HDTenEightyP/NetNews huggingface dataset:
From: kim@Lise.Unit.NO (Kim Gunnar St|vring \yhus)
Subject: Re: STRUCTURE OF TIME
Organization: Norwegian Institute of Technology
Date: Tue, 29 Sep 92 14:04:50 GMT

In article <1992Sep29.115101.1@tnclus.tele.nokia.fi>, hporopudas@tnclus.tele.nokia.fi writes:
 > 
 > In article <1992Sep28.124538.28823@ugle.unit.no>, kim@Lise.Unit.NO
 > (Kim Gunnar St|vring \yhus) writes:
 > > In article <1992Sep28.091054.1@tnclus.tele.nokia.fi>,
 > hporopudas@tnclus.tele.nokia.fi writes:
 > >  >
 > >  > In article <1992Sep24.102014.1@tnclus.tele.nokia.fi>,
 > >  > hporopudas@tnclus.tele.nokia.fi writes:
 > >
 > >  >      "I think that atheistic scientists are fully reponsible for...
 > >  >    ...all kind of evil will be in full power in all around the world."
 > >
 > > So the scientists are responsible for the...
 > > ...the suffering of learning how the universe work, and so on.
 > >
 > 
 >   You don't seem to realize forest from trees. I meant ordinary peoples
 >   mental suffering, which is caused by these undeveloped peoples.

Those people I described look quite ordinary to me. By undeveloped peoples
I suppose you mean your 'atheistic scientists'. And I have observed and
experienced MUCH more suffering from religion than science. I have also
observed and experience much more pleasure and happiness from science than
from religion.

 > > And as for the 'good' doctrine of God: Have...
 > > ...and learning children lies, for example, all in the name of God.
 > >
 > 
 >   What truth, history of undeveloped peoples. ?

Any truth. One like that too.

 > > No, it's not us atheistic scientists who are evil. We just try to find truth.
 > > ...
 > > Post Scriptum: I know I'm gonna get flamed for this, but it felt nice to be
 > >                totally honest for once.
 > 
 > 
 >   "Mads so. peoples without self-disipline, become entangled only in
 >    pleasant's trap when they only choose pleasant instead of good, and they
 >    get lost so. they do not ever reach the goal to become happy."

This is not what was discussed. Keep to the subject!
Or do you confuse science and atheism with pleasure-seeking and undiscipline?
If that's the case, you are mistaken. Learn what the words mean before using
them.

Kim0
Newsgroups: sci.physics,sci.math
From: craig@jido.b11.ingr.com (Craig Presson)
Subject: Re: How do you draw a straight line?
Reply-To: craig@jido.b11.ingr.com
Organization: Intergraph Corporation, Huntsville, Alabama
	<1992Oct6.030213.20215@galois.mit.edu> <stephen.718357265@mont>
Date: Tue, 6 Oct 1992 14:27:03 GMT

In article <stephen.718357265@mont> stephen@mont.cs.missouri.edu (Stephen Montgomery-Smith) writes:
[...]
   How about pulling a piece of string taut?  Won't that give a straight line?

   Stephen

Hmmmmmmm ...

"No power on Earth, however great,
Can stretch a string, however fine,
Into a horizontal line
That shall be absolutely straight."

-- Author unremembered, it's in _Fantasia Mathematica_.

Levity aside, either method can make a line straight enough for
purposes of illustration. After all, how about all that irregularity
in the paper, and your desk? That corrupts your drawings too! And
those damned imperfect pencil points! Although I suppose, being a
model of the apex of a cone, they satisfy the philosophical objection
better than some piece of brass or plastic from K-Mart does for a line.
:-)

-- Craig
From: carlip@landau.ucdavis.edu (Steve Carlip)
Newsgroups: sci.physics
Subject: Re: How old is the universe?
Date: 29 Sep 92 17:53:16 GMT
Organization: Physics, UC Davis

In article <1a3j6vINNsh9@agate.berkeley.edu> ted@physics.Berkeley.EDU (Emory F. Bunn) writes:
>[...]
>I believe, based on my
>admittedly limited understanding of measure theory, that the space
>of 3-geometries is simply "too big" to admit a well-behaved measure
>that would allow one to talk about probabilites.  (I have formed
>some vague arguments in my mind in support of this position,
>but they're far from being rigorous enough to convince anyone else.)
>
>I hope that I am wrong about this, as I think it would be very nice 
>to have such a measure.  Is there anyone out there who can be more 
>definitive about this than I can?
>
Well, there are certainly plenty of "physicists' measures" on the
space of three-geometries.  This space admits a natural metric, the
DeWitt metric, and (as is traditional in physics) one can ignore
the fact that the space is infinite-dimensional and use this metric
to define a measure.  Once you have one such measure, you have a
lot, since you can multiply by any reasonable positive function on
the space of geometries.  

