HDTenEightyP/NetNews huggingface dataset:
From: carlip@landau.ucdavis.edu (Steve Carlip)
Newsgroups: sci.physics
Subject: Re: What is the Speed of Gravity - A Call for a Volunteer
Date: 1 Oct 92 23:48:15 GMT
Organization: Physics, UC Davis

In article <1992Oct1.020651.10696@nuscc.nus.sg> matmcinn@nuscc.nus.sg (Mcinnes B T (Dr)) writes:
>[...]
>I hope that the eventual entry will discuss what happens when the
>gravitational waves are propagating in a background which is not
>approximately flat. Does "gravity" propagate at the speed of light near
>a black hole?

For a partial answer, see chapter 35.13 of Misner, Thorne, and Wheeler,
``The Shortwave Approximation.''  To answer this question, you need to
assume that
(1)  the amplitude of the gravitational wave is small; and
(2)  the wavelength of the gravitational wave is short compared to the
     radius of curvature of the background.
Without assumptions like these, the nonlinearities make things too hard
--- you'll have a hard time defining the ``wave'' as something distinct
from the ``background.''  With these assumptions, the answer is basically
that a gravitational wave moves at the local speed of light, as set by
the background spacetime, but with slightly different interactions with
the background geometry (rotation of the polarization, backscatter from
background curvature).  (See exercize 35.15 for ``geometric optics''
for gravitational waves.)

Steve Carlip
carlip@dirac.ucdavis.edu
From: matt@physics.berkeley.edu (Matt Austern)
Newsgroups: sci.physics
Subject: Re: Spin
Date: 29 Sep 92 15:45:52 GMT
	<1992Sep29.065640.18839@CSD-NewsHost.Stanford.EDU>
	<STEINLY.92Sep29105205@topaz.ucsc.edu>
Reply-To: matt@physics.berkeley.edu
Organization: Lawrence Berkeley Laboratory (Theoretical Physics Group)
NNTP-Posting-Host: physics.berkeley.edu
In-reply-to: steinly@topaz.ucsc.edu's message of 29 Sep 92 10:52:05

In article <STEINLY.92Sep29105205@topaz.ucsc.edu> steinly@topaz.ucsc.edu (Steinn Sigurdsson) writes:

> Figured I might as well interject at this point.
> Tom? You lurking there waiting to pounce??? ;-)
> The "gravity" from each component in a binary star does
> not arrive delayed, see for example LPPT 12.4 and MTW 18.4 and 39.9,
> especially eqn 39.64

I know I've said this before, but I may as well say it again: I think
we're begin confused over semantics; we have to be careful over what
it means to talk about the speed of propagation of gravity.

I contend that in a static situation (i.e., one where there is no
gravitational radiation), it is meaningless to talk about the speed of
propagation of gravity, since nothing is propagating.  I contend,
then, that detecting a finite speed of gravitation is equivalent to
detecting the effects of gravitational radiation.

And, as is well known, this has been done in the case of binary
neutron star systems.  The effects of radiation show up in (if I'm
remembering right) the post-post-post-Newtonian approximation, and
they have been observed.
--
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!
From: lnh@soliton.physics.arizona.edu (sometimes a Wombat)
Newsgroups: sci.physics
Subject: Re: TIME HAS INERTIA
Date: 25 Sep 92 21:15:54 GMT
Organization: Society for the Appreciation of Janni Lee Simner

Alexander Abian claims:
>      
>         TIME HAS INERTIA AND SOME ENERGY IS IRRETRIEVABLY DISSIPATED
>                          ON MOVING TIME FORWARD

In addition to the other problems (such as this implying time is not
invarient, and total lack of reason to belive this) that others have 
brought up:

>(2)   E = mcc  (Einstein)   may be replaced by   E = m exp(-At)  (Abian)

c^2 is a conversion factor for units.  Exp is unitless.  Huh?

>  The Universal time is obtained by taking the natural log from both sides of 
>(1) as:
>
>(3)   t = (1/A) log (B/E(t))   

This "universal" time has no meaning as such if A is not a constant in 
time.

	Larry "Wierdness of the cosmos" Hammer
--

LNH@physics.arizona.edu          \  "What can be seen, heard, and learned, 
The insane don't need disclaimers \  this I prize." -- Heraclitus, #13
Newsgroups: sci.physics
From: jbaez@riesz.mit.edu (John C. Baez)
Subject: Re: Spin
Organization: MIT Department of Mathematics, Cambridge, MA
Date: Tue, 29 Sep 92 18:40:16 GMT

In article <1992Sep28.221735.35@sjsumcs.sjsu.edu> b5249-23@mathcs.sjsu.edu (Kurt Stocklmeir) writes:
>Robert Firth
> His article
>
>Some other people have confused you.  Look at Gravitation
>Misner, Thorne, Wheeler P.177.  There are also some other parts
>of the book that include the area of gravity having an infinite
>velocity.

