HDTenEightyP/NetNews huggingface dataset:
Organization: European Space Agency - Paris
Date: Monday, 9 Nov 1992 14:28:23 EST
From: Sanchez de la Rosa, L. <LSANCHEZ@ESA.BITNET>
Newsgroups: sci.physics
Subject: Re: Do Balloons fly?
 <1dbs8vINNau0@agate.berkeley.edu> <1992Nov6.031615.7269@galois.mit.edu>

It's for me quite amazing all these discussions about matter facts that were
discovered so long ago (more than 2000 years) by our dear Arquimedes.

Regards.
Newsgroups: sci.physics
From: sarfatti@well.sf.ca.us (Jack Sarfatti)
Subject: Picture of gedankenexperiment FTL
Organization: Whole Earth 'Lectronic Link
Date: Fri, 13 Nov 1992 20:14:26 GMT


Someone requested a picture: FYI
Sarfatti quantum connection communication gedankenexperiment



receiver                                   transmitter

p(e')  ------       pair source              ------  e+    _ e^iphi e+
-------|    |   b      ---   a               |    |-------|_|-------\
p(o')  |    |  <--     | |  -->              |    | o- _    o+      |
-------|    |          ---                   |    |---|_|----------__|
       ------                                ------ 1/2 wave
                                                                single
c                                                               counter
       calcite  (angle theta between them)   calcite


p(e') = [1 + sin(2theta)cos(phi - arg<a,e,+|a,o,+>)]/2

p(o') = [1 - sin(2theta)cos(phi - arg<a,e,+|a,o,+>)]/2

p(transmitter counter) = 1

p(e') + p(o') = 1

so local probabilities add to 1 on each side.

The o- 1/2 wave plate and e-phase plate changes entangled pair state

!a,b> = {|a,e,+>|b,e,+> + |a,o,->|b,o.->}/sqrt2

to

|a,b>' = {e^iphi|a,e,+>|b,e,+> + |a,o,+>|b,o.->}/sqrt2

but  |a,o,+> = |a,e,+>e^iarg<a,e,+|a,o,+>

|<a,e,+|a,o,+>| = 1

because the 1/2 wave plate makes |a,e,+> and |a,o,+> have the same
polarization so they are not orthogonal or linearly dependent.

Therefore |a,b>' is disentangled or split into two separate 1-photon states

|a,b>' = |a,e,+> |b>

|b> = {e^iphi|b,e,+> + [e^iarg<a,e,+|a,o,+>]|b,o.->}/sqrt2

p(e') = |<e'|b>|^2

p(o') = |<o'|b>|^2

One can argue that local unitarity for arbitrary 1-photon superpositions
implies

phi - arg<a,e,+|a,o,+> = pi/2

so that the quantum connection signal

p(e') - p(o') = sin(2theta)cos(phi - arg<a,e,+|a,o,+>) = 0

But it is not clear that this argument works for the pair state since

'<a,b|a,b>' = 1

without that condition.

Let experiment decide!






Newsgroups: sci.physics
From: alison@wsrcc.com (Alison Chaiken)
Subject: ferromagnetism: the QM basis
Organization: W S Rupprecht Computer Consulting, Fremont CA
Date: Thu, 12 Nov 1992 05:58:37 GMT

columbus@strident.think.com (Michael Weiss) writes:
>>Alison Chaiken writes:
>>(This is really an indirect
>>manifestation of the Coulomb repulsion between like charges.)
>I don't understand the parenthetical remark.  The exclusion
>principle applies even to uncharged fermions, no?

I guess you were looking for a more detailed answer ;-).  The simplest
details that I know come from the Hartree-Fock theory, which is the
zeroth-order many-body theory of electrons in solids (or atoms).
Here's how one derives the Hartree-Fock equations for the electron
energies: First, form a wavefunction called a Slater determinant which
guarantees that the Exclusion Principle will be satisfied (by taking
linear combinations of single-particle states which change sign when
particles are exchanged).  Next, take the <psi/H/psi> product to
evaluate the energies, where H, the Hamiltonian, involves kinetic and
Coulomb potential energies.  Because of the form of the Slater
determinant, there are TWO types of terms with coefficient e^^2, where
e is the electronic charge.  One is the simple repulsion of an
individual electron to all the others.  The other term is called the
exchange energy because it involves an integral over products like
(a_up b_down -- b_up a_down), where a and b are single-particle
wavefunctions and up, down refer to spin direction.  This exchange
energy is the fundamental origin of the itinerant electron
ferromagnetism of transition metals like Fe, Ni, Co.  It is not a
concocted toy model like the Ising model; it comes from fundamental
QM.

