HDTenEightyP/NetNews huggingface dataset:
From: metzler@pablo.physics.lsa.umich.edu (Chris Metzler)
Newsgroups: sci.physics
Subject: Re: two point masses in an expanding universe
Date: 12 Jan 1993 07:35:01 GMT
Organization: University of Michigan Department of Physics
Distribution: world
NNTP-Posting-Host: pablo.physics.lsa.umich.edu

In article <davidm.726275008@questor>, davidm@questor.Rational.COM (David Moore) writes:
|> sichase@csa1.lbl.gov (SCOTT I CHASE) writes:
|> 
|> 
|> >No.  At a given point in time in an expanding Universe, objects further
|> >apart move faster with respect to one another.  But over time, the
|> >relative velocity, due to the Hubble expansion, of two objects *decreases*
|> >due to the self-gravitation of the objects in the Universe slowing 
|> >the expansion.
|> 
|> Is there experimental evidence for this? For example, the density of
|> distant galaxies should be greater than nearby ones (as I believe has
|> been verified), and the change of density with distance should
|> reflect the gravitational attraction. (In other words d2D/dx2>0)
|> 

There is another type of experimental verification for the change in the
Hubble parameter that Scott explains later in his message.  It's not a
very strong verification, however.

The Hubble law that we all know and love, 

	c * z = H_o * r, where c is the speed of light
                               z is the redshift
                               H_o is the Hubble constant
                               r is the distance

is actually the low z limit of a more complicated expression known as
the redshift-distance relation (see Weinberg 1972, pp 441-442 for more).
If we do a series expansion of this relation, we see that the expression
for r involves terms not only of first order in z (the usual Hubble law),
but second order and higher terms.  The coefficient of the quadratic term
(which we expect to be the next term of importance as we go to higher z)
you can essentially think of as involving the time-derivative of the
Hubble "constant".  By measuring the redshift of distant objects, as well
as their distance (NOT by using the Hubble law, but by some independant
method), and then by curve-fitting, one can ostensibly find the coefficient,
thus the time-derivative of the Hubble constant.  This also provides a
method of getting at \Omega, because in a matter-dominated universe,

           \Omega = -2 * ( dH/dt + H^2) .

However, the sad truth is that it is very very difficult to get independant
distance estimates for galaxies at that high redshift.  The error bars are
huge -- so huge that it's not possible to discriminate between interesting
world models at this time.


-- 
SNAILMAIL:                                       AT&TMAIL:
Chris Metzler                                    313-764-4607 (office)
Department of Physics, University of Michigan    313-996-9249 (home)
Randall Lab, 500 E. University
Ann Arbor, MI  48109-1120 USA

E-MAIL:  metzler@pablo.physics.lsa.umich.edu
From: bhoughto@sedona.intel.com (Blair P. Houghton)
Newsgroups: sci.physics
Subject: Re: sci.physics.research: proposed panel of moderators
Date: 9 Jan 1993 21:48:47 GMT
Organization: Intel Corp., Chandler, Arizona
NNTP-Posting-Host: stealth.intel.com

In article <1993Jan9.182355.20379@murdoch.acc.Virginia.EDU> crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass) writes:
>In article <478@mtnmath.UUCP> paul@mtnmath.UUCP (Paul Budnik) writes:
>>In article <1993Jan9.002324.22505@galois.mit.edu>, jbaez@riesz.mit.edu (John C. Baez) writes:
>     'Not even wrong' is a succinct way of saying that the phrase
>     'muons decay because of their innate desire to be free' would
>     be unacceptable.  In my view, this would not necessarily apply
>     to postings about philosophy of QM.

Lovely.  Metaphor is rejected out of hand.  Schrodinger's cat
will be very disappointed to know that he's dead.

>     It is inappropriate to consider the name of the poster when
>     making moderation decisions, but if a posting reaches
>     the level of being clearly wrong, it should not be acceptable.

Lovely.  Refutable argumentation is rejected out of hand.
Sort of like we don't even need to discuss it if it's
going to be discussed...  this sort of infringes on
Joseph Heller's copyright, wot?

>     I'm not going to speak for John, but it seems to be the re-hashing
>     process that is the sticking point.  It should not be all that
>     difficult to determine when a thread is only plowing up a field
>     previously tilled with the same plow and to coax the participants
>     onto new ground.