(For anyone who wants to be picky, it is true that the DeWitt metric
is really a metric on the space of _metrics_ rather than the space
of geometries.  To get the metric on the space of geometries, you
have to "gauge-fix" and factor out the coordinate transformations.
But this is fairly standard, and in fact, unlike the rest of the
construction, can be done in a reasonably rigorous fashion, thanks
to the work of David Ebin, a mathematician who has studied the space
of geometries fairly carefully.)

Of course, the fact that the space of geometries is infinite-dimensional
does cause problems in defining these measures rigorously.  There are
a number of possible approaches.  You can approximate the smooth
geometries by flat simplicial complexes (the three-dimensional version
of the approximation of a hemisphere by a geodesic dome), for instance,
or you can define a measure by requiring that Gaussian integrals be
properly normalized.  For more formally inclined physicists like John
Baez, these procedures are not completely satisfying, but for most of
us they'll do for the moment.

Having said this, though, I completely agree with you that we have no
idea of the _correct_ measure on the space of three-geometries.  One
of the main goals of quantum cosmology is precisely to find such a 
measure.  A lot of the fine-tuning and naturalness arguments you
criticize can be translated into statements about this measure; for
instance, we would like to have it sharply peaked around geometries
for which the cosmological constant is very small (in Planck units).
There are a number of proposals for how to do this --- for instance,
Hawking's "no boundary" wave function would define a measure on
three-geometries --- but we're a long way from a believable model.

Steve Carlip
carlip@dirac.ucdavis.edu
From: firth@sei.cmu.edu (Robert Firth)
Newsgroups: sci.physics
Subject: Re: How do you draw a straight line?
Date: 6 Oct 92 12:10:36 GMT
Organization: Software Engineering Institute

In article <1992Oct6.030213.20215@galois.mit.edu> jbaez@riesz.mit.edu (John C. Baez) writes:

>The compass is nice because it works straight from the definition of a
>circle, while a ruler, as you note, is not so nice since it does not
>work from the definition of a straight line as the shortest path between
>two points.  However, there is a machine that has been built which draws
>straight lines "by definition."  Alas, I forget how it works.

Gee, we did this in school - don't they do it any more?  You draw a
straight line by taking a thread covered in chalk dust, and stretching
it between the two points.  Then snap the taut thread against the
blackboard to get a chalk line.  That "machine" does follow from the
Euclidean definition.
Newsgroups: sci.physics
Newsgroups: sci.physics
Subject: Re: Transactional interpretation of QM
From: mcirvin@husc8.harvard.edu (Mcirvin)
Date: 26 Sep 92 16:43:08 GMT

prim!dave@germany.eu.net (Dave Griffiths) writes:

>I've only skimmed through it, but it sounds like a fun idea. Basically an
>emitter sends out an "offer wave" in both time directions, and an absorber
>responds by sending back a "confirmation wave" in the reverse time direction.
>This process "continues to completion with satisfaction of quantum boundary
>conditions at emitter and absorber loci, in analogy with a standing wave
>between terminating walls".

I'd like to know what the difference is between a wave going forward and  
a wave going backward.  It seems like he's almost assuming some kind of
super-time that you can use to tell whether a wave's going "forward in
time" or "backward in time." 

It sounds to me like a fine way to think about these things if you really
must imagine measurement results causing each other along timelike
intervals.  I suspect that it's logically equivalent to a Copenhagen-
style view, though.  When you measure some observable, you select out
a final state that can be traced backward to some portion of the initial
state; that seems to me to be no different from the "confirmation wave" and
its forward-in-time transactional consequences.  It doesn't matter when
you do the projection, since time evolution is unitary.  I therefore
don't think this is any better or worse than something involving collapse,
except that it seems to involve somewhat more complicated machinery.

