HDTenEightyP/NetNews huggingface dataset:
From: firth@sei.cmu.edu (Robert Firth)
Subject: Thought for the Week
Organization: Software Engineering Institute
Date: Mon, 5 Oct 1992 20:05:43 GMT

	"Have not the small Particles of Bodies certain
	 Powers, Virtues, or Forces, by which they act
	 at a distance, not only upon the Rays of Light
	 for reflecting, refracting and inflecting them,
	 but also upon one another for producing a great
	 Part of the Phaenomena of Nature?  For it's well
	 known, that Bodies act upon one another by the
	 Attractions of Gravity, Magnetism and Electricity;
	 and these instances shew the Tenor and Course of
	 Nature, and make it not improbable that there may
	 be more attractive Powers than these...

	"The Attractions of Gravity, Magnetism, and Electricity,
	 reach to very sensible distances, and so have been
	 observed by vulgar Eyes, and there may be others
	 which reach to so small distances as hitherto escape
	 Observation...

	"Now the smallest Particles of Matter may cohere by
	 the strongest Attractions, and compose bigger Particles
	 of weaker Virtue; and many of these may cohere and
	 compose bigger Particles whose Virtue is still weaker,
	 and so on for diverse Successions, until the Progression
	 end in the biggest Particles on which the Operations in
	 Chemistry, and the Colours of natural Bodies depend, and
	 which by cohering compose Bodies of a sensible Magnitude."

[Isaac Newton, Opticks, Book Three, Part I, Question 31; London 1717]
From: henryg@kullmar.se (Henry Gessau)
Newsgroups: sci.physics
Subject: Ferranti effect
Summary: What is the ferranti effect?
Keywords: ferranti
Date: 29 Sep 92 23:35:25 GMT
Organization: Firma Bo Kullmar Datakonsult


Anyone know something about the so-called "Ferranti effect"?
What is it, when/where/how does it happen, is it good/bad for
anything, etc. Anything. Everything.
-- 
Henry Gessau          henryg@kullmar.se
From: johan@blade.stack.urc.tue.nl (Johan Wevers)
Newsgroups: sci.physics
Subject: Re: Questions of transparency
Date: 1 Oct 92 12:45:45 GMT

davids@spira.bri.hp.com (david sixsmith (contractor)) writes:

>: The differential equation for an EM wave traveling in matter is given by
>: (For E only, a similiar equation holds for B):
>: 
>: \nabla^2 E = \ddot{E}/c^2 + \mu\dot{E}/\rho.
>: 
>: were \mu is the permeability and \rho the resistance per unit of length.
>: This equation has plane wave solutions:
>: 
>: E=E_0 exp(-\alpha x) cos(kx-\omega t)
>
>	2. The idea that transparent materials have gaps in their absorbtion
>	   spectra which makes them unable to absorb photons in particular
>	   frequency bands.

This is right, of course. The mechanism of the damping mechanism I described
above is that a varying E field generates a current. These equations assume
that this current can be described classically.

If you look at it more close, you see that the QM description of material
gives the corrections which others told you: not all currents behave like
they were classically.

>The proof of the pudding would be to predict transparency in a material. Does
>anyone know if this has been done ?

Yes, you must calculate which frequencies give which resonance. The better
the resonance, the better the absorption. These calculations can be done
semi-classically with (as far as I know) qualitative good predictions.

>It seems remarkable that we have here a day-to-day phenomenon which needs
>some understanding of QM to give a explanation. Does anyone know what the
>classical explanation was;

The generation of electrical currents. The explaination I wrote was classically.
Without QM, the absorption bands are not understandable.

>after all questions of lenses etc were well
>understood by Newton - did noone have any idea why glass was transparent.

He did have some difficulties with collor correction: Newton tought that it
was impossible to give the focus point of 2 collors the same position.

>Incidentally - is transparency a proof of the relative smallness of the
>nucleous ?