Lovely.  Reasoning by group induction is rejected out of
hand.  Heaven help us if we need to make a refutable
assumption about a metaphorical situation in a
gedankenexperiment involving the contradiction of a
self-supporting conjecture.

>     Maybe we should be more positive in what we are talking about.
>     In my view, we should encourage vigourous and substantial discussion
>     in all areas of physics.

Viva Caloric!

				--Blair
				  "Methinks the candidates
				   doth protest too little."
Newsgroups: sci.physics
From: Leigh Palmer <palmer@sfu.ca>
Subject: Re: *.research request: limit number of articles per day
X-Xxmessage-Id: <A7745F99BE021C15@21.28.189.128.in-addr.arpa>
X-Xxdate: Sat, 9 Jan 93 18:55:21 GMT
Organization: Simon Fraser University
X-Useragent: Nuntius v1.1.1d16
Date: Sat, 9 Jan 1993 18:53:47 GMT

In article <1993Jan9.153636.12903@black.ox.ac.uk> David Rabson,
rabson@oxford.ac.uk writes:
>I should like to suggest that the moderated, research-oriented newsgroup
>should have a limit on the number of articles posted each day.  Twelve
seems
>like a good number; it can be raised later if the moderators deem it
>helpful.

I fully support the idea of a limited number of articles in a group 
with the purpose of promoting scholarly interchange. Twelve may be 
the correct number in Oxford, but I think that a more appropriate 
limit would be to the number of topics (threads) to which any author
could contribute in one day, and I think a more appropriate number
is smaller, two or three per day. I would expect the quality of the
contributions to increase significantly above its present level, and
I would also expect to spend less time weeding than I do now.

Leigh
Xref: sparky sci.physics:22446 news.groups:25298 sci.misc:1998
From: bhoughto@sedona.intel.com (Blair P. Houghton)
Newsgroups: sci.physics,news.groups,sci.misc
Subject: Re: sci.physics.research: proposed panel of moderators
Date: 10 Jan 1993 23:48:52 GMT
Organization: Intel Corp., Chandler, Arizona
NNTP-Posting-Host: stealth.intel.com

In article <1993Jan10.003901.11589@infodev.cam.ac.uk> gjm11@cus.cam.ac.uk (G.J. McCaughan) writes:
>In article <1ingd7INNctm@chnews.intel.com>, bhoughto@sedona.intel.com (Blair P. Houghton) writes:
>> Let's just say that this is the sort of intellectual
>> dishonesty that results in pronouncements that certain
>> regions of philosophy are off-limits to exploration of
>> a certain kind.
>
>Pardon me, but what on earth are you on about?

"Religion & Physics Don't Mix" ring a bell?

				--Blair
				  "I don't know his name,
				   but his face..."
From: abian@iastate.edu (Alexander Abian)
Subject: TIME HAS INERTIA     Att: Andrew Martin FRAMINGHAM
Summary: a
Keywords: a
Organization: Iowa State University, Ames IA
Date: Wed, 6 Jan 1993 04:59:39 GMT


Dear Mr. Framingham:

    Thank you for your very thoughtful e-mail.  I answer via
newsnet sci.physics TIME HAS INERTIA (because it makes me feel secure)

    I read carefully your e-mail.  
    I have no objection if  you consider "The Fulfillment of Destiny" 
is the basic principle behind every action"  and I would not try to dissuade 
you.  
    Some people (in fact many scientists and physicists) believe  that the 
motivating and moving force behind every action is  " A Supernatural, 
omnipotent guiding divine spirit".  I have no objection to that either.  
    
   Some people compare my (A3) to saying that "Things act the 
way they act because gaga is gaga" .  I have no objection to that
either.  I do not ridicule them or do not try to dissuade or exhort 
against them.

   To me, my (A3) is the most convincing, i.e.,

(A3)    The primal cause of action of everything (from a particle to a
        person to a planet  to a galaxy, animate or inanimate objects,
        etc.)  is
(A3)                GAINING A FEELING OF SECURITY
          

   In fact the reason that people tell me that (A3) is the same as
"gaga is gaga" because that gives them a feeling of security, that 
makes them feel secure.

  I do not have to prove or to persuade people of the righteousness
of my (A3).  They will  themselves realize the rightfulness, the
rectitude of my (A3).  Every cell in our organism trembles with
fear of annihilation and acts to gain a feeling of security.

