOX 
>>          physicists and astronomers have!  They CLAIM to be looking 
>
>If by self-consistent, you mean that the theory make one and only one
>well-defined prediction for any observable, which then turns out to 
>match the experimental evidence, then modern physics is certainly 
>self-consistent.

I think you are being rather optimistic here.  For example, QED, or the
standard model, is not known to be consistent.  Nor are they known to be
inconsistent.

>>               Naming the "Super Collider" after Ronald Reagon, as 
>>          proposed, is TOTALLY ABSURD!  If it is built, it should be 
>>          named after a leading particle PHYSICIST. 
>
>A statement I can agree with!!! There is little doubt that the SSC should
>have been the Richard Feynman Center for Particle Physics.  

Wait and see if it works before saying this.  (Naturally, my advisor,
Irving Segal, who disbelieves in a linear redshift-distance relation,
thought that the Hubble telescope was aptly named.)  

Of course I agree with the rest your post about Larson's system, being
a card-carrying orthodox physicist, hard at work at suppressing (or was
it ignoring?) his contributions to physics.
From: firth@sei.cmu.edu (Robert Firth)
Newsgroups: sci.physics
Subject: Re: Defining local, causal etc., was: Hidden variable theories
Keywords: collapse
Date: 6 Oct 92 18:08:22 GMT
Article-I.D.: sei.1992Oct6.180822.3884
Organization: Software Engineering Institute

In article <5804@osc.COM> Joe Keane <jgk@osc.com> writes:

>I agree it's preposterous to say that a measurement here `instantaneously' has
>an effect billions of light years away.

And guess what, I agree with you.  Where I part company with you and Paul
is at the next milestone.  You seem to think that from the premise "P is
preposterous" it is permissible to derive the conclusion "P is false".
I don't; and the history of QM gives me some confidence in that opinion.