>Physics teachers give hours of homework problems to physics students and
>because of that physics students do not ever have time to learn
>anything about physics.  That explains why John Baez and others
>do not know and can not figure out P.177.  

Why, 'cause I'm too busy grading the resulting masses of homework?

>The only thing that was meant on P.177 was that gravity travels
>faster than the speed of light.  But in relativity, nothing
>travels faster than the speed of light.  That means any gravity
>moving faster than the speed of light does not fit into relativity.

No, it says that Newtonian gravity travels at infinite speed,
hence is inconsistent with relativity.  That's why Einstein invented
a BETTER theory of gravity in which gravity DOES move at the speed of
light.  It's called general relativity.

(I'm beginning to like these capital letters!)

>For example, the direction of gravity from the sun to the Earth is
>straight to the Earth.  The direction of light from the sun to the
>Earth is not straight from the sun.  Therefore, gravity moves faster
>than light.  The Earth orbits the sun.  The Earth does not orbit
>the place where light from the sun is coming from.  If it tried, the Earth
>could not orbit the sun.  The same is true for galaxies.  Stars
>orbit the same place in a galaxy.  This is associated with a center of
>mass.  I do not think I need to tell you how long it takes light
>to travel through a galaxy.  If gravity travels at the speed of light
>there would not be any stars in a galaxy.  If there were any stars,
>they would all be orbiting different places.

This apparent paradox has recently been explained for the nth time here
on sci.physics.

>Paul Davies said that imaginary forces have an infinite velocity.

Yes, and imaginary people drive imaginary cars at infinite velocity.

>Gravity that is observed can not fit into relativity.  That is what
>is meant on P.177.  

Bull-oney!  The whole friggin' book is about how one fits gravity into
relativity.  That's what general relativity is about.  Try reading the
whole book, not just a couple of sentences taken out of context.

Newsgroups: sci.physics,sci.astro,sci.math,sci.philosophy.tech
From: crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass)
Subject: Re: STRUCTURE OF TIME
Organization: University of Virginia
Date: Sat, 3 Oct 1992 20:37:10 GMT

In article <1992Oct02.130413.22524@dlogics.com> trr@dlogics.com (Tim Ringwood) writes:
>
>Two views on these wonderful post that are feeled with such love. NOT!
>
>1. One who feel they must spout of their belief in a place where it
>   does not belong, (this is MATH not RELIGION) is either arrogant or
>   a fool.
>
>2.  I strongly feel that those who belive in God due so because of 
>    their own insecurity to deal with life as it is.  (Kind of link
>    a lonley kid's pretend friend. ) If you need help with your insecurities 
>    go to a shrink, and stop cluttering up this news group.

     Can we stop insulting other's religions (or religion in general)
     in these forums?   It invites negative commentary on the pursuits
     of physics, math, and astronomy which have nothing to do with 
     physics, math and astronomy.

                               dale bass
-- 
C. R. Bass                                           crb7q@virginia.edu
Department of Mechanical and Aerospace Engineering
University of Virginia
Charlottesville, Virginia                            (804) 924-7926
Newsgroups: sci.physics
From: sarfatti@well.sf.ca.us (Jack Sarfatti)
Subject: Quantum Nights 1
Organization: Whole Earth 'Lectronic Link
Date: Thu, 1 Oct 1992 04:05:45 GMT


Night Thoughts of a Quantum Mechanic in the style of Ludwig Wittgenstein. 1

An electric charge is freely falling. A photon detector is freely falling.
The freely falling detector will not detect real photons from the freely
falling charge.

If the detector is at rest relative to the mass source of the gravitational
field it will detect photons from the freely falling charge. The detector
is no longer freely falling it is no longer in an inertial frame if it is
at rest in the gravitational field.

The detector at rest will not detect photons from a charge at rest in the
gravitational field.

However, a freely falling detector will detect photons from a charge at
rest in a gravitational field.

