HDTenEightyP/NetNews huggingface dataset:
From: steinly@topaz.ucsc.edu (Steinn Sigurdsson)
Newsgroups: sci.physics
Subject: Re: Black hole insights
Date: 24 Jan 93 15:15:39
Organization: Lick Observatory/UCO
NNTP-Posting-Host: topaz.ucsc.edu
In-reply-to: brahm@cco.caltech.edu's message of 24 Jan 1993 07:06:04 GMT

In article <1jtf4sINNrcd@gap.caltech.edu> brahm@cco.caltech.edu (David E. Brahm) writes:

   bbowen@megatest.com (Bruce Bowen) writes re: an uncharged, non-rotating
   black hole,
   > The coordinate time for an infalling infinitesimal testpoint to reach
   > the horizon is infinite.  The proper time is finite.

   I've been trying to get this straight too, so someone let me know if I'm
   mistaken, but I think your first statement is only true in some coordinate
   systems (e.g. Schwarzschild coordinates), not in others (e.g. ingoing
   Eddington-Finkelstein coordinates).  See MTW pp. 828-829, 872-875.

   What I want to know is, when people calculate how much "time" it takes for
   a black hole to evaporate (proportional to M^3 they say), what coordinate
   are they talking about?  I'm still confused by the fact that a test
   particle takes infinite Schwartzschild "t" to pass the horizon, but the
   hole evaporates in finite "t", and I'm not convinced that the "bulging"
   effect people have mentioned is the answer.  Perhaps I'm just being
   irresponsible using Schwarzschild coordinates when M is changing.

The Membrane Paradigm by Thorne et al discusses these issues nicely,
the formalism is ugly but it is a nice way to consider some of these 
problems, in particular it side-steps the question of what happens at
the singularity and the adding of particles to black holes as they
evaporate. Oh, for those in the mood for a challenge, it does consider
non-symmetric infall onto rotating holes :-)

I think it is very important to forget about "test" particles being
sent in carrying no mass-energy, if you want to track the fate of the
particle it has to carry _finite_ energy. Yet again QM comes to the
rescue of GR!

*  Steinn Sigurdsson   			Lick Observatory      	*
*  steinly@lick.ucsc.edu		"standard disclaimer"  	*
*  The laws of gravity are very,very strict			*
*  And you're just bending them for your own benefit - B.B. 1988*

Newsgroups: sci.physics
From: mkagalen@lynx.dac.northeastern.edu (michael kagalenko)
Newsgroups: sci.physics
Subject: Re: ATOMS & ELECTRONS
Date: 24 Jan 93 21:44:44 GMT
Organization: Northeastern University, Boston, MA. 02115, USA

In article <24JAN199310104129@csa1.lbl.gov> sichase@csa1.lbl.gov (SCOTT I CHASE) writes:
>In article <1993Jan23.220138.15459@lynx.dac.northeastern.edu>, mkagalen@lynx.dac.northeastern.edu (michael kagalenko) writes...
>> 
>>Why Earth is not crushing into the Sun ? Your answer really applys to
>>the question "Why electron in the ground state doesn't radiate"  
>
>Completely untrue.  The Earth probably has a net charge (does anyone have
>any idea what it is?), as so *does* radiate EM radiation due to it's 
>acceleration in it's orbit around the Sun.  However, the rate is probably
>completely negligible compared to other dissipative effects due to tidal
>stresses, etc.
>
>-Scott

I agree, but it's not the point.
Newsgroups: sci.physics
From: metares@well.sf.ca.us (Tom Van Flandern)
Subject: Re: The Big Bang Never Happened
Organization: Whole Earth 'Lectronic Link
Date: Fri, 22 Jan 1993 16:13:44 GMT


buell@phyast.nhn.uoknor.edu (Jim Buell) writes:

> How thick is your ISM? Does its density eventually drop off somewhere?