 Churchill, Stalin, Mother Theresa of Calcutta,  Genghiz Khan and
 Tamerlane, and every electron, proton, every particle acts in  
such a way as to FEEL MORE SECURE.  There is no better explanation, 
no better reason, no more convincing explication for the cause of 
every action than

(A3)    GAINING A FEELING OF SECURITY

  The sooner Physics accepts (A3) the sooner Physics will reflect the
reality.
  
  If you disagree with me  that  makes you feel secure, if you agree
with me that also makes you feel secure.  This circumstance BY NO
MEANS DEGRADES OR DISCREDITS MY (A3).  IT CONVINCES ME AND IT MAKES
ME FEEL SECURE THAT I CAME UPON  (A3)

  With best regards. Thank you.       Alexander Abian






-- 
   The tendency of maintaining the status-quo, Reaction to provocation and
                The tendency of maintaining again a status-quo.  
    TIME HAS INERTIA  and some energy is lost to move Time forward  
  E = mcc  (Einstein)    must be replaced by    E = m(0) exp(-At) (Abian)
Organization: Penn State University
Date: Thu, 7 Jan 1993 14:44:02 EST
From: <CCB104@psuvm.psu.edu>
Newsgroups: sci.physics
Subject: Gen. Rel. Using SI Units

Is there a good book or paper in which various constants of proportionality
as well as electromagnetic quantities (such as 4-dim. electromagnetic vector
potential and electromagnetic "matter tensors) are either shown explicitly
(instead of having c = ... = 1) or, especially in the case of the electro-
magnetic quantities, written in SI units, so that, for example, the
Reissner-Nordstroem solution electric-charge-term in the metric appears
with SI units of charge, distance, etc.?

Even if trying to figure it all out on one's own, it would be nice to have
something to check against.

Thanks!

Carey

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
                  "Squirrels are people too."
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Newsgroups: sci.physics
From: bhv@areaplg2.corp.mot.com (Bronis Vidugiris)
Subject: Re: A proof that quantum mechanics is an incomplete theory
Organization: Motorola, CCR&D, CORP, Schaumburg, IL
Date: Thu, 7 Jan 1993 17:51:00 GMT

In article <470@mtnmath.UUCP> paul@mtnmath.UUCP (Paul Budnik) writes:
)I do not understand how this argument applys to the case I presented.
)Maxwell's equations are a local theory. You cannot get a violation of
)Bell's inequality using them. If Maxwell's equation's could be used
)to predict a delay it could not be any *shorter* then the time it takes
)for light to travel from either polarizer to the more distant detector
)and this would be in contradiction with quantum mechanics.
)Of course there is nothing like a pair of singlet state photons in Maxwell's
)theory and that theory cannot applied to the problem of testing Bell's
)inequality.
)
)Paul Budnik

My point, such as it was, was that I would expect simple-minded classical
predictions to also hold true for QM, because in the limit for large number
of particles QM results in classical predictions.  Especially for something
simple-minded like a delay.  I just don't think that we are going to see
anything other than the simple t = d/c sort of delay come out of any
experiment.  The major place Maxwell's equations come into this simple
formula is in any  necessary adjustment of 'c' from the free-space value,
BTW.

In spite of the fact that QM requires one to do odd things like sum intergals
over all possible paths (at least using the Feynman approach) the results
ultimately match the classical ones as far as delays go, (at least if the
paths are of macroscopic length) - even though the method of arriving at the
result is a lot different.

As far as classical equivalents to the Aspect experiment go, I'm not as
sure as you are that something roughly analogous couldn't be thought up with
a pair of polarized beams randomly (but identically) phase modulated, but I
haven't really thought this through.
From: mcirvin@husc8.harvard.edu (Matt McIrvin)
Newsgroups: sci.physics
Subject: Re: Unit of space-time.
Date: 8 Jan 93 18:40:50 GMT
Article-I.D.: husc.mcirvin.726518450

pete_leaback@cix.compulink.co.uk (Peter Leaback) writes:

>From my singularly unmathematical book on relativity (Bertrand Russell's
>"ABC of Relativity"), I can't make up my mind as to what the unit of an 
>interval is.

It can be either a space unit like the meter or a time unit like the
second, depending on how you want to define it.  If you want intervals
to be measured in space units, then the proper definition will be
something like

l^2 = (ct)^2 - x^2 - y^2 - z^2

(with a possible overall minus sign, also according to taste).