I suppose that showing this to be equivalent to an interpretation with
collapse would be a nice way to demonstrate that collapse has no non-
Lorentz-invariant consequences.  That sounds somewhat opposite to Cramer's
agenda, though.
-- 
Matt McIrvin, posting nonsense again 
Newsgroups: sci.physics
From: dwr2560@rigel.tamu.edu (RING, DAVID WAYNE)
Subject: Re: Spin
News-Software: VAX/VMS VNEWS 1.41    
Organization: Texas A&M University, Academic Computing Services
Date: Tue, 6 Oct 1992 01:19:00 GMT

ramsay@unixg.ubc.ca (Keith Ramsay) 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.                                 ^^^^^^
> ^^^^^^

I think he means the force is toward the retarded position.

>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.

ouch. I agree the statement is misleading. He should describe 'the manner'
to avoid confusion.

Dave Ring
dwr2560@zeus.tamu.edu



Newsgroups: sci.physics
From: jbaez@riesz.mit.edu (John C. Baez)
Subject: Re: Local expansion
Keywords: expansion, Hubble, gravity
Organization: MIT Department of Mathematics, Cambridge, MA
Date: Tue, 29 Sep 92 04:08:40 GMT

In article <1a87m0INNnu9@smaug.West.Sun.COM> Richard.Mathews@West.Sun.COM (Richard M. Mathews) writes:

>Agreed.  A good way to see this is with the picture on page 739 of Misner,
>Thorne, and Wheeler.  You don't need to understand MTW to understand
>this picture.  Replace the usual universe-is-a-balloon picture with
>one where the universe is a ball with spikes coming out of it.  Each
>spike corresponds to a gravitational well of a mass concentration.  Away
>from the concentrations, the universe is octahedral or dodecahedral or
>whatever, depending on the number of mass concentrations you use.  The
>key is that the universe is essentially flat in all the gaps.

Just to be my usual irritatingly pedantic self, I'll note that
the absence of matter does not mean zero curvature in 4d relativity.
This doesn't affect your point.  Of course the picture shows a
2d space, which would be suitable for 3d GR, where no matter means
zero curvature.  
Newsgroups: sci.physics
From: tekman@ecn.purdue.edu (Erkan Tekman)
Subject: Re: Dirty Math Joke
Organization: Purdue University Engineering Computer Network
Date: Sun, 4 Oct 1992 19:38:18 GMT


 d
 -- sin (x) = six = 6
 dn

 e^{i\pi/2} 8 = oo (infinity)

-- 
Erkan Tekman

tekman@ecn.purdue.edu
From: bweiner@ruhets.rutgers.edu (Benjamin Weiner)
Newsgroups: sci.physics
Subject: Re: STRUCTURE OF TIME
Date: 28 Sep 92 23:22:07 GMT
Organization: Rutgers Univ., New Brunswick, N.J.

> [ sarcastically ]
>So the scientists are responsible for ... the suffering av women
>who don't have to do grueling house-work because of machines ...

Or the men who don't have to do grueling house-work because of
machines.  You forgot them.
Newsgroups: sci.physics
From: daryl@oracorp.com (Daryl McCullough)
Subject: Re: I'm no radical
Organization: ORA Corporation
Date: Tue, 6 Oct 1992 03:39:31 GMT

In article <1992Oct4.223546.9969@galois.mit.edu>, jbaez@riesz.mit.edu
(John C. Baez) writes:

[stuff deleted]

Just a comment: that was a very nice essay about the nature of
progress in theoretical physics.

Daryl McCullough
ORA Corp.
Ithaca, NY

Newsgroups: sci.physics
From: hearns@vxcrna.cern.ch (HEARNS,J./EP)
Subject: Re: How do you draw a straight line?
News-Software: VAX/VMS VNEWS 1.41    
Organization: European Organization for Nuclear Research, CERN
Date: Mon, 5 Oct 1992 17:45:00 GMT

In article <1992Oct5.154211.21663@ecrc.de>, micha@ecrc.de writes...
>In article 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? What
>>defines straightness?
> 
>This is something I've been wondering about since a long time. Although we can
>make a circle as precise as we want, I think we cannot make a really
>precise straight line - every straight line is made from another one or from a tool
>that has been made using some older straight lines - so it all comes down to
>copying a line that has been made thousands years ago. Although we have precise
> 
ahem... This isnt my area of expertise,
but many surveys these days are based on straight lines defined by lasers.
Could someone from a national standards institution tell us
if there is a straight line standard based on laser light?

On another note, the gravitational wave researchers at my institution
(Glasgow University) and at other places can measure
changes in DISTANCE to quite mind--boggling accuracy using laser
light stored in cavities.
Don't have the exact number to hand, but could find out if need be.