     The density of the ISM drops to near zero at the border of the local
superbubble, which surrounds us with a radius of a couple hundred parsecs.
Just outside the superbubble the ISM must be bunched up thicker than
average, because the contents of a sphere with about 200 pc radius has been
emptied and pushed out that far.  The density again drops to near zero at
the edges of the galaxy.  In between, it is the normal ISM we see absorbing
starlight.  -|Tom|-

-- 
Tom Van Flandern / Washington, DC / metares@well.sf.ca.us
Meta Research was founded to foster research into ideas not otherwise
supported because they conflict with mainstream theories in Astronomy.
From: bweiner@ruhets.rutgers.edu (Benjamin Weiner)
Newsgroups: sci.physics
Subject: Re: Trouble understanding bra-ket notation
Date: 22 Jan 93 01:42:42 GMT
Distribution: usa
Organization: Rutgers Univ., New Brunswick, N.J.

ask@ucscb.UCSC.EDU (Andrew Stanford Klingler) writes:

>quantities mean, I find it helpful to think of the inner product.  When
>you hear "The probability is the square of the amplitude" you're thinking
> <a|a> = |a|^2 is the probability or density.  ...

Actually, <a|a> = |a|^2 is the squared norm (length) of the vector |a>.
In order to get a probability amplitude, you need to put the vector
together with (another) state vector.  I am sorry to pick this nit,
but this was something that S*rf*tti gave us much grief by
misunderstanding.  The rest of this is directed to the original poster:

For example, 

<psi|x> , which is what is written psi(x) in intro modern physics texts,

is the probability amplitude of finding a particle in state psi at
position x.  The probability density is <psi|x><x|psi>, i.e.
|<psi|x>|^2 
The probability of finding the particle between x and x + dx is

  P(x,x+dx) = |<psi|x>|^2 dx = <psi|x> <x|psi> dx

A properly normalized state |psi> has norm 1, so <psi|psi> = 1.
The particle should be somewhere between -infinity and +infinity,
i.e. it is certain (probability = 1) that it is _somewhere_, so the 
total probability should be 1:

                 +inf
                /
P(-inf,+inf) = |  <psi|x> <x|psi> dx  = 1
              /
              -inf

                            /
You see that I inserted a  |   |x><x|   dx    into the middle of <psi|psi>
                          /

(where the integral is understood to be over all possible values of x,
in this case -inf to +inf) without changing the value.  This is known
as expanding in the basis "x".  I could equally well have expanded in
the basis "p", where p is the momentum of the particle.  In some cases
there are discrete bases, such as photon polarization, where vertical 
and horizontal form a complete basis - in this case you sum over the
basis rather than integrating.  Which basis you use is a matter of
convenience - whatever helps you get the problem done.
From: jbaez@riesz.mit.edu (John C. Baez)
Subject: Re: Questions on:  Black-Hole Thermodynamics
Organization: MIT Department of Mathematics, Cambridge, MA
Date: Mon, 25 Jan 93 00:16:04 GMT

In article <1993Jan23.231742.26244@newstand.syr.edu> rbsalgad@rodan.acs.syr.EDU (Rob Salgado) writes:
>REFERENCES would be greatly appreciated.

>4) What is the status of the cosmic censor conjecture?

Here I'd recommend the review article On Uniqueness in the Large of
Solutions to Einstein's Equations ("Strong Cosmic Censorship") by my
firend Piotr Chrusciel, in Contemporary Mathematics 132 (1992), p. 235.
From: baez@guitar.ucr.edu (john baez)
Newsgroups: sci.physics
Subject: Re: Super-Strings
Date: 26 Jan 93 04:58:23 GMT
Organization: University of California, Riverside

In article <1k09cpINNsg7@gap.caltech.edu> brahm@cco.caltech.edu (David E. Brahm) writes:
>lordSnooty@cup.portal.com (Andrew - Palfreyman) writes:
>> I wonder if the fad with string theory and superstrings is simply
>> Occam's Razor in action, or is it perhaps something at a deeper
>> level? I mean that one could just as easily have chosen a primitive
>> of higher dimensionality.
>
>One could, and people do ("super-membrane theory"), but there is something
>particularly nice about 1+1 dimensions (the world sheet of a string),
>called (I believe) conformal invariance. 