>I wrote:
>    The converse of the preceding statement is that if you have a low-density
>    electron gas, there is an effective net force aligning the spins.

>>Is there a rough-and-ready intuitive explanation for this effect?  Naively,
>>it would seem that the exclusion principle would tend to *anti-align*
>>spins.

That IS the rough-and-ready explanation; the other explanation I know
requires equations.  Exclusion does anti-align spins if they can be
put in the same energy level.  However, you get Hund's rules (of
atomic energy level filling) wrong if you ignore exchange energy; it's
an experimental fact.  I think that exchange energy is one of those QM
concepts that is not particularly intuitive; I view it as an
expression of the delocalization of electrons.

>Obviously this line of thought is too naive.  Is there a qualitative
>explanation that shows how Pauli exclusion --> aligned spins?

Sorry if you think this is too naive, but further discussion may be
beyond the scope of this newsgroup.  I would suggest that you look at
a QM textbook like _Intermediate QM_ by Bethe and Jackiw under
"Hartree-Fock" for more details about exchange energy.  If you want a
really detailed reference specifically about FM in Fe, I can dredge
one up.  Neville Mott's papers about FM are the best.
-- 
Alison Chaiken 				alison@wsrcc.com
(510) 422-7129 [daytime] 		or chaiken@cmsgee.llnl.gov
Look if you like, but you will have to leap.
From: bhoughto@sedona.intel.com (Blair P. Houghton)
Newsgroups: sci.physics
Subject: Re: Religion & Physics Don't Mix
Date: 10 Nov 92 00:39:55 GMT
Organization: Intel Corp., Chandler, Arizona
NNTP-Posting-Host: alfalfa.intel.com

In article <1992Nov9.100028.24613@murdoch.acc.Virginia.EDU> crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass) writes:
>     Are you suggesting that
>     if repeatedly stabbing himself in the abdomen provides some individual
>     a modicum of mental health and a productive life, we should all do
>     it?

Damn you right to hell for implying that mental health
is tantamount to self-mutilation.

				--Blair
				  "You're a fucking psycho, Corky."
From: b5249-23@mathcs.sjsu.edu (Kurt Stocklmeir)
Newsgroups: sci.physics
Subject: Physics Questions
Date: 6 Nov 92 21:54:53 GMT
Organization: San Jose State University - Math/CS Dept.

To the innocent person who asked about the differences between
gravity having an infinite velocity and a velocity = c.

In addition to the rude insulting people and the fighting that goes
on that nobody could find even in the first grade of the worse elementary
school in the world, sci.physics is known not to have the best physics.
Would anybody fly on an airplane made by sci.physics?

If the sun disappeared, and if gravity had an almost infinite velocity,
the gravitational field would disappear with the sun.  If gravity moves
at c, it would take 8 minutes.

There are also differences between the shape and energy of the gravitational
field around things depending on if gravity travels at an almost infinite
velocity or c.  For example there is a difference between the gravitational
field of an electron antielectron and a photon.  Since a photon travels
at c, and since it emits gravity in all directions, if gravity moves at
c, the gravity emitted in front of the photon would be kind of moving with
photon.  Nobody in front of the photon would see the gravity until they saw
the photon.  Then they would get hit with the photon and the gravity at 1
time.  If the photon did not change directions and if the photon did not
interact with anything over a period of time, there would be a large amount
of momentum.  The gravitons would also emit gravitons, some in the forward
direction.  If gravitons travel faster than c, there would be a gravitational
field in front of the photon.  What would be the speed of gravitons are if
they are suppose to travel at c, but they are emitted in the opposite
direction of the photon?