Newsgroups: sci.physics
From: firth@sei.cmu.edu (Robert Firth)
Subject: Re: Schrodingers Dog
Keywords: Cats , Quantum Merchanics, Cruelty to Animals
Organization: Software Engineering Institute
Date: Mon, 5 Oct 1992 12:49:39 GMT

In article <1992Sep30.135833.202931@uctvax.uct.ac.za> naturman@uctvax.uct.ac.za writes:

>Physicists just don't seem to understand that probability has got to do with
>knowledge. Probabilities are not absolute but depend on the observer.

Not necessarily.  If you go up to the roulette table and bet on red, you
will win 18/37 of the time.  That has nothing to do with your knowledge
of probability, little balls, or anything else.  It has nothing ot do
with the croupier's knowledge.  That probability is objective: it is
a property of the wheel and the ball, not of any observer's state of
mind.  That probability is absolute enough to support a very large
industry.

Now replace the roulette wheel by a device that fires photons through
a polarising filter.  If you bet on H, you will win 1/2 of the time.
That probability, too, is objective: it is a property of the filter
and the photon.
From: matt@physics.berkeley.edu (Matt Austern)
Newsgroups: sci.physics
Subject: Re: Static Gravity vs. Gravitational Radiation (was Spin)
Date: 30 Sep 92 10:52:22
Organization: Lawrence Berkeley Laboratory (Theoretical Physics Group)
	<MATT.92Sep29114552@physics.berkeley.edu>
	<STEINLY.92Sep29131347@topaz.ucsc.edu>
	<1992Sep30.160233.17640@CSD-NewsHost.Stanford.EDU>
Reply-To: matt@physics.berkeley.edu
NNTP-Posting-Host: physics.berkeley.edu
In-reply-to: pratt@Sunburn.Stanford.EDU's message of Wed, 30 Sep 1992 16:02:33 GMT

In article <1992Sep30.160233.17640@CSD-NewsHost.Stanford.EDU> pratt@Sunburn.Stanford.EDU (Vaughan R. Pratt) writes:

> Hmm, this is peculiar.  My feeble Quayle's-eye view of gravity led me
> to the thought that finite propagation of gravity was only detectable
> in accelerating situations (such as two stars rotating about each
> other).  I am now hearing an equivalent statement, but expressed in
> terms of a distinction between gravitation and gravitational
> radiation. 

In both electromatnetism and gravitation, the only time you can see a
finite speed of propagation is when something is propagating---that
is, when there is radiation.

There is, however, a real difference between electromagnetism and
gravitation, which probably shouldn't be glossed over too quickly:
radiation is much more important in electromagnetism than in General
Relativity.  The (naive) way I look at it is that since there are two
different signs of electric charge, you can get electromagnetic
radiation from a time-varying dipole moment.  In the case of
gravitation, however, the lowest-order term that can produce radiation
is a time-varying quadrupole moment, which thus results in a large
suppression factor.

What this means, then, is that even in situations where something is
accelerating, the gravitational radiation that is produced may well be
either absent or very tiny.  (In the case of the Solar System, for
example, I don't think there's any hope of detecting it.)  And, again:
if radiation is completely negligible, then you're not going to see
any propagation delays.
--
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
From: scip1061@nuscc.nus.sg (Marc Paul Jozef)
Subject: Re: Understand...!!!!
Organization: National University of Singapore
Date: Thu, 1 Oct 1992 05:38:30 GMT

Physics is about properties of nature on which we all agree.
The bottom-line is common-sense intuition, not mathematics.
To emphasize this obvious fact, a long boring story follows.

`Time flows' expresses the following intuition, in which we
all *believe*: if we have a point of a material object, then
the set of events happening in that point can be linearly
labeled from `past to future' in a way that we all agree
upon (using common sense). Any device that sepatates the
`different' events (common sense again) by correctly ordered
labels is called a clock.
If one has some material coordinate grid (x,y,z), and one has
clocks in each point, it follows that each event happening
in the grid gets a unique label (t,x,y,z).

Now comes the mathematical *idealization* of that intuition:
Forget about the fuzziness of the intuitive concepts `point'
and `event'. View the grid as a continuum, and t as a contin-
uous parameter in each grid-point. We then *believe* that we
will be able to cover all of spacetime whith such local
coordinate-patches, such that these patches relate differentiably.
i.e. we believe that spacetime can be given the structure of
a manifold. The intuition above tells us that each point in
a material grid describes an `oriented curve' in spacetime.
To give this rigorous meaning, one can use a Lorentz metric
on spacetime to define `time-orientability' precisely.
And blah blah blah.