Yes, people have studied "p-branes," but they are supposedly much less
well-behaved; when you quantize them they give infinities that people
apparently have not been able to renormalize away.  

Also: the world sheet of a string is not just 2-dimensional, it's a 
Riemann surface.  This is where the conformal invariance comes in.  Recall
how in E&M you used conformal invariance of 2d electrostatics to solve
the Laplace equation with weird boundary conditions?  You were tapping
the power of the conformal group, which is infinite-dimensional in 
the 2d case.  There is so much powerful mathematics associated with
Riemann surfaces that it is natural to want to use it... and this is
what people have done (greatly pushing forward the subject in the
process).   Of course, it's not clear whether Nature finds this mathematics
as tempting as we do.
From: corleyj@helium.gas.uug.arizona.edu (Jason D Corley )
Newsgroups: sci.physics
Subject: Re: female mentors in science
Date: 28 Jan 93 00:47:12 GMT
Organization: University of Arizona, Tucson

In article <1993Jan27.210411.8122@lynx.dac.northeastern.edu> mkagalen@lynx.dac.northeastern.edu (michael kagalenko) writes:
>In article <1993Jan27.055231.23117@nuscc.nus.sg> scip2124@nusunix1.nus.sg (MARC PAUL JOREF VAN LOO) writes:
>>michael kagalenko (mkagalen@lynx.dac.northeastern.edu) wrote:
>>
>>: All this talk about "female science" looks suspiciously similar to 
>>: other well known distinctions : "Ariahn" vs "Non-Ariahn", "proletarian"
>>: vs "bourgeous" science....
>>
>>    Are you a nut?
>>
>Are you PC ?

Are you working on a PC?

--
******************************************************************************
"Every normal man must be tempted at times to spit upon his hands, hoist the
 black flag and begin slitting throats."---------H. L. Mencken
Jason D. "corleyj@gas.uug.arizona.edu" Corley Claims Full Responsibility
From: bweiner@ruhets.rutgers.edu (Benjamin Weiner)
Newsgroups: sci.physics
Subject: Re: Super-Strings
Date: 25 Jan 93 05:05:50 GMT
Organization: Rutgers Univ., New Brunswick, N.J.


 adawal@scorch.apana.org.au (Adam Walsh) writes...
>Pardon My ignorance but what is a Super String?

A SuperString is made out of the same material as a SuperBall, those
cute little bouncy things.  Physics graduate students who know that
the first problem in the _Princeton Problems in Physics_ is about a
SuperBall will no doubt be happy to hear that the first problem in the
forthcoming second edition is about a superstring ...

OK, dumb jokes aside, superstrings are a candidate for a theory that
explains, more or less, all the fundamental interactions of physics;
a reference at a popular level is the book "Superstrings: A Theory of
Everything?"  The "string" part is that these theories consider 
fundamental particles to be strings rather than points, with the
dimension of the string being incredibly small; the theory is often
characterized as having a lot of dimensions with the extra dimensions
being "rolled up," leaving only the 3+1 of ordinary spacetime.  It has
the attraction of maybe being the Big Mama of particle theory that
finally explains it all, but it is fiendishly complicated.

The "super" part is something called supersymmetry, which is popular
in "everyday" particle physics as well; in it, there is a symmetry
between fermionic (loosely, particles like quarks and electrons; the stuff
of ordinary matter) and bosonic particles (loosely, particles that 
carry the interactions/forces, like the photon).  So each fermion
has a boson partner, and vice versa.  No such partner particles have yet 
been discovered, though.