No, interaction cross sections have nothing to do with the size of the
pasticles (they are assumed to be point-like anyway). Cross sections can
be calculated with higher-order quantum electrodynamical corrections.
-- 
********************************************************** 
* J.C.A. Wevers                *   The only nature of    * 
* johan@blade.stack.urc.tue.nl *   reality is physics.   * 
********************************************************** 
Newsgroups: sci.physics
From: aankrom@nyx.cs.du.edu (Anthony Ankrom)
Subject: Spontaneous Symmetry Breaking
Organization: Nyx, Public Access Unix @ U. of Denver Math/CS dept.
Date: Tue, 6 Oct 92 18:36:26 GMT


 I have never read this group so I have no idea if it has been sloshed
around before, butI would like to know, in a nutshell, just what
Spontaneous SymmetryBreaking is. I read an article in a quantum chemistry
journal that discussed SSB in the visual cortex in relationship to viual
hallucinations. (I can provide a reference if it would be handy. I have
studied verylitlle quantum mechanics, but feel free to use technical
terms...) This would put an interesting perspective on my study of
neurology.

St. Anthony

--
        CH3  O            CH(CH3)2        |      dadaMatrix
           >-P-S-CH2CH2-N<            VX  |                       
    CH3CH2O               CH(CH3)2        |     aankrom@nyx.cs.du.edu
                                          | A kinder gentler lobotomy...
Newsgroups: sci.physics
From: ftdwh@acad3.alaska.edu
Subject: solutions to JD Jackson?
Organization: University of Alaska Fairbanks
Date: Thu, 1 Oct 1992 05:12:48 GMT

HELP!!!!!!

I am in desperate need of some sort solutions manual or study guide for
"Classical Electrodynamics" 2nd Edition, by J.D. Jackson, published by
John Wiley & Sons, New York.

I'm getting desperate.  I be especially pleased if such books, if any indeed
exist, were in English.

Hey, I may be goig down for the third time....


David H. at UAF  
Newsgroups: sci.physics
From: matmcinn@nuscc.nus.sg (Mcinnes B T (Dr))
Subject: Re: Understand...!!!!
Organization: National University of Singapore
Date: Fri, 2 Oct 1992 01:30:51 GMT

pratt@Sunburn.Stanford.EDU (Vaughan R. Pratt) writes:
: 
: Instead of debating the unanswerable question of whether time has any
: existence, would it not be better to focus on explanations of observed
: temporal phenomena?

No. It isn't unanswerable. If the word "existence" has any meaning at a
all, then time exists. I am amazed at all this talk of time being
"defined" by clocks, at people who speak of spacetime as a "model", at
talk of "temporal" phenomena by people who doubt that time exists.
Spacetime is not "modelled" by semi-riemannian manifolds, it IS such a
manifold.
: 
Newsgroups: sci.physics
From: ken@dakota (Kenny Chaffin)
Subject: Re: Mattel protest
Organization: U S WEST Advanced Technologies
Distribution: usa
Date: Tue, 6 Oct 1992 18:55:52 GMT

>Dear Courant Community and Friends:
>
>        Mattel has just released a new product. A Barbie doll that says
>"Math is tough".
>

	Hell, I'd have a hard time with math too without a brain and with my
plastic fingers all fused together.

come on people get a grip. Barbie is a character. Barbie does not speak for
the world, women, mattel, or mathematicians. Maybe math is hard for her.

KAC


Kenny A. Chaffin                      {...boulder}!uswat!ken
U S WEST Advanced Technologies         ken@dakota.uswest.com
4001 Discovery Drive  Boulder, CO 80303	     (303) 541-6355
 

Newsgroups: sci.physics
From: knapp@spot.Colorado.EDU (David Knapp)
Subject: Re: Cheap laser possible?
Organization: University of Colorado, Boulder
Date: Sun, 27 Sep 1992 16:46:08 GMT

In article <1992Sep25.122819.29025@alf.uib.no> sigurd@novaja.NoSubdomain.NoDomain (Sigurd Tjelmeland) writes:
>I have understood that one of the most expensive parts
>of a laser is the mirror that lets just a little light
>through. What would happen if one substituted this
>with a fully reflecting mirror with some small holes
>drilled in it. Of course this would set up some
>interference pattern on the beam, but would a laser
>beam be produced this way?
>
>Just curious,
>
>Sigurd 
>e-mail: sigurd@imr.no
>


My mail to you bounced. What you've described is 'edge coupling' and 
it works fine in many instances.  Yes, diffraction interference can be
a problem in the near field.

