HDTenEightyP/NetNews huggingface dataset:
From: johan@blade.stack.urc.tue.nl (Johan Wevers)
Newsgroups: sci.physics
Subject: Re: Mass renormalization.
Date: 14 Sep 92 13:59:01 GMT

jbaez@riesz.mit.edu (John C. Baez) writes:

>>m(r)=m_0 + e^2/r - Gm^2(r)/r

>>Because in the third term on the right-hand side we have m(r) instead
>>of m_0 , we receive in the limit r->0: m(r)= e/\sqrt{G}. Finite.

>Typical renormalization theory arguments ignore general relativity (and
>indeed, gravity altogether)

Maybe the equation above is an indication that quantum gravity will solve
the problem of renormalization. (though all QG theories offered yet are
not renormalizable........).

>Folks, it's not quantitized, or quantisized, it's just quantized.

Sorry, my physics skills are much beter than my language skills. And I'm
not a native speaker (as you all might have observed from my postings and
my email adress).

******************************************************************** 
* J.C.A. Wevers                *         u\  _\       /e+        2 * 
* johan@blade.stack.urc.tue.nl *     1 |   \ u \  X  /         |   * 
******************************** P = - |    >   >---<     + ...|   * 
*     The only nature of       *     N |   /   /     \         |   * 
*     reality is physics       *         u/   /d     u\            *
********************************************************************
From: toon@moene.indiv.nluug.nl (Toon Moene)
Newsgroups: sci.physics
Subject: Are the basic laws of physics simple or beyond comprehension ?
Date: 9 Sep 92 19:31:25 GMT
Organization: Moene Computational Physics, Amsterdam, The Netherlands

In article <1992Sep8.182555.2789@galois.mit.edu> jbaez@riesz.mit.edu (John  
C. Baez) writes:
> In article <1992Sep8.023027.15883@nuscc.nus.sg> matmcinn@nuscc.nus.sg  
(Mcinnes B T (Dr)) writes:

[ ... B T Mcinnes:  String theory seems to be hard to grasp
      John C. Baez: So were Newtons laws in the 18'th century ... ]

> >Would one not expect a priori that
> >the universe should be either easily comprehensible to all, or vastly
> >beyond the intellect of even a Fields medallist?  :)
> 
> It's probably both.  I imagine that the basic laws are very simple but
> deducing all their consequences is essentially impossible.

There's a nice story by the late Isaac Asimov on just this issue:  
Nightfall. It was quite famous in its time (early 1940's). It is about a  
bunch of astronomers deducing a world catastrophe because of an eclipse on  
a planet in an orbit 'around' six suns.

This quote does it for me:

'And I've got another cute little notion,' Beenay said. 'Have you ever  
thought wat a simple problem gravitation would be if only you had a  
sufficiently simple system ? Supposing you had a universe in which there  
was a planet and only one sun. The planet would travel in a perfect  
ellipse and the exact nature of the gravitational force would be so  
evident it could be accepted as an axiom. [ ... ]'

--
Toon Moene (toon@moene.indiv.nluug.nl)
Kantershof 269, 1104 GN  Amsterdam, The Netherlands
Tel.: + 31 20 6982029; Fax: + 31 20 6003411
No Disclaimers; a NeXT at home protects against this occupational hazard.
From: Rick.Ellis@ofa123.fidonet.org
Newsgroups: sci.physics
Subject: Re: AT WHAT HEIGHT IS GRAVITY PERCEPTIBLE?
X-Sender: newtout 0.02 Aug 21 1992
Date: 15 Sep 92  13:45:28

On <Sep 15 13:45> Joe Voros writes:

 JV> Well, astronauts on the Moon don't feel any gravity, 'cos they're so far
 JV> away from the Earth.  The only reason they don't float away is because
 JV> they wear Heavy Boots.

 JV> :)  (for the humour-impaired)

Didn't Danny Quayle say that?
From: weemba@sagi.wistar.upenn.edu (Matthew P Wiener)
Newsgroups: sci.physics
Subject: Re: Computability of the universe
Date: 13 Sep 92 21:01:35 GMT
Reply-To: weemba@sagi.wistar.upenn.edu (Matthew P Wiener)
Organization: The Wistar Institute of Anatomy and Biology
In-reply-to: jbaez@riesz.mit.edu (John C. Baez)

In article <1992Sep11.222036.7483@galois.mit.edu>, jbaez@riesz (John C. Baez) writes:
>Recursivity in quantum mechanics
>Transactions of the American Mathematical Society
>Vol. 280, 1983 p. 339.