Classically, an accelerating charge radiates energy and slows down
(radiation arrow of time). Quantum mechanically an electron in an energy
eigenstate does not radiate - until it quantum leaps. Once can picture
destructive interference between advanced incoming and retarded outgoing
photons in the stationary electron state. When this destructive
interference shifts, there is a quantum jump induced from the future.  Is
this consistent with Bohm's quantum potential picture which says that an
electron stands still in the S state of hydrogen.
Newsgroups: sci.physics
From: dooley@helios.physics.utoronto.ca (Kevin Dooley)
Subject: Re: Mattel Protest
Keywords: So What?
Organization: University of Toronto Physics/Astronomy/CITA
Date: Mon, 5 Oct 1992 14:16:45 GMT

In article <stone.718289960@cwis> stone@cwis.unomaha.edu (Travis Stone) writes:
> ...
>Mattel may be doing the nation's kiddies a service
>by protecting their fragile self-esteem.
>...
>See? A little good can come out of every dark situation, nicht?...
>

NICHT!  This is a very bad thing!  Kids do badly in math not because
it is hard, because it isn't, but rather because they perceive it as
hard.  This is especially true with girls who are repeatedly told that
they should not be good at math or science courses because their brains
don't work that way.  Nothing could be farther from the truth.  Let's
not permit marketing idiots to create yet another generation of math
anxiety and women who believe that they are somehow inferior!

Kevin

Newsgroups: sci.physics
From: abond@rvgs.vak12ed.edu (Andrew H. Bond)
Subject: philisophical joke
Organization: Virginia's Public Education Network (Roanoke)
Date: Fri, 02 Oct 92 04:16:05 GMT

	Since people have been posting math jokes to
sci.physics, I guess phil. jokes should be o.k. too.

	A famous philosopher walks into a bar.
 The bar-tender asks, "would you like a beer?"
 The philosopher replies, "I think not," and vanishes.
			AHB :-)
-- 

		Andrew H. Bond

			no matter how bad the election gets remember:
From: burton@cfm.brown.edu (Joshua W. Burton)
Newsgroups: sci.physics
Subject: Re: Question about electron spin
Date: 30 Sep 92 12:52:41 GMT
Organization: Brown University Center for Fluid Mechanics
NNTP-Posting-Host: qcd2.het.brown.edu

One caveat about applying `polarizer intuition' to electron spins:  you must
remember that the two independent `polarizations' of a spin-1/2 particle are
180 degrees apart, not 90.  If you want to see electrons that were spin-up in
the Z direction become spin-down, here's what you do:

1.) Measure their Z-spin (Stern-Gerlach apparatus) to ensure you have a beam
    of pure spin-up electrons;

2.) Put this beam through a perpendicular apparatus, measuring their X-spin.
    Half of the beam will be spin-left, and the other half spin-right, of
    course.

3.) Now run either beam through a second Z-spin apparatus, and you will find
    that half of the electrons are now spin-down, not spin-up.  Of course, a
    *close* examination of the angular momentum of the apparatus will tell
    you where the Z-spin disappeared to.

Leave out step 2, of course, and you will never see a spin-down electron at
step 3.  This is indeed just like what happens to photons, except that there
(since a photon has spin 1) the independent states are vertical and horizontal
polarization---only 90 degrees apart---and the intermediate step that allows
light to pass through crossed polarizers is at 45 degrees.

The rule that `rotational angle between orthogonal spin states is 90 degrees
divided by the spin of the particle' applies to gravitons as well, by the way.
If you aim a small graser (Spectra-Physics catalog, August 2291; I'll look
up the part number for you, but it will take a while) at a + polarizer, and
then an x polarizer, you will find that no gravitons get through.  If you
interpolate a `halfway' polarizer, twisted 22.5 degrees to the right, then
a quarter of the gravitons will sail right on through, even though the + and
x states, 45 degrees apart, are orthogonal.

What about gravitinos (hypothetical spin-3/2 particles)?  Well, my dissertation
is (loosely) about them, so I should be the right person to ask, but damfino.
Gravitinos are usually dealt with in quantum field theory by thinking of them
as `vectors of spinors', a rather adhoc way of applying what we think we
understand about spin-1 and spin-1/2 to a particle that has attributes of both.
It works just fine for calculating amplitudes of fundamental processes, and
supergravity even helps us get a handle on the divergences...but my intuition
about their Lorentz-group behavior is weak.  Hannu?




-- 
Stadium sedipilae opt- |======================================================
imum Saeptum Paludosum | Joshua W. Burton  burton@het.brown.edu  (401)351-5908
etiamnunc est. Ain tu? |======================================================
From: bweiner@ruhets.rutgers.edu (Benjamin Weiner)
Newsgroups: sci.physics
Subject: Re: Are redshifts discrete?
Keywords: autocorrelation
Date: 2 Oct 92 20:43:22 GMT
Organization: Rutgers Univ., New Brunswick, N.J.