Bottomline (as promised) : First intuition, the n mathematics
(and with the mathematical results, back to intuition; if 
you can't, you've waisted your *time*, just like I've been
doing now).

marc.
Newsgroups: sci.physics
From: palmer@sfu.ca (Leigh Palmer)
Subject: Re: Thermo question for you
Organization: Simon Fraser University
Date: Fri, 2 Oct 1992 18:52:57 GMT

I don't like the idea of refering to the "entropy of a microstate" very much.
The entropy of a system which is constrained to be in a microstate such as you
describe is, formally, k ln 2 if the "spheres" are indistinguishable particles
with no internal degrees of freedom and I can similarly simplify all other
aspects of the system. I am most distressed by the idea of applying the entropy
concept to a two-particle system. Why on Earth would anyone ever want to do
that? Surely no physical result can be inferred from consideration of such a
system. Are we discussing physics here? 

Leigh
Newsgroups: sci.physics
From: crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass)
Subject: Re: Mattel protest
Organization: University of Virginia
Distribution: usa
Date: Tue, 6 Oct 1992 06:40:53 GMT

In article <1992Oct6.031556.20357@galois.mit.edu> jbaez@riesz.mit.edu (John C. Baez) writes:
>
>>     I take it then that y'all did not find math to be tough?
>>
>>                               dale bass
>
>No.  Honest, most things in life are more tough for me than math.
>I can just imagine more realistic Barbies:

     There are the odd exceptions (no pejorative implied).

     I, as well, do not find math to be the most difficult aspect
     of existence.  However I have, on occasion, encountered those that do.
     I have a sneaking suspicion that the difficulty did not involve
     the oppression of society expressing itself in the synthesized
     guise of a plastic nimnull.

>"Getting enough money to put a down-payment on a house these days is tough!"
>"Dealing with my personality differences with Ken is tough!"
>"Reconciling quantum theory and general relativity is tough!"
>"Facing up to my mortality and existential angst is tough!"

     Or how's about "Facing up to reconciling getting relative personality
     angst with general existential morality is tough, especially in 
     a quantal house with Ken."

     That's probably one reason why Mattel didn't ask me.

                            dale bass
-- 
C. R. Bass                                           crb7q@virginia.edu
Department of Mechanical and Aerospace Engineering
University of Virginia
Charlottesville, Virginia                            (804) 924-7926
From: sichase@csa3.lbl.gov (SCOTT I CHASE)
Newsgroups: sci.physics
Subject: Re: Nuclear equations
Date: 4 Oct 1992 12:04 PST
Organization: Lawrence Berkeley Laboratory - Berkeley, CA, USA
Distribution: world
NNTP-Posting-Host: 128.3.254.198
News-Software: VAX/VMS VNEWS 1.41    

In article <1992Oct2.230447.25257@access.usask.ca>, choy@skorpio.usask.ca (I am a terminator.) writes...
>What do we know for closed form equations describing or modelling
>the activity experienced by subatomic particles? How about recursive
>equations or series? Do we tend to talk about collections of
>particles or can we talk about each individual particle as it
>interacts with other particles? Can we predict what happens at
>a particular point in space as time passes? I'm wondering about the
>extent of any generalization that has been done from experimental
>results. Is there a handbook of formulas available? in the works?
>Anyone interested in compiling one?
> 
>Henry Choy
>choy@cs.usask.ca

My goodness.  What a pile of questions!  It seems like you are asking
if particle physics exists as a theoretical science, to go along with 
the piles of data we have acquired over the years.  The answer, of course,
is yes.  Rather than try to answer each of your questions point by point,
I will recommend that you pick up any of the common undergraduate introductions 
to particle physics and do a little casual study.  One good book is 
Perkins.  I never can remember titles, only authors.  I think that it's
_Introduction to High Energy Physics_.  Good luck.

-Scott  
--------------------
Scott I. Chase			"The question seems to be of such a character
SICHASE@CSA2.LBL.GOV		that if I should come to life after my death
				and some mathematician were to tell me that it
				had been definitely settled, I think I would
				immediately drop dead again."      - Vandiver
Newsgroups: sci.physics