The same thing applies to neutrino scattering.  The neutrino is suppose to
be moving a little slower than c, at c, or in my opinion a little faster than
c.  It emits ws and zs.  About 1/2 of the time, in the forward direction, the
ws and zs are moving faster than c.  Do they only scatter backward?  People
say that ws and zs are virtual particles, but you would fly on a virtual
airplane, even a virtual airplane made by sci.physics?
Newsgroups: sci.physics
From: crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass)
Subject: Re: GR with no Einstein? (Was: Re: No big crunch?)
Organization: University of Virginia
Date: Tue, 10 Nov 1992 19:10:25 GMT

In article <1992Nov10.174154.1255@sun0.urz.uni-heidelberg.de> gsmith@lauren.iwr.uni-heidelberg.de (Gene W. Smith) writes:
>In article <1992Nov9.182446.13635@murdoch.acc.Virginia.EDU> crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass) writes:
>
>>     Though many people were working on gravitation, and always had been
>>     working on gravitation (and there are still people working on 
>>     alternatives), it wasn't like there was any vastly compelling reason to 
>>     overthrow Newton.
>
>Once you've bought special relativity (and about that you have no
>choice) you've *got* to work on alternatives to Newton.  Moreover, you
>are forced into nonlinear alternatives.  I think by working up from
>the linearization, you would be led to a local theory which was
>Einstein's locally, and from there it would become obvious.
>
>Basically, what I am saying is that Einstein's theory in its pure (no
>cosmological constant) form is the simplest classical theory uniting
>gravitation with special relativity, and so would have been discovered
>eventually--in the 40's or 50's, say.

     I buy your premise completely, which is the reason that I 
     think that we would not 'have' it.  By the 50's, say, there
     would have been enough objections to such a classical theory
     that it would not have been accepted (to say nothing of the
     fact that without Einstein psychologically fighting QM at
     every turn, encouraging Schroedinger, etc. 'classical' theories
     may not even have been investigated at all).

     As an example, there are now several fairly classical
     routes out of the 'black body problem'.  Do you 'accept' them?

                             dale bass
-- 
C. R. Bass                                          crb7q@virginia.edu        
Department of Mechanical, 
     Aerospace and Nuclear Engineering
University of Virginia                              (804) 924-7926
From: cegtitd@prism.gatech.EDU (Tim Dodd)
Newsgroups: sci.physics
Subject: Re: Religion & Physics Don't Mix
Date: 10 Nov 92 21:20:00 GMT
Organization: Georgia Institute of Technology

This entire discussion about whether religion & physics mix has provided
abundant evidence that they do not mix.  Those who have been advocating
the converse view illustrate by their very arguments that such a mix
is impossible.

It is true that there are many scientists who are religious.  It is also
true that there are many religious people who are scientifically minded or
at least take an interest in science.  However, there are two very different
modes of thought in operation here.

When a person is thinking scientifically that is what I will call "rational
mode".  In this mode of thought, the sole object is to acquire the truth.
What do we mean by "truth"?  An assertion is judged "true" if it accurately
reflects the nature of reality.  How do we decide if a statement is true?
We devise an empirical test and let reality tell us if the statement is
accurate.

Religious thought is typified by "mystical mode".  In this mode of thought,
it is recognized that there exists a level of "truth" or "reality" to which
mere rational thought does not have access.  Mystical thought acquires
"truth" through revelations of various sorts.  The fundamental "truths" of
religion are not subject to empirical verification because they are defined
in a manner which precludes even the possibility of such testing.

It is not possible to mix these two modes of thought.  Mysticism does not
intrude into science because if it did so, what remained would not be science.
(This doesn't stop some people from trying, though!)  Imagine a paper on
the first detection of the top quark.  The paper describes in great detail the
experimental set-up, the procedures followed, presents the results of
all measurements, etc.  The conclusion of the paper says something like:
"The alert reader will have noticed that nowhere during the course of the
experiment did we see any evidence for the top quark.  However, we know
that they were there because God told us so."  How come we never see a paper
like this in _Physical Review Letters_?

On the other hand, honest theologians admit that God cannot be found through
the use of reason.  A "leap of faith" is required to believe in God.  The
act of taking this leap is mystical by definition, and cannot be rationally
justified.

These two modes of thought are mutually exclusive.  Neither can encompass
the other:  they cannot be mixed.  You can think mystically or rationally,
but you cannot do both at the same time.  People who call themselves
"religious" and "scientific" are not being completely honest.  You can
be religious *or* scientific; you cannot be both simultaneously.

Tim
-- 
Tim Dodd, Research Scientist, Georgia Tech:  cegtitd@prism.gatech.edu
Newsgroups: sci.physics
From: lucas@watson.ibm.com (Bruce Lucas)
Subject: Re: space
Date: Tue, 10 Nov 1992 22:12:30 GMT
Disclaimer: This posting represents the poster's views, not necessarily those of IBM
Organization: IBM T.J Watson Research Center

> How many mutually perpendicular rulers can you affix to a single pivot?
> After you have attached three of them, you won't have room for a fourth.