>In short, the issue of computability for wave equations depends
>crucially on the precise space of solutions one works with, and a
>physically more realistic space of solutions gets rid of Pour-El and
>Richard's result.  So I am quite sure their effect cannot be used to
>build a device.

John is right that his paper prevents final conclusions about C-T from
being drawn from Pour-El & Richards' work.  However, I don't think your
paper is much in favor of C-T either.  For example, your argument does
not generalize in an obvious way into outside influences.  Presumably a
recursive environment + events situation could split non-recursively,
analogous to Gell-Mann & Hartle decoherence.  Penrose fans would argue
that no doubt mental infinity is modeled via wave function spectra,
which could easily include non-recursive spectra.

Curiously, Penrose, in the course of his grand overunified theory of
everything including the kitchen sink, did not refer to Geroch's idea,
that quantum gravity is likely to be non-recursive, on the grounds that
summing path integrals over 4-manifolds when you cannot even solve the
identity problem for 4-manifolds, will, in general, not be possible.
Whether *that* could lead to explicit violation of C-T is another
question.  (First, though, the question of how to verify inherently
non-recursive theories, while not insurmountable, has to be overcome!)
-- 
-Matthew P Wiener (weemba@sagi.wistar.upenn.edu)
Newsgroups: sci.physics
From: cannon@scs.unt.edu (Dustin Cannon (Lab 3460))
Subject: Quantitized Length
Organization: School of Community Service, UNT
Date: Mon, 7 Sep 1992 01:33:55 GMT

	I have a question.  I was thinking about the problem of the man 
walking across a bridge, but he first walks half the distance and then can 
only walk half the remaining distance and so on.  He never gets to the end, 
right? 
	Well, I was thinking that if length was quantitized just like 
charge.  Then the man would get to a point were he simply could no longer 
walk half the distance because he would be halving a quanta of length.
	I liked this because it also solves a rather disturbing idea one of 
my professors once said, which was that as two point charges come in contact 
with each other they have infinte potential energy due to 1/r.  This, he 
said, was in his mind a proof of God's exsistence.
	I have asked several of my professors about quantitized length, but 
they seem to dodge the question.  One however did tell me that quantum 
mechanics is couched in the idea of a countinous space-time and that this 
seems to be a good approximation, so why make the problem harder by throwing 
in quantitization of length.  I can understand this, but I would still like 
to know the truth.
	I would greatly appreciate anything anybody can tell me on this 
subject.  I have yet to take Quantum Mechanics so I'm deep in terra 
incognito.  Thanks ahead of time.
_________________________________________________________________
Dustin W. Cannon      "Just because some of us can read and write
University of          and do a little math, that doesn't mean we
North Texas            deserve to conquer the universe."
                                                -Kurt Vonnegut
From: merlin@neuro.usc.edu (merlin)
Newsgroups: sci.physics
Subject: Li6D and U238 cross section data
Date: 13 Sep 1992 02:09:04 -0700
Organization: University of Southern California, Los Angeles, CA
NNTP-Posting-Host: neuro.usc.edu

It's been too many years since I last looked at this data -- but I've
managed to get into an arguement with a friend about my thermonuclear
device design.  Basically, it's a fission device set next to a hollow
3.5 inch thick U-238 ellipsoid filled with Lithium-6 Deuteride.  His
claim is over half of the neutrons from a fission primary device will
not reach the second U-238 wall of the ellipsoid and as a consequence
the Li6D (or +n ==> T-D) will squirt out the far side of the device.
This is not what I recall from my early numerical model of the device
-- but it's been years -- and I don't have time to go back & dig out
the old cross section data & codes.  Let's assume something like 1MeV
neutrons are emitted from the primary fission device -- I don't even
remeber whether this is correct -- but I do recall the primary fission
neutrons were much softer than the 14.5 MeV neutrons from the fusion
secondary device.  The U-238 ellipsoid is roughly 18" outer diameter
and perhaps 16' overall length.  We could assume a 16' sphere is this
would simplify matters for answering this question.

Thanks, AJ

------------------------------------------------------------------------------
Alexander-James Annala
Principal Investigator
Neuroscience Image Analysis Network
HEDCO Neuroscience Building, Fifth Floor
University of Southern California
University Park
Los Angeles, CA 90089-2520
------------------------------------------------------------------------------

Newsgroups: sci.physics
From: serge@ramsey.cs.laurentian.ca (Serge Turgeon)
Subject: Finding published papers for an author
Organization: Dept. of Computer Science, Laurentian University, Sudbury, ON
Date: Tue, 15 Sep 1992 19:28:06 GMT

I'm trying to find some papers published by a few authors.  All I have is their last names and the names of a few journals they most likely published in.
(one of which is Physical Review A... and i don't enjoy the idea of looking through the index's for the last 5 years.)