I hope this has been informative and not misleading, because
string theory is "not my department."  (inside joke, sorry)
Newsgroups: sci.physics
From: wtyler@adobe.com (William Tyler)
Subject: Re: New Physics, Healing, Paranormal
Followup-To: sci.physics
Summary: CRAP
Organization: Adobe Systems Inc., Mountain View, CA
Date: Tue, 26 Jan 1993 21:09:04 GMT

In article <1k436cINNfe5@emx.cc.utexas.edu> ethan@emx.cc.utexas.edu (Ethan T. Vishniac) writes:
>
>In cases like this the request for appropriate references
>is doomed to failure, but making the request makes a point
>so....
>
>How about CARP?  
>
>Cite Appropriate References Please

I'd suggest a slight modification: CRAP

	Cite References Appropriately Please

-Bill
-- 
Bill Tyler      wtyler@adobe.com
Newsgroups: sci.physics
From: blanton@mksol.dseg.ti.com (John F Blanton)
Subject: Re: satellite orbits
Organization: Texas Instruments, Inc
Date: Mon, 25 Jan 1993 23:09:52 GMT

Strictly speaking, you can't call the force the satellite
exerts on the earth "centrifugal", which means "fleeing from
the center."  The force is really toward the center of the
CG of the satellite-earth system.

blanton@lobby.ti.com
From: taylors@hubcap.clemson.edu (C. Taylor Sutherland III)
Newsgroups: sci.physics
Subject: Re: Airplanes fly upside-down, how?
Date: 27 Jan 93 21:55:54 GMT
Organization: Clemson University

myrberger@e.kth.se () writes:

>Hi,

>my question is simple this: How can an airplane fly upside-down?

>The normal explanation for how airplanes fly is (simplified perhaps):

>The wing is formed so the air have a longer way to go on the top, 
>therefore the air moves faster and an upward force is a fact.

>But when an airplane flies upside-down, a downward force should appear? Right?

Right, but then you increase the angle of attack (nose the plane over from
the pilots perspective) and you then have a longer path for hte air to follow
on top of the wing than on the bottom (you also have a kite effect) and 
POOF...Lift.


-- 
	     We're not hitchhiking anymore.  We're riding!
		     -The Immor(t)al Ren & Stimpy-
         The Fly Boy  <| E-MAIL:  taylors@hubcap.clemson.edu |>
+--<| My life is a math question with one equation and 42 unknowns. |>--+
Newsgroups: sci.physics,sci.skeptic,alt.paranormal,alt.sci.physics.new-theories,rec.arts.startrek.tech
From: nelson_p@apollo.hp.com (Peter Nelson)
Subject: Re: New Physics, Healing, Paranormal
Date: Wed, 27 Jan 1993 20:17:52 GMT
Organization: Hewlett-Packard Corporation, Chelmsford, MA

In article <C1IyHB.9qK@dcs.ed.ac.uk> pdc@dcs.ed.ac.uk (Paul Crowley) writes:
>Quoting sarfatti@well.sf.ca.us (Jack Sarfatti) in article <C1GEpL.4H7@well.sf.ca.us>:
>>
>>This is no joke! I have been told that I am a "super star" in some powerful
>>circles that have decided that traditional universities are "brain dead"
>>and that something new-age is needed.
>
>Might be true in powerful circles.  Here, sweetie, you're just another
>poster.

   I know spelling flames are frowned upon but where I'm from 
   his posting sounds more like it's from an IMposter.


---peter
From: hall@vice.ICO.TEK.COM (Hal F Lillywhite)
Newsgroups: sci.physics
Subject: Re: Airplanes fly upside-down, how?
Date: 28 Jan 93 15:39:36 GMT
Organization: Tektronix Inc., Beaverton, Or.

In article <1993Jan28.055248.9009@sfu.ca> palmer@sfu.ca (Leigh Palmer) writes:

>                                                       Airplanes fly by
>climbing up on a virtual pillow of increased air pressure which supports
>the
>entire weight of the aircraft. That this is so is well known to pilots who
>have experienced the greater ease with which this is done by a plane
>flying
>near the ground. It is the reason waterfowl cover great distances
>scarcely 
>a wingspan above the surface; it's much easier to fly there, and its much
>easier to see that they are constantly climbing onto that "pillow". 