This seems to amount to saying "it is easy to construct three mutually
perpendicular axes, but no one knows how to add a fourth".  This might
be taken to be pretty good evidence that there are only three
dimensions, and for some things this is about as much proof as you
get, but for something this fundamental it would be interesting to
find a proof more solid than "we don't know how to add a fourth
mutually perpendicular ruler".

>                     How do I know that time is one-dimensional?
> I'm not sure.  It certainly is a good working hypothesis until someone

This amounts to saying "we've constructed a theory that makes good
predictions on the basis of four-dimensional spacetime".  Again, good
evidence but not a proof.

Just to make this seem more plausible: consider a form of life that
might evolve on the surface of a very smooth planet with very high
gravity.  Suppose these beings were very flat, and in fact consisted
of a single layer of cells.  Their retinas for example would consist
of a single line of cells.  To them the world might seem
two-dimensional, because sensing or causing anything to happen in the
dimension perpendicular to the surface of the planet would be very
difficult.  They would have to rely on more sophisticated observations
to deduce the existence of a third dimension.

Note that I'm not saying in any way that I believe something like this
is the case, but rather that it would be interesting to see a proof
for something this fundamental.  Indeed, I have been provided by email
with a reference which I will look up:

A simple proof that the world is three-dimensional, by T. Morley,
SIAM Review 27 (1985), pp. 69-71   

Newsgroups: sci.physics
From: ramsay@unixg.ubc.ca (Keith Ramsay)
Newsgroups: sci.physics,talk.religion.misc
Subject: Re: Religion & Physics Don't Mix
Followup-To: talk.religion.misc
Date: 8 Nov 1992 01:40:53 GMT
Organization: University of British Columbia, Vancouver, B.C., Canada
NNTP-Posting-Host: unixg.ubc.ca

In article <1992Nov6.145757.26607@aee.aee.com>, gene@aee.aee.com 
(Gene Kochanowsky) writes:
| 	Faith is the unquestioning acceptance of beliefs. This is important,
| if you question the beliefs, then you do not have faith. Ask any priest,
| minister, mullah, rabbi, shaman, witch doctor you come across. If you wish
| to become a "__________" (fill in the blank), then you must accept fully 
| the "_________" (fill in the blank) of "__________" (fill in the blank). 

Not so- I was for many years a member of a Christian church, and it
was not generally taught that belief should be unquestioning. There
are those who believe that it should be, but in our congregation the
contrary was periodically asserted from the pulpit: you *can* question
your faith. In fact, it was sometimes recommended.

sschaff@roc.SLAC.Stanford.EDU (Stephen F. Schaffner) writes:
|	This is complete nonsense.  There may be religious leaders who 
|demand unquestioning acceptance of belief, but I've certainly never met one.  
|
|As a matter of interest, how many have you actually asked?

I also ask this question of Mr. Kochanowsky: have you, indeed, asked
priests, ministers, mullahs, rabbis, shamans, or witch doctors what
they think? How many? Have you investigated Buddhism, for example?

There have also been many religions where it is *action* that counts
primarily, rather than belief.

In article <1992Nov7.212535.312@aee.aee.com> 
gene@aee.aee.com (Gene Kochanowsky) writes:
>	What planet do you come from? It is not Earth.

You are being unnecessarily rude, and you make your lines too long for
my CRT.

>There can be no religion without faith. With no faith, the
>congregation becomes a social club of like thinking people. If you do
>not accept the common understanding of the word, look it up in the
>dictionary.
>
>	Webster's New Collegiate Dictionary -faith 
>		1. a: allegiance or duty to a person: LOYALTY b:
>			fidelity to one's promises

We can stop here. Religion is typically a matter of *commitment*-- but
not necessarily to *belief*, possible instead a given practice. The
word "faith" is often used, it is true, to mean other things.

Followups set to talk.religion.misc.