For a 'cheap laser' you might be interested in a nitrogen laser which requires
no vacuum or mirrors.


If you want to discuss this more, just write.
-- 
David Knapp                                      University of Colorado, Boulder
Perpetual Student                                   knapp@spot.colorado.edu
From: music@erich.triumf.ca (FRED W. BACH)
Subject: Re: STRUCTURE OF TIME
News-Software: VAX/VMS VNEWS 1.41    
Organization: TRIUMF: Tri-University Meson Facility
Date: Mon, 5 Oct 1992 19:21:00 GMT

In article <1992Oct3.203710.25949@murdoch.acc.Virginia.EDU>, crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass) writes...
>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

    While this newsgroup is not supposed to be used for the promelgation
 of religion,  what would it hurt if some knowledgeable net-historians/gurus
 etc. were to discuss the religious views of famous scientists (deceased)
 for the general edification (historical) of all of us?
    This is a topic that I would find interesting, and I'm sure there are
 lot of people out there with this special information, which may not have
 even been published.



 Fred W. Bach ,    Operations Group        |  Internet: music@erich.triumf.ca
 TRIUMF (TRI-University Meson Facility)    |  Voice:  604-222-1047 loc 278/419
 4004 WESBROOK MALL, UBC CAMPUS            |  FAX:    604-222-1074
 University of British Columbia, Vancouver, B.C., CANADA   V6T 2A3

 These are my opinions, which should ONLY make you read, think, and question.
 They do NOT necessarily reflect the views of my employer or fellow workers.
Newsgroups: sci.physics
From: ap1i+@andrew.cmu.edu (Andrew C. Plotkin)
Newsgroups: sci.physics
Subject: Re: Spin
Date: 29 Sep 92 18:17:38 GMT
	<1992Sep29.115605.10858@sei.cmu.edu>
Organization: School of Computer Science, Carnegie Mellon, Pittsburgh, PA

Excerpts from netnews.sci.physics: 29-Sep-92 Re: Spin Robert
Firth@sei.cmu.edu (445)

> And I'm still waiting for somebody to cite the passage in the Principia
> where Newton says gravity travels with infinite speed.

I haven't read it, but surely it's directly implied. The formula F = m1
* m1 / d^2 doesn't mention time, but if you had pounded on Newton a
little,  he would have admitted that he's computing the force at time T
from the distance at time T. So, more generally,
 F(t) = m1*m2 / dist(p1(t), p2(t)), where p1(t) and p2(t) are the
positions of the objects at time t. This implies, or assumes [depending
on your definition of "scientific theory" :-) ] that gravity propagates
instantaneously.

--Z

"And Aholibamah bare Jeush, and Jaalam, and Korah: these were the borogoves..."
From: bweiner@ruhets.rutgers.edu (Benjamin Weiner)
Newsgroups: sci.physics
Subject: Re: Black hole + anti-Black hole = ?
Date: 30 Sep 92 19:23:35 GMT
Organization: Rutgers Univ., New Brunswick, N.J.

John Baez writes:
>A couple of weeks ago I posted a reference to an excellent expository
>paper on this subject.  Unfortunately I no longer have the reference on
>me.  Maybe someone can mail it to John Cobb  ...

The paper was by John Preskill and is number 9209058 on hep-th, I
think.  There's some way to look up a paper by author, so that should
be enough.  It's fairly comprehensible even to theory-midgets like
myself.  Send mail to hep-th@xxx.lanl.gov with subject "help" and
NO message body.  If you screw up, don't tell them I sent you.
Newsgroups: sci.physics
From: sarfatti@well.sf.ca.us (Jack Sarfatti)
Subject: SPACETIME AND BEYOND 1
Organization: Whole Earth 'Lectronic Link
Date: Wed, 7 Oct 1992 04:08:10 GMT


The GOD(D) Drive of the most advanced Star Ships uses this psycho-geometric
mode of propulsion - requiring an Omega class bionic man at the helm...

Starting again from the cold mechanical computer-driven voice of Hawking:
Is Hawking a trance-receiver of telepatypes from the future super-
intelligence? Is Hawking a contactee of advanced extra-terrestrial
intelligence?
"If spacetime is quantized, one has to abandon the idea of a metric which
is independent of the observer ... The reason is that to determine where
one is in spacetime one has to 'measure' the metric,.and this act of
measurement places one in one of the different branches of the wave
function in the Everett-Wheeler [many worlds] interpretation."