Is there a system somewhere i can access to get a complete list of publication for an author?

Help would be really appreciated.

reply to serge@ramsey.cs.laurentian.ca

Newsgroups: sci.physics,sci.math
From: pratt@Sunburn.Stanford.EDU (Vaughan R. Pratt)
Subject: Re: Report on Philosophies of Physicists
Organization: Computer Science Department,  Stanford University.
Date: Sun, 13 Sep 1992 19:14:55 GMT

In article <TORKEL.92Sep13174850@bast.sics.se> torkel@sics.se (Torkel Franzen) writes:

>  Now, my claim is that the acceptance among mathematicians of set
>theory was (on the whole) due to its mathematical usefulness, not to their
>perceiving it as a means of interpreting and justifying existing
>mathematics.
>
>  In view of your current emphasis on terminology, it's not clear to what
>extent you disagree with this.

Can we split mathematicians into the chiefs and the indians, or since
that's politically incorrect these days, the officers and the troops?
The officers are focused on the central problems of mathematics *and*
at least some of their applications, even when they seem to be off
doing hopelessly pure mathematics.  The troops carry on, enjoying
themselves, instructing others, but generally paying close attention to
the direction the officers seem to be going in and not straying too far
away from them.  Granted this is a caricature, maybe even an offensive
one to some, but it serves the following purpose.

If so, then I think we can resolve our difference by saying that you
were talking about individual miscellaneous users of set theory, while
I had in mind the mathematicians one reads about in Dauben's book, who
for the most part sounded like officers who cared deeply about the
foundational role of set theory, whether in addition to or as part of
its mathematical use.

What I said in effect was that the army was attacking a strategic
target.  You contradicted this by observing that the troops were
blowing up bridges, digging trenches, etc.  I've already given some
evidence for the former, and I'm sure you're right about the latter
(though I should point out that you haven't responded to my request for
actual names after I responded to yours---perhaps forgiveable since
it's the officers who get remembered).

Foundations does have its own troops these days, but not I think prior
to the turn of the century.  (I'm not sure in what category to put
Zermelo, was he an officer in 1904 or just an NCO?)

One might ask, if the mathematical community is an army, who or what
are they fighting (besides congress)?

I view mathematics as war against inefficient thought.  Not against
ignorance, ignorance is not the real enemy.  Knowledge is only what we
think it to be, it has only relative permanence (1+1=2 will probably be
around longer than CH), and it is loyal to neither side: it can both
help and hinder efficient thought.  The best mathematics is that which
helps us all think more clearly.

-- 
======================================================| God found the positive
Vaughan Pratt   pratt@cs.Stanford.EDU   415-494-2545  | integers, zero was
======================================================| there when He arrived.
From: DOCTORJ@SLACVM.SLAC.STANFORD.EDU (Jon J Thaler)
Newsgroups: sci.physics
Subject: Re: Size of neutrino
Date: 15 Sep 92 16:52:26 GMT
Organization: Stanford Linear Accelerator Center

pratt@Sunburn.Stanford.EDU (Vaughan R. Pratt) says:

> mfm0@midway.uchicago.edu writes:
>> I seem to remember a upper bound on the size of an electron,
>> a statement like "we know that an electron is smaller than
>> 10^-x cm in diameter.

x is about 16.

> Then you have the corresponding lower bound on its momentum.  There is
> no a priori reason I know of to place any lower bound on the momentum
> of an electron.

This is incorrect.  A particle's motion does not depend in any direct way
on its size.  The "size" of an electron is determined from the form of
its interactions.  The concept is nearly identical to that which
Rutherford used to show that atoms have a small nucleus.
From: Richard.Mathews@West.Sun.COM (Richard M. Mathews)
Newsgroups: sci.physics
Subject: Re: Measuring the Universe
Date: 16 Sep 1992 01:32:15 GMT
Organization: Sunsoft Inc., Los Angeles, CA.
Distribution: sci
NNTP-Posting-Host: astro
Originator: richard@astro.West.Sun.COM

hagerman@ece.cmu.edu (John Hagerman) writes:
>When someone says "The universe if 20 billion years old," how is that
>measure affected by relativity?  Is it unambiguous?

It is unambiguous.  The claim is that the maximum proper time of any
path from the Big Bang to here and now is 20e9 years.