                       "In no way, shape or form did Kevin represent
Keith Ramsay            a viable alternative to mental illness."
ramsay@unixg.ubc.ca                  -Phillip K. Dick, _VALIS_
Newsgroups: sci.physics
From: matt@physics3.berkeley.edu (Matt Austern)
Newsgroups: sci.physics
Subject: Re: Some physics questions
Date: 6 Nov 92 13:42:08
Organization: Lawrence Berkeley Laboratory (Theoretical Physics Group)
Distribution: na
	<5NOV199211284285@csa2.lbl.gov> <1992Nov6.175022.13136@galois.mit.edu>
	<6NOV199212364099@csa1.lbl.gov>
Reply-To: matt@physics.berkeley.edu
NNTP-Posting-Host: physics3.berkeley.edu
In-reply-to: sichase@csa1.lbl.gov's message of 6 Nov 1992 12:36 PST

In article <6NOV199212364099@csa1.lbl.gov> sichase@csa1.lbl.gov (SCOTT I CHASE) writes:

> The speed of light is what it is for *some* reason, or it would have a
> different value!  (I know I'll get flamed for this one.)  I expect that
> this reason will ultimately be accessible to us.

I agree that the speed of light is what it is for some reason, but I
don't think that the reason is particularly interesting or
fundamental.

The speed of light is a dimensional quantity, so it has the value that
it does only because we happen to use a certain set of units; I think,
then, that a better way to phrase the question is: why do we choose to
measure distances in centimeters and times in seconds?  

That's not a trivial question, of course; centimeters and seconds (or
meters and minutes, or whatever) are a natural scale for humans.  So
the question is: what is it about atomic physics, chemistry, and
biology, that makes this scale natural for us?  I think we know enough
about these fields so that we do at least have a partial answer to
that question.

There even is, actually, one particle-physics way of phrasing this
question that makes it somewhat more interesting: the "natural" units
for length and time are the Plank length and the Plank time.  So why
is it that the physics that we see around us is on scales so very
different?  This, of course, is just the old hierarchy problem
reappearing again: why is it that the QCD scale and the electroweak
scale are so much smaller than the Plank scale?
--
Matthew Austern                   Just keep yelling until you attract a
(510) 644-2618                    crowd, then a constituency, a movement, a
austern@lbl.bitnet                faction, an army!  If you don't have any
matt@physics.berkeley.edu         solutions, become a part of the problem!
Newsgroups: sci.physics,sci.math
From: asimov@wk223.nas.nasa.gov (Daniel A. Asimov)
Subject: Re: What's a manifold?
Organization: NAS, NASA Ames Research Center, Moffett Field, California
Date: Tue, 10 Nov 92 03:13:24 GMT


In article <1992Nov10.000228.14551@samba.oit.unc.edu> Bruce Scott writes:
>asimov@wk223.nas.nasa.gov (Daniel A. Asimov) writes:
>
>>As has been mentioned, it *is* a theorem that all manifolds do occur
>>as subspaces of some Euclidean space: in fact, any n-manifold embeds in R^(2n).
>>
>>This is a pleasant theorem, but it would be inappropriate to take this as a 
>>definition.
>
>What about the one-dimensional helix embedded in R^3. Is the helix not a
	[...]
>Someone educate me on this.
>
>Dr Bruce Scott
-----------------------------------------------------------------------------------

A manifold is purely a topological or differential-topological notion, without
any specific metric assigned.  Your helix is the same as R^1 as a smooth manifold,
so as such it embeds not only in R^2 but even in R^1.

There is another notion, that of a Riemannian manifold.  This is a smooth manifold
supplied with a way of defining the speed of any curve at any point--as a consequence
you can define lengths of curves and distances between any two points in an appropriate 
way.  However, as a Riemannian manifold, your helix is isometric to R^1 and so embeds
isometrically in R^1 (!)  

Yet a third notion is a manifold which happens to be a metric space which arose through
embedding the manifold in Euclidean space, by measuring the distance across the Euclidean
space.  Interestingly enough, this is not very often considered in math research.  

But as *such*, with the extrinsic metric (the one obtained from the distance across R^3), 
your helix will, of course, *not* embed "isometrically" in R^2, which I believe is your 
point.  That is, this extrinsic metric on a copy of R^1 cannot be reproduced with the
extrinsic metric from some embedding of R^1 into R^2.

It would be interesting to know more about what kind of extrinsic metrics can arise 
from smoothly embedding manifolds in Euclidean space.


Dan Asimov
Mail Stop T045-1
NASA Ames Research Center
Moffett Field, CA 94035-1000

asimov@nas.nasa.gov
(415) 604-4799
Newsgroups: sci.physics