Zeh [A German Professor of Physics at University of Heidelberg]
remarks:"This is not in conflict with the normal objectivizability of the
values of macroscopic quantities in quantum theory, since an observer
falling into a black hole certainly cannot communicate anymore with one who
remains outside of it." p.127 If my space-like quantum connection
communicator works Zeh's remark will be false so then there would be a
conflict with 'normal objectivizability' or macro objects coming into being
in the classical limit.

Zeh continues: "the global state to be described by a quantum theory of
gravity necessarily has to be correlated with (or even contain) its
observer. The same problem had arisen in connection with the nonlocality of
ordinary quantum theory. If the background geometry is unavoidably and
continuously measured ... simply by the awareness of proper time to us
observers by means of some intrinsic physiological clock [Wigner would say
"consciousness" not "physiological clock" - JS] - it represents a dynamical
superselection rule ... the nonunitarity and CPT-violation of quantum
gravity concluded by Wald (1980,81) is thus in fact simply a manifestation
of the quantum mechanical collapse (or branching) - in no essential way
different from that which leads to the 'coming into being' of other
macroscopic quantities." p.128 Direction of Time Springer-Verlag 1992

"Thes considerations which led to the conclusion that the spacetime
geometry must possess thermodynamical properties in the presence of quantum
fields, and which call for the quantization of geometry, indicate an
unexpected and revolutionary unification of fundamental physical concepts
which goes far beyond a mere unification of fields and forces. Unruh's
locally defined relation between acceleration [of particle detectors] and
temperature [of ambient thermal radiation of virtual particles in the
vacuum] may thereby turn out to be as fundamental [for the as yet unknown
quantum theory of gravity] as for example de Brogl;ie's relation between
wavelength and momentum was for quantum theory." p.128
From: ted@physics.Berkeley.EDU (Emory F. Bunn)
Newsgroups: sci.physics
Subject: Re: How old is the universe?
Date: 28 Sep 92 00:45:14 GMT
Organization: Physics Department, U.C. Berkeley.
NNTP-Posting-Host: physics.berkeley.edu

I don't know if anybody is still reading this thread, but I wanted to clarify
something regarding my last two postings.  My original source of dismay
was the fact that people constantly make assertions about "a typical
universe" without having any precise notion of how to assign probabilities
to different Universes.  I went on to make the rash, unsupported claim
that there did not exist a measure on the space of possible Universes,
and so it was completely impossible to give such statements precise
meaning.

Steve Carlip rightly pointed out that I hadn't justified that statement,
and I still can't (although I think it's true).  What I want to point out
right now is that my original claim was that the statements people
make about "typical Universes," "fine-tuning" in cosmology, and so
forth are not justified by any kind of rigorous reasoning.   All I
need to justify this claim is the fact that nobody currently knows how
to define a measure on the set of possible Universes, which is a much
weaker claim than the one I made earlier (that such a measure can't
possibly exist).  This assertion is much easier to justify:  Read the
literature all you want, and you won't find such a measure.

All right, I'm done ranting for a while.

-Ted
From: jac@ds8.scri.fsu.edu (Jim Carr)
Newsgroups: sci.physics
Subject: Re: How do you draw a straight line?
Date: 5 Oct 92 20:42:04 GMT
Reply-To: jac@ds8.scri.fsu.edu (Jim Carr)
Organization: SCRI, Florida State University

In article <5OCT199218453269@vxcrna.cern.ch> hearns@vxcrna.cern.ch (HEARNS,J./EP) writes:
> 
>ahem... This isnt my area of expertise,
>but many surveys these days are based on straight lines defined by lasers.

Yep.  You do, however, have to be careful about atmospheric effects.  I 
once saw (while spending summers surveying) a sewer pipe bend right 
up out of the ground -- almost -- before the contractor caught his 
mistake.  Thermal gradients in the pipe caused the problem; a good 
contractor will blow air through the pipe to prevent this.  

Actual survey lines still use a transit; lasers are used for distance 
measurement.  Contractors use lasers as an efficient way to carry 
slope or leveling information across a construction site.  