Uh, Leigh I think you blew it with the waterfowl example.  "Great
distances" is rather undefined but when waterfowl want to fly really
long distances (as in migration) they use an altitude much greater
than a wingspan above the surface.  Yes they will fly a ways near
the surface, maybe from nest to food etc.   However for the fall 
flight south and spring return north (Northern Hemisphere) they fly 
hundreds or even thousands of feet above the surface.

What you have described is the "ground effect."  Near the surface a
flying object will compress air between itself and the ground (or
water) providing more lift.  Among humans the experts on this would
include helicopter pilots who notice it when making slow landings
and especially no power emergency landings.  (The effect is less
noticible with the higher speed landings of fixed wing aircraft.)
However this extra lift comes with a penalty, namely that the thicker
air provides more resistance to forward motion.  Higher altitude
flight avoids this and is more efficient for long distance travel.
I speculate that this is the reason that a waterfowl will fly low
when carrying a load of food back to the young in the nest but high 
when migrating.  You will also notice that any long distance airline
flight climbs to an altitude of 20,000 ft. or above (usually well
above).  The purpose is to reach thinner air at those altitudes,
thus reducing air friction and saving fuel.
Newsgroups: sci.physics,alt.sci.physics.new-theories,sci.skeptic,alt.paranormal,alt.conspiracy,alt.pagan,alt.magick,alt.alien.visitors,rec.arts.startrek.tech
From: ppawels@eos.ncsu.edu (PAUL  PAWELSKI)
Subject: Re: New University - Call for Faculty and Students
Originator: ppawels@c00083-100lez.eos.ncsu.edu
Reply-To: ppawels@eos.ncsu.edu (PAUL  PAWELSKI)
Organization: North Carolina State University, Project Eos
Date: Wed, 27 Jan 1993 14:48:51 GMT


In article <C1I7Io.25z@well.sf.ca.us>, sarfatti@well.sf.ca.us (Jack Sarfatti) writes:
> VISIONARY PHYSICIST, DR. JACK SARFATTI, APPOINTED TO SCIENCE BOARD OF WORLD
> UNIVERSITY
> Start of Press release
> ACADEMIE  UNIVERSITAIRE  LIBRE  MONDIALE
> ----------------------------------------------------------------------
> WORLD  UNIVERSITY
>
{stuff out} 
> 
> A Scientific Board of top quality scholars coming from both the "Exact
> Sciences" and "Human and Social Sciences" is now being established by Dr.
> Paul A. Gerome of Geneva, Switzerland. Dr. Jerome received his Ph.D. under
> Levi-Straus.
> 
{stuff out}
> 
> The first official act will be an International Conference using multimedia
> and telepresence. The recording of the Conference will be broadcast by
> satellite. The Scientific Board members will define the new hybrid sciences
> and give them names.


The misnaming of fields of study is so common as to lead to what might
be general systems laws.  For example, Frank Harary once suggested the
law that any field that had the word "science" in its name was
guaranteed thereby not to be a science.  He would cite as examples
Military Science, Library Science, Political Science, Homemaking
Science, Social Science, and Computer Science.  Discuss the generality
of this law, and possible reasons for its predictive
power.
                -- Gerald Weinberg, "An Introduction to General Systems
                   Thinking."
----------------------------------------------------------------------

Colorful, Jack, be careful though, too many of us have too limited of a sense
of humor: excessive play on this thread may cause people to ignore your 
thoughts on other threads.