>On a related topic, I'll ask a FAQ not in the FAQ.  What would be the
>radius of a black hole containing the mass of the universe?  Current
>cosmological thought surely considers times when the universe was
>smaller than this; what are the implications?  Specifically, how can
>we say anything about the physics of the universe at such times, if we
>are reluctant to say anything about physics inside a black hole?

The normal black hole formula assumes an asymptotically flat space time
far from the hole -- it assumes that the hole has mass here, and space
is empty everywhere else.  Since the universe has mass distributed
uniformly, the black hole description just doesn't fit.  The universe
can have an arbitrarily large (including infinite) mass and still not
fit the definition of a black hole.

     Richard M. Mathews			D efend
					 E stonian-Latvian-Lithuanian
Richard.Mathews@West.Sun.COM		  I ndependence
Newsgroups: sci.physics
From: bhoughto@sedona.intel.com (Blair P. Houghton)
Subject: Re: How do we know individual photons exist?
Organization: Intel Corp., Chandler, Arizona
Date: Tue, 15 Sep 1992 18:50:56 GMT

In article <1992Sep15.180630.913@prim> prim!dave@germany.eu.net (Dave Griffiths) writes:
>When an electron has collected
>1000 sub-photons, it's state changes.

When an electron collects even one "sub-photon," its state changes;
perhaps not in the same way as when it collects a "whole" photon,
but it's certainly not the same as before.

				--Blair
				  "It's sort of like potato chips..."
From: mcirvin@husc8.harvard.edu (Mcirvin)
Newsgroups: sci.physics
Subject: Re: Question of Theory of Everything (or Grand Unified theory)
Date: 7 Sep 92 03:35:04 GMT

abbasi@star.enet.dec.com (My name is Nasser Abbasi) writes:

> read somewhere that a Theory of Everything, or the Grand Unified theory,
> or whatever you want to call it (that will unify the four forces of nature
> in one theory), will be found soon, may be in the next 10-20 years ?!

IMHO, people claiming this are a bit overenthusiastic.  Trying to
unify all the forces before a decent quantum theory of gravity even
exists is putting the cart before the horse.

> my question , will this theory be based on ?
> ie. SuperStrings? relativistic quantum mechanics or what?

Whatever it is, if and when it arrives, it will almost undoubtedly
incorporate relativistic quantum mechanics somehow, if only because all the
approaches being considered today (including superstrings) are varieties
of relativistic quantum mechanics.
 
-- 
Matt McIrvin, Cambridge, Massachusetts, USA 
Newsgroups: sci.physics,rec.pets.cats
From: frank@rover.uchicago.edu (Frank - Hardware Hacker - Borger)
Subject: Re: Radioactive Cat: How Dangerous is She?
News-Software: VAX/VMS VNEWS 1.41    
Reply-To: frank@rover.uchicago.edu
Organization: Joint Center for Radiation Therapy
Distribution: na
Date: Tue, 8 Sep 1992 23:56:00 GMT

In article <26160@dog.ee.lbl.gov>, sichase@csa2.lbl.gov writes...
>In article <t#rnaf+.hank@netcom.com>, hank@netcom.com (Hank Roberts) writes...
>> 
>>While I don't call it radiophobia, I'm certainly overcautious about
>>any risk when the question is one's own young children.
> 
>My concern is that radiation is not identifiable in the environment.  What
>if the veternary intern gave your cat too high a dose?  Before you knew
>what was going on, you would have accidentally overexposed your family.

	Radio-isotopes of this type have to be individually ordered, (since
	you not only have to specify amount of radiation, but state a time
	too, since halflife is on the order of 1/2 day.) To create any real
	hazard to your family, a mistake on the order of 100 to 1000 times
	would have to be made. At this level, by the time you went to pick
	up the cat... well you get the3 picture.


>Most other hazards in the home are more easily evaluated by the average
>adult.  I think I might bother to get a Geiger counter to judge for myself
>whether the cat was a radiation hazard to my family.  

	I have an old radioactive dial watch that I can use to Pin a geiger
	counter on it's most sensitive scale. I would wear it on my wrist
	without hesitation. Geiger counters are VERY sensitive detectors.
	(As an aside, if I invert the watch, and put the back instead of the
	glass dial against the tube, nothing happens.)

	Conversely, the wrong kind of counter might NOT pick up alphas,
	low level betas, etc. For example, they are useless for detecting
	Radon in the home.

	What I would do is: A/ Trust my vet,

			    B/ Ask him to explain what procedures they do to
			       assure proper dose, safety, etc.


	Remember, you can get killed driving to drop off the cat or pick it
	up too. All life is a bitch.

	Before anyone flames the last statement:

	1/ I once got tail-ended in an auto accident while dropping my dog off 
	   at the vet.

