HDTenEightyP/NetNews huggingface dataset:
From: dpbsmith@world.std.com (Daniel P. B. Smith)
Subject: Research on 60 Hz dangers (was Re: The dangers in microwaved food...)
Organization: The World Public Access UNIX, Brookline, MA
Date: Sat, 5 Sep 1992 00:47:20 GMT

In response to Bronis Vidugiris questions about studies on ELF, etc.

IEEE Spectrum, August 1990, volume 27, Number 8 has a four-part article on
this, pp 22-35.  It lists 23 epidemiological studies in progress, and
quotes experts on both sides of the controversy. One comment by Spectrum's
reporters: "Most experts we talk with privately give odds somewhere between
10 and 60 percent that within the next decade it will become cleear that
exposure to [60 Hz] fields produces significant health risks."  The
Office of Technology Assessment issued a report in 1989 that recommended
that although effects had not yet been proven, the evidence was now
strong enough to recommend "prudent avoidance" of 60 Hz fields.


-- 
Daniel P. B. Smith
dpbsmith@world.std.com
Newsgroups: sci.physics
From: qb7g6@fel.tno.nl (Maarten Landzaat)
Subject: Re: Why Do Mirrors Reverse Left/Right and Not Up/Down?
Organization: TNO Physics and Electronics Laboratory
Date: Thu, 10 Sep 1992 08:09:05 GMT

Quite a while ago, I asked the net the question mentioned in
the subject line. A little while later I detailed my question 
because so many people answered "They don't!". That question
was something like "Why do people THINK that left and right
are reversed, but not up and down?". 

Now trivedi@yukawa.uchicago.edu (Anil Trivedi) writes:

>I think this thread can use one more contribution.

>First of all, while most of you certainly know this, I should say it
>anyway: mirrors *can* produce upside-down images; it is just that
>the common plane mirrors do not do so. :-)

OK

>Now to the serious stuff. The question is: why do Left/Right behave
>differently from Up/Down? This has nothing to do with mirrors, really.

>The basic thing to understand is that neither Left/Right nor Up/Down 
>have any fixed meanings in space (the Universe).

Agreed.

>However, the notion of Up/Down is reasonably stable on the surface
>of the Earth; you have to travel far for it to shift.  It is defined
>with respect to the center of the Earth and has nothing to do with
>*your* personal orientation.

Well, someone might disagree: she could define "up" as the direction
of her body (the direction her hair points to). But this is
not very relevant.

>The notion of Left/Right, on the other hand, is defined with respect
>to your body; to use the stock market jargon, that makes it much more 
>volatile. Its meaning in space changes as you walk around. Face another 
>person: it takes no mirror to arrive at situation when *his left* is
>on *your right*. Forget another person; just turn around yourself: what 
>used to be to *your* left is now to *your* right. And so on...

You're right.

>In the (plane) mirror, the image of *your* left hand is, amazingly,
>still on *your* left. But it is the right hand of the *other guy*.
>However, as I said, you don't need a mirror for this subjective switch 
>of direction: if a real person was standing there, the "left/right"
>disagreement would be much the same. 

Yeah, but the question remains: why is there a "left/right" disagreement,
and not an "up/down" disagreement? 

> Mirrors do not reverse Left/Right
>any more than a cocktail party does.  :-)

But why do cocktail parties always turn my house upside down? (^8


-- 
Maarten J. Landzaat (analyst/programmer, bass player, Atari/midi freak)
BSO/Aerospace & Systems			Mail: Spuistraat 97
Email: maarten.landzaat@fel.tno.nl	      1012 SV  Amsterdam
Phone: +31 20 6266098			      The Netherlands
Newsgroups: sci.physics
Newsgroups: sci.physics
Subject: Re: Hidden variable theories, was: Uncertainty Princi
From: mcirvin@husc8.harvard.edu (Mcirvin)
Date: 8 Sep 92 23:13:07 GMT
 518.525@prim> <265@mtnmath.UUCP><1992Sep8.144555.455@cine88.cineca.it> <HAGERMAN.92Sep8163228@rx7.ece.cmu.edu>

hagerman@ece.cmu.edu (John Hagerman) writes:

>The word "transmission" bothers me.  Why assume that hidden variables
>are "somewhere," and that information must be "transmitted"?  Can't
>the information already *be* everywhere it is needed?  I envision a
>dual universe: in the universe we experience, events are "local" and
>hidden variables are "global"; in the dual universe, hidden variables
>are "local" and events are "global."  It seems like a mapping between
>the two would be simple.  How crazy am I?

The point is that in a deterministic, nonlocal theory, you can
do something at point A and time t that will have an effect at point B
and time t' where the distance between A and B is greater than ct.  Whether
or not you call that transmission, it's noncausal; you could then
rig things so that doing something at point A and time t will have an
effect at point A at a previous time, so long as relativity applies.

In QM, a good way to think about correlations is to treat a measurement
as acting upon the *entire* state of the system; like you say, there
isn't any well-defined "transmission" of information from one spot to
another, since you could just as well regard the measurement of spin
2 as affecting spin 1 as the reverse.  You don't have any way of
affecting how the correlated measurements come out, so causality is
preserved.  The necessity of correlation is everywhere to begin with, in
the pre-existing quantum state, and the only nonlocal thing that's 
added-- the way the correlated measurements actually come out--
is completely random.  

In a nonlocal hidden variables theory, though, everything is actually
deterministic, and it's conceivable that you *could* affect how the
correlated measurements come out.  You could then build a
device that would send messages faster than light, by affecting the
outcomes of correlated measurements.  Now, if the theory is really
supposed to accurately duplicate all the results that support QM,
presumably these hidden variables are hidden well, so that the
building of such a device is beyond our skill.  But the possibility
of such a device would be worrisome, even if it could be mapped to
a purely local process in some kind of dual space.

The worry about nonlocality is grounded in part in a desire to avoid 
causal loops of the kind implied by backward time travel.
Of course, none of this fixes the time-travel possibilities inherent
in general relativity, which are another and far more complicated
subject. 
-- 
Matt McIrvin, Cambridge, Massachusetts, USA 
Newsgroups: sci.physics
From: jcf@world.std.com (Joseph C Fineman)
Subject: Flow on the floor of a sink
Summary: Query about a familiar hydrodynamical phenomenon
Keywords: hydrodynamics, turbulence, bore
Organization: The World Public Access UNIX, Brookline, MA
Date: Sat, 5 Sep 1992 03:53:41 GMT

When the stream of water from a faucet hits the layer of water it has
created on the floor of the sink, it is surrounded by a thin disk of
water in rapid radial motion that feeds into the thicker, slower-moving
layer.  What is the nature of the transition at the periphery?  Is it
a turbulent-to-laminar transition, or is it analogous to a tidal bore?

Newsgroups: sci.physics
From: dwr2560@zeus.tamu.edu (RING, DAVID WAYNE)
Subject: Re: Why do protons outnumber antiprotons?
News-Software: VAX/VMS VNEWS 1.41    
Organization: Texas A&M University, Academic Computing Services
Distribution: na
Date: Sat, 5 Sep 1992 00:36:00 GMT

In article <26086@dog.ee.lbl.gov>, sichase@csa1