Paul Pawelski
Newsgroups: sci.physics,sci.skeptic,alt.paranormal,alt.sci.physics.new-theories,rec.arts.startrek.tech
From: eriks@lin.foa.se (Erik Svensson FOA2)
Subject: Re: New Physics, Healing, Paranormal
Organization: FOA, Linkoping, Sweden
Date: Tue, 26 Jan 1993 13:26:21 GMT

>sarfatti@well.sf.ca.us (Jack Sarfatti) writes:

>I am being paid a significant amount of money to write this by an
>influential European corporation. If you want to make
>corrections,suggestions etc. with no monetary compensation from me,feel free
>to do so. I will include opposing points of view in footnotes with your
>names if you like. All I can say is that this document is going to be
>translated into Spanish, French, Portuguese,Russian, Hindi and will be
>read by some of the most powerful people (politicians, CEO's of multi-
>nationals etc.) in the world who are about to set up a satellite based
>multi-media world wide university in which I have been asked to play a
>major role with major funding.

>This is no joke! I have been told that I am a "super star" in some powerful
>circles that have decided that traditional universities are "brain dead"
>and that something new-age is needed.

If somebody's paying you for this, the universities aren't the only thing 
that's brain dead.

(hope it won't be translated into swedish. Think of the forests saved)

cheers 
--
     Erik Svensson
    Research Officer            National Defense Research Establishment (FOA)
 Guided Weapons Division        Stockholm, Sweden      eriks@fenix.lin.foa.se

"The problem with the future is that it keeps turning into the present"
 -- Hobbes
From: ledwards@leland.Stanford.EDU (Laurence James Edwards)
Subject: Re: satellite orbits
Organization: DSG, Stanford University, CA 94305, USA
Date: Fri, 22 Jan 93 01:53:34 GMT

In article <1993Jan21.213632.3246@newshost.lanl.gov>, u108502@beta.lanl.gov (Andrew Poutiatine) writes:
|> In article <376oXB3w165w@netlink.cts.com> bigbro@netlink.cts.com (Kenneth Sullivan) writes:
|> >Quick easy question, this is mostly to settle an arguement
|> >
|> >a.)what keeps a satellite in orbit
|> >and 
|> >b.)just how wrong is the idea of centrifugal/centripidal "force"?
|> >thanks
|> >
|> [...]
|> If the satellite is moving too slowly initially to maintain a stable orbit, 
|> then it falls, speeding up, until a stable orbit is maintained, unless of 
|> course it enters the atmosphere or hits the ground or something.
|> 
|> The gravitational force is toward the Earth, and is hence a centripital force.
|> In this simple example there is no centrifugal force.
                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
If the earth exerts a centripetal force on the satellite I would think the
satellite exerts a centrifugal force on the earth, as you mention subsequently
with the example of the ball and string.

Larry Edwards
From: bob@1776.COM (Robert Coe)
Newsgroups: sci.physics
Subject: Re: Truth vs beauty in physical theories
Date: Sun, 24 Jan 93 20:24:56 EST
Distribution: world
Organization: 1776 Enterprises, Sudbury MA

barry@arnold.math.ucla.edu (Barry Merriman) writes:
> Obviously, we can only work with theories that are simple enough for us
> to understand, and that guarantees a certain level of simplicity, either
> in the theory or in its applications. 

I accept that, but....

> But these are all statements about _us_, not the universe. So I still
> see no reason to think the universe is simple. Rather, we'll only
> ever understand those parts of it that are.

For at least the last 300 years, the really major advances in our under-
standing of the universe have come not from the discovery of increased com-
plexity (important as such discoveries have been), but from the eventual 
realization that the complexity could be best understood in the context of
a more global, but ultimately simpler, synthesis.  That this keeps happening 
may not be a reason to think that the universe is simple.  But it is a reason 
to suspect that the complexity is not fundamental, but arises from the cumu-
lative effect of the application of simple - and discoverable - principles.

   ___            _                                           -  Bob
   /__) _   /    / ) _   _
(_/__) (_)_(_)  (___(_)_(/_______________________________________ bob@1776.COM
Robert K. Coe ** 14 Churchill St, Sudbury, Massachusetts 01776 ** 508-443-3265