	2/ I was driving a 1971 PINTO...

	3/ My car had virtually no damage, the Oldsmobile that hit me had about
	   $1000, (1971 dollars,) of damage.

   Frank R. Borger - Physicist    __       Internet:  Frank@rover.uchicago.edu
Michael Reese - Univ. of Chicago |___      Phone : 312-791-8075 fax : 567-7455
  Center for Radiation Therapy   | |_) _   
                                   | \|_)  Dear son, don't come home and all is
    "Birthplace of Softball"          |_)  forgiven. - Personal ad.
Newsgroups: sci.physics
From: palmer@sfu.ca (Leigh Palmer)
Subject: Re: And another thing (was Re: QUESTION: General Relativity)
Organization: Simon Fraser University
Date: Sat, 12 Sep 1992 00:36:59 GMT

In article <11SEP199213115299@utahep.uta.edu> sawyer@utahep.uta.edu (Lee
Sawyer) writes:

>  I think I know the answer, but I would like to see the consensus
>of the group before I venture my guess... 

First let me say that this diatribe is not directed at Lee Sawyer. I'm flaming
a commonly held attitude which just bugs the Hell out of me. It's Friday, and
I'll feel better over the weekend if I relieve the pressure now. No offense
intended, Mr. Sawyer; you have just been honest enough to make this common
error explicitly.

I object to the philosophical orientation behind this statement, coming as it
does from someone who is probably either a scientist or who is at least trained
in science. What possible difference can it make what the "consensus" of a
group of either scientists or Yahoos is? The question is a scientific one. It
has an answer which is entirely insensitive to the consensus of any group. In
this case the answer is probably simple (the orthodox answer *is* simple, but
orthodoxy is just currently accepted prejudice, subject to revision whenever
experiment requires it).

It reminds me of a radio phone-in poll which was intended to decide the
question of whether Bill Cinton gets extramarital jollies or not. There is a
perfectly definite answer to the question, of course, whether one knows it or
not. I certainly don't, and a poll of the equally ill-informed cannot answer
the question either way.

This is carrying the otherwise commendable idea of participatory democracy into
a realm in which it certainly does not belong.

There! I feel much better now. Have a good weekend.

Leigh Palmer
Xref: sparky sci.physics:14615 rec.pets.cats:11021
From: bicker@cbnewsi.cb.att.com (The Resource, Poet-Magician of Quality)
Newsgroups: sci.physics,rec.pets.cats
Subject: Re: Radioactive Cat: How Dangerous is She?
Date: 14 Sep 92 13:40:58 GMT
Reply-To: Brian.C.Kohn@att.com (The Resource, Poet-Magician of Quality)
Followup-To: sci.physics,rec.pets.cats
Organization: The Internet

In article <1992Sep7.173452.15059@mnemosyne.cs.du.edu> snil@nyx.cs.du.edu (Sven Nil) writes:
>I love cats (have a sweet one myself) and I'm also interested in physics.
>I don't think you should worry about a radioactive cat because the only 
>humane and responsible thing to do is to take the cat to the vet and have
>it put to sleep. Your very sick cat is having a miserable life and it sure
>is very egoistic of you if you let it suffer for personal reasons. If you 
>love your cat be good to it and let it's life end the only responsible way.
>Don't confuse personal feelings with what is good for your animal. 

Such hubris!  It's rather presumptuous of you, Sven, to second guess
the original poster like this.  Many cats who are hyperthyroid live for
many years very happily.  I wouldn't want someone putting me "out of my
misery" when after just a month or two I'll be close to as-good-as-new.

Such a decision is between an owner and his/her vet, and I have had
this conversation with my vet several times.  (We've decided to try to
treat !bicker with Tapazole for now, even though he'll have to take it
for the rest of his life.  We've had kidney failure false alarms and
such and it's always come down to me making sure the vet knows that
when he gives the word, we'll put !bicker to sleep.  Thankfully it
hasn't come to that it is likely not to come to that in the short
term.)  I'm sure the original poster is indeed in contact with a vet
(afterall, how else is s/he getting all this info about radioisotope
therapy?) and any good vet would breing up the option of euthanasia if
it was appropriate.

Cats are not toys.  They're living breathing animals.  And if there is
someone willing to love them, they deserve every chance to live.

-- 
Brian Charles Kohn               using !bicker's account
Poet-Magician of "Quality"       E-MAIL: bicker@hoqax.ATT.COM
    'Hope, not fear, is the most positive advocate of action.' - S.R. Lawhead
                   Stamp Out "SO": "RP" = "Romantic Partner"
Newsgroups: sci.physics,sci.math