Joe Keane writes:
>Well, it seems that everyone took the opportunity to show how you can't have
>all the redshifts be perfectly quantized for all observers.  But that's not
>what was being claimed!  What they said is that there are peaks in the power
>spectrum.

Are you sure?  Broadhurst et. al.'s Nature paper is about peaks in
the power spectrum, but that's not what I was talking about, as I
tried to make clear some time ago.  Tifft and company (papers in the
Astrophysical Journal) seem to claim that there are exactly 
quantized redshifts in units of 12.07 km/s.  

> ... if your lattice has spacing 1/f, you
>will also get frequency peaks at f/sqrt(2) and so on.

I know this.  I'm not sure what Tifft thinks, 'cause he doesn't
do irrational multiples (that's the "quantization").  At least, so
it seems; his papers are none too clear.

>Having said that, i think the claimed peaks probably don't exist.

I heard from a friend that somebody, he can't remember who, says the
Broadhurst result goes away if you do different binning.  I think
there is unspoken agreement that the Tifft results are not worth
spending time worrying about.
From: ap1i+@andrew.cmu.edu (Andrew C. Plotkin)
Newsgroups: sci.physics
Subject: Re: How do you draw a straight line?
Date: 6 Oct 92 11:38:19 GMT
Article-I.D.: andrew.AeoSgfK00gpIE0zY4j
	<1asiu6INNf5k@agate.berkeley.edu>
Organization: School of Computer Science, Carnegie Mellon, Pittsburgh, PA

Excerpts from netnews.sci.physics: 6-Oct-92 Re: How do you draw a
strai.. Aephraim Steinberg@physi (694)

> (Besides, if the string has any mass and is in any gravitational field
> whatever, then any finite tension will still leave it a catenary, just
> a straighter and straighter one.  I believe the question was one of
> principle.)

Nope. Stretch it vertically. 

You still need a perfectly spherical planet, or at least one with the
appropriate symmetry around where you're doing the experiment.

A laser in a vacuum should also be counted as a straight line,
regardless of the gravitational field. It follows a geodesic, and what
does "straight" mean if not a geodesic? :-)

--Z

"And Aholibamah bare Jeush, and Jaalam, and Korah: these were the borogoves..."
Newsgroups: sci.physics
From: tolman%asylum.cs.utah.edu@cs.utah.edu (Kenneth Tolman)
Subject: Number of elementary particles in visible universe?
Date: 5 Oct 92 01:00:24 MDT
Organization: University of Utah, CompSci Dept

What is the approximate number of elementary (I mean proton, electron,
neutron) particles in the visible universe?  Is it around 10^40, or 
way higher?  

Newsgroups: sci.physics
From: scip1061@nuscc.nus.sg (Marc Paul Jozef)
Subject: Re: Expansion
Organization: National University of Singapore
Date: Thu, 1 Oct 1992 04:04:33 GMT

Dave's question touches one of the most puzzling
problems in cosmology. Measurements of the relation
optical size-redshift of distant galaxies indicate that,
if the standard global model is correct,
galaxies have *grown* in size over the years.

According to Sandage (1988 or 1990), this observation
raises the most serious doubt to date about the
standard-model.
Curiously, the data are consistent with the static
universe of the tired-light theories. (see sandage)

marc.


Newsgroups: sci.physics
From: firth@sei.cmu.edu (Robert Firth)
Subject: Re: Understand...!!!!
Organization: Software Engineering Institute
Date: Wed, 30 Sep 1992 12:03:09 GMT

In article <1992Sep30.073018.13232@nuscc.nus.sg> 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.

An interesting clock.  And you're right: numerous experiments have
shown that psychological time is closely correlated with metabolic
rate.  If you shut people up in caves, for instance, their circadien
rhythm will drift, and after a week or so they will indeed start
measuring time in terms of hunger, or fatigue.

The effect is far more pronounced in animals that are not endothermic.
There is an almost exact relationship between the chirp frequency of
a cricket and the ambient temperature.  In the tropics especially,
the slowdown during dusk is remarkable.

The point of this being, that in default of any better clock, a race
of intelligent crickets would perceive the night as lasting a lot
longer than the day, which would make for some interesting astronomy.
And for us, since "worldlines" are imperceptible (indeed, I might
even call them mathematical fictions, but we know that only quantum
mechanics has mathematical fictions) we need some operational means
of determining the vales of the time coordinates in our equations.