If you want to measure intervals in time units, it's

l^2 = t^2 - (x/c)^2 - (y/c)^2 - (z/c)^2.

The factors of c take care of the units.  Now people who deal with
relativity on a daily basis usually take c = 1 and measure time and
space in the same units; with this point of view one second is the
same thing as 3x10^8 meters.  Then the factors of c drop out of the
formulae.
  
-- 
Matt McIrvin         I read Usenet just for the	tab damage!
==== =======         = ==== ====== ==== === === === =======
From: strobel@stein.u.washington.edu (Nicolas Strobel)
Newsgroups: sci.physics
Subject: collision times in differentially rotating disk
Summary: derivation of collision rates in galactic disk wanted
Keywords: galaxy disk collisions
Date: 12 Jan 93 21:14:30 GMT
Article-I.D.: shelley.1ivcbmINNs9t
Organization: University of Washington
NNTP-Posting-Host: stein.u.washington.edu


Can anyone give me a derivation of the timescale between collisions of
objects in the slightly less trivial case of a rotating galactic disk?
I know the timescales for a spherically distributed system with no net
rotation. The case of a flattened system whose rotation tends to keep
objects from colliding as frequently as if there was no rotation should
be a little trickier to find. The particular case I'm interested in is
one for a flat rotation curve galactic disk with a given velocity 
dispersion ellipsoid (or epicyclic frequencies).

Please email. If there is interest, I'll post what answers I receive.

Thanks
Nick Strobel
strobel@dirac.phys.washington.edu
From: Richard.Mathews@West.Sun.COM (Richard M. Mathews)
Newsgroups: sci.physics
Subject: Re: Faster then the speed of light?
Date: 8 Jan 93 01:11:30 GMT
Organization: Sunsoft Inc., Los Angeles, CA.
NNTP-Posting-Host: astro
Originator: richard@astro

matt@physics2.berkeley.edu (Matt Austern) writes:

>Depending on exactly how you define your terms, there is nothing wrong
>with the relative velocity of two objects being greater than c.

>Definition 1: the relative velocity of object 1 and object 2 is defined
>	to be the velocity of object 2 in the rest frame of object 1.

>Definition 2: the relative velocity of object 1 and object 2 is defined
>	to be the velocity of object 2 with respect to the observer,
>	minus the velocity of object 1 with respect to the same
>	observer.


All this is true, but it has nothing to do with what this speaker was
most certainly discussing.  The problem is with the use of triangulation
to deduce the tangential speed.

If an object is moving almost directly towards you at almost the speed
of light and if you observe it on two occasions, the light received on
the second occasion will have been traveling for much less time (in
your frame) than the light received earlier.  If you calculate the
transverse velocity by dividing the transverse distance by the time
between observations, you will get an absurd answer.  To get the correct
transverse velocity, you must use the time between when the two bits of
light were emitted, not the time between the two observations.  Using the
incorrect triangulation method, it is possible to get an arbitrarily large
"transverse velocity" result.  SR is not violated -- this is predicted by
SR.

     Richard M. Mathews			Lietuva laisva = Free Lithuania
					Brivu Latviju  = Free Latvia
Richard.Mathews@West.Sun.COM		Eesti vabaks   = Free Estonia
					        WE  DID  IT!!!
Newsgroups: sci.physics
From: crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass)
Subject: Re: sci.physics.research: Are there important unresolved issues?
Organization: University of Virginia
Date: Tue, 12 Jan 1993 23:50:18 GMT

In article <MERRITT.93Jan12180017@macro.bu.edu> merritt@macro.bu.edu (Sean Merritt) writes:
>In article <1993Jan12.203251.18849@murdoch.acc.Virginia.EDU> crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass) writes:
>
>#	First, if a 'channel' becomes noisy, then someone is not 
>#	doing their job properly, and I hope someone would point that out.
>
>Since there is no definitive defintion this(the "job") is left to the reader.
>
>"One man's noise is another's signal"

     The whole point of the group is to *not* leave the 'job' to the 
     reader.  I don't know about you, but collectively we have generated
     nearly half a meg (including thousands of prospective moderator's words)
     delineating the 'job' as we now see it.  I had nearly
     a thousand lines of correspondence with you personally (just before 
     Matt posted the charter) in an attempt to assuage fears and present
     a coherent philosophy.  If it is not at least generally understood 
     by now, I know no way to do so.