--
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)
From: naturman@uctvax.uct.ac.za
Newsgroups: sci.physics
Subject: Re: Simple observation about Quantum Kitty Cats
Date: 28 Sep 92 16:51:20 +0200
Keywords: Meeow again!
Organization: University of Cape Town

In article <1992Sep24.170644.337@prim>, prim!dave@germany.eu.net (Dave Griffiths) writes:
> In article <FRANL.92Sep23131031@draco.centerline.com> franl@centerline.com (Fran Litterio) writes:
>>What about the double-slit experiment?  If we don't measure which slit
>>the photon passes through, it's wavefunction passes through both
>>slits, interferes with itself, and causes that photon (and all
>>successive unmeasured-at-one-slit-or-the other photons) to strike the
>>screen only in certain areas, creating an interference pattern.
>>Put a "photon counter" at one of the slits, and the interference
>>pattern is replaced with a blob of light with a smoothly varying
>>intensity -- now the wavefunction doesn't interfere with itself,
>>because we collapse it "early" at one of the slits by counting the
>>photons there. 
> Well I keep reading about this experiment in various books, but I don't think
> it has ever actually been carried out. Not with photons anyway. The problem
> is that you don't want to "detect" it at one of the slits because that
> would destroy the photon anyway. You just want to very delicately infer
> which slit the photon went through. Perhaps someone can quote a paper which
> describes an experiment where this has been done? 
> Dave Griffiths

Hello hello, whats happening. I seem to have missed some followups to my
Quantum kitty cats posting. If you have any queries or challenges relating
to it please post directly to me as well as to sci.physics because some
sci.physics postings seem to be getting lost over here at UCT. (Could it be due
to destructive interference????!!!)

Now concerning photons going through slits, remember that photons are not
little billiard balls. I personally suspect that photons do not go nicely
through just one slit but might "bounce around"  all over the place in order to
"detect" the slits and might pass through them backwards and forwards repeatedly
, or possibly the photon is like an "active site" on some larger entity which
is spread out and can detect the slits. The very vagueness of the terms I'm
using shows how little we really understand about what photons and particles
actually are. One thing is certain, if you insist on thinking of a photon as a
little ball you are going to come up with contradictions - little balls can't
detect slits!
 
*****************************************************************************
* Baby Doc Naturman                                                         *
* USS Enterprise                           "It's life Jim,                  *
* Final Frontier                                  but not as we know it."   *
* naturman@uctvax.uct.ac.za                                                 *
*                                                       Spock of Vulcan     *
*****************************************************************************

PS "I'm da baby, gotta love me!"
From: z_arthurjk@ccsvax.sfasu.edu
Newsgroups: sci.physics
Subject: Time travel
Date: 26 Sep 92 16:26:26 CST
Organization: Stephen F. Austin State University

 I read somewhere once where time flows at a different rate near a 
black hole than it does in flat space.  What does this  mean
exactly and how would it affect a prospective time traveler?

Xref: sparky sci.physics:16005 sci.math:12767
From: rgep@emu.pmms.cam.ac.uk (Richard Pinch)
Newsgroups: sci.physics,sci.math
Subject: Re: How do you draw a straight line?
Date: 6 Oct 92 09:04:14 GMT
Organization: DPMMS University of Cambridge

If you believe in circles as drawn by a compass, but not in
straight lines as drawn by a straight-edge then you could
(i) use compass-only constructions (ii) use an inversor
linkage to turn your circles into lines.

Richard Pinch
From: bweiner@ruhets.rutgers.edu (Benjamin Weiner)
Newsgroups: sci.physics
Subject: Re: Expansion
Date: 2 Oct 92 21:09:44 GMT
Organization: Rutgers Univ., New Brunswick, N.J.

John Baez writes:
> Namely, say one takes a ball of "dust" (in the sense of
>relativity, i.e., no repulsive forces) of a given density and radius R.
>How long will it take to collapse as a function of R?
>
>Extra credit if you solve it for rotating dustballs, so that it's more
>like honest galaxies.

I bet this is just one of John Baez's homework problems and he's
trying to get us to solve it for him.  That sneaky John.  Well, it
won't work, we caught you this time!