Those means are clocks, and it always makes sense to ask how good our
clocks are, and what unknown influences might be perturbing them.
From: sichase@csa2.lbl.gov (SCOTT I CHASE)
Newsgroups: sci.physics
Subject: Re: TIME HAS INERTIA, ALTERING THE ORBIT OF VENUS AND THE TILT OF EARTH
Date: 6 Oct 1992 15:16 PST
Organization: Lawrence Berkeley Laboratory - Berkeley, CA, USA
Distribution: world
NNTP-Posting-Host: 128.3.254.197
News-Software: VAX/VMS VNEWS 1.41    

In article <abian.718392970@pv343f.vincent.iastate.edu>, abian@iastate.edu (Alexander Abian) writes...
>   I received many anonymous telephone calls in strong and fervid support 
>of my proposals: blah blah blah...
>   The callers feel that the current explanations of the nature of TIME 
>(various variations on the Space-Time Riemannian Manifold-themes) are total-
>ly  unconvincing and unsound.  They feel that my proposals are sound, con-
>vincing, cogent and realistic.
>   The anonymity of the callers is understandable.  Association with 
>radically bold and dauntless ideas is very often treated as an act of
>recusancy (recall that Copernicus, Galileo and many others were silenced
>and subject to a great deal of hardship for their bold and intrepid ideas).
>                                                 Alexander ABIAN

Beware of the physics mafia.  They are out to control society through the
control of the physical world.  Already, they have prevented generations of
otherwise ambitious and adventurous souls from travelling faster than the 
speed of light.  Who knows where it will stop?  By keeping the secrets 
of the Inertia of Time, Biological Transmutations, Neutrino Souls, patented
Antigravity machines, the great Larson (peace be with him!), and the 
fatal and obvious flaws that would destroy quantum mechanics and special
relativity, all to themselves, they are seeking to ruin humanity and 
take total control of our lives.  

I even know who they are.  But if I told you, I would have to kill you.

-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
Xref: sparky sci.physics:15987 sci.astro:10435 sci.math:12757 sci.philosophy.tech:3561
From: rah@public.BTR.COM (Richard A Hyde  rah@btr.com)
Newsgroups: sci.physics,sci.astro,sci.math,sci.philosophy.tech
Subject: Re: Hannu is a wood-duck
Date: 6 Oct 92 02:28:01 GMT
Followup-To: sci.physics
Organization: BTR Public Access UNIX, MtnView CA. For info contact: info@BTR.COM

Why is it an insult to call someone a "wood-duck"?  What *is* a wood-duck?
Is it, perhaps, a foreign locution?


-- 
------------------------------------------------------------------------------
|   Richard Hyde  |  RaH@btr.com  |    This space intentionally left blank   |
------------------------------------------------------------------------------
Newsgroups: sci.physics
From: crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass)
Newsgroups: sci.physics,sci.astro,sci.math,sci.philosophy.tech
Subject: Re: STRUCTURE OF TIME
Date: 4 Oct 92 16:13:48 GMT
Article-I.D.: murdoch.1992Oct4.161348.17726
Organization: University of Virginia

In article <1992Oct4.122333.1@tnclus.tele.nokia.fi> hporopudas@tnclus.tele.nokia.fi writes:
>
>In article <1992Oct3.011338.4175@murdoch.acc.Virginia.EDU>,
>crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass) writes:
>> In article <1992Oct2.230052.25196@hpcvaac.cv.hp.com>
>billn@hpcvaac.cv.hp.com (bill nelson) writes:
>>>kim@Lise.Unit.NO (Kim Gunnar St|vring yhus) writes:
>>>:  >
>>>:  >   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.
>>>
>>>Not surprising, when much of the Bible teaches fear of God. How can you be
>>>truly happy when you are in constant fear of an omnipotent being who may,
>>>out of whim, strike you dead without warning and send you to a place of
>>>perpetual suffering called Hell?
>>>
>>>Bill
>>
>>     I think you'll find that if you do not use this forum to
>>     misinterpret and criticise religion, then it will be easier to keep
>>     religion out of this forum.  Physics has nothing to say about
>>     morality or religion and vice versa.
>>
>>                               dale bass
>
> You should say that you has nothing to say about morality.? Then why
> you then make these stupid comments. ?
>
>    ---Hannu.

    Oh Hannu, this is most unbusinesslike.  

                               dale bass

-- 
C. R. Bass                                           crb7q@virginia.edu
Department of Mechanical and Aerospace Engineering
University of Virginia
Charlottesville, Virginia                            (804) 924-7926