     As far as the quotation goes, I hope all the moderators agree
     on what constitutes noise and what constitutes signal.  As far as
     humanly possible, I think we do.

                           dale bass
-- 
C. R. Bass                                          crb7q@virginia.edu        
Department of Mechanical, 
     Aerospace and Nuclear Engineering
University of Virginia                              (804) 924-7926
From: jeffv@physics.ubc.ca (Jeff Vavasour)
Newsgroups: sci.physics
Subject: Need suggestions for numerical diffusion problem
Date: 13 Jan 1993 00:15:53 GMT
Organization: The University of British Columbia
Distribution: world
NNTP-Posting-Host: physics.ubc.ca

Hi, I've been working on a problem that involves diffusion in a potential
V(x,y,z) that has the symmetry of a diamond lattice.  My probability 
P(x,y,z,t) is given by

  __2
K \/ P - V P = dP/dt

which I would like to solve numerically for some smooth V with its values 
known only on some grid.

This problem easily reduces to a one-dimensional problem in cylindrical or
spherical symmetries, but I've been having some difficulty in the discrete
symmetry of the diamond lattice.  A general 3-D solution with appropriate
boundary conditions would work, but a 100 interval 1-D numerical solution in
the cylindrical or spherical case becomes a 100x100x100 3-D solution in the
diamond symmetry requiring much too much computation time.  There are also 
some problems with stability (not of the PDE solution, but of the 
self-consistent field that it is a part of).

Does anyone know of any references that might provide clue for simplification?
I would expect that there's probably some work out there where Schroedinger's
equation was solved in this symmetry which have an adoptable method, but I
haven't been successful in finding one.  (Perhaps a Hartree-Fock treatment of
the electron distribution in a diamond lattice?)

Please e-mail me.  Any help would be appreciated.

- Jeff


Newsgroups: sci.physics
From: pratt@Sunburn.Stanford.EDU (Vaughan R. Pratt)
Subject: Re: TIME HAS INERTIA   - STRICTLY FOR DEVOTED READERS OF: TIME HAS INERTIA
Keywords: Attention Mr. ELI HAWKINS
Organization: Computer Science Department,  Stanford University.
Date: Fri, 8 Jan 1993 06:38:20 GMT

In article <abian.726458073@pv343f.vincent.iastate.edu> abian@iastate.edu (Alexander Abian) writes:
>
>The ordinary language is the best tool which develops, sharpens and 
>polishes the human intellect.  The ordinary language is the REAL MIRACLE 
>OF CREATION. IT IS THE MECHANISM OF RATIONALITY. IT IS THE MECHANISM OF 
>REASONING.  THE ORDINARY LANGUAGE IS THE LIFE OF THE LIFE.    
>  
>Mathematical language is a most emotional, romantic and sensuous
>language.  
>

Language is dandy but menus are quicker.
-- 
Vaughan Pratt				There's safety in certain numbers.
Newsgroups: sci.physics,news.groups,sci.misc
From: jac@ds8.scri.fsu.edu (Jim Carr)
Newsgroups: sci.physics
Subject: Re: TOP in TIME
Date: 12 Jan 93 18:37:06 GMT
Reply-To: jac@ds8.scri.fsu.edu (Jim Carr)
Organization: SCRI, Florida State University

In article <MATT.93Jan11102448@physics2.berkeley.edu> matt@physics.berkeley.edu writes:
>
>ask this question: if the top has a mass of 130 or 140 GeV, then what
>is the expected number of events that would be seen with the
>integrated luminosity that they have at Fermilab?
>
>The answer is: considerably less than one.  The t-tbar cross section

Is that for CDF or D0?  They have quite different efficiencies, so 
seeing one event at D0 for a given luminosity would correspond to 
a higher top mass, would it not? 

I think the real reason that they (D0) are not prepared to say much about 
consequences (even off the record) has to do with the fact that the 
detector efficiencies are a function of the event energy and topology, 
so the relation of the observed event to an overall t-tbar production 
rate is not known very well at this time (for D0 at least).  

--
J. A. Carr                                    |  "The New Frontier of which I  
jac@gw.scri.fsu.edu                           |  speak is not a set of promises
Florida State University  B-186               |  -- it is a set of challenges."
Supercomputer Computations Research Institute |   John F. Kennedy (15 July 60)
Newsgroups: sci.physics,alt.sci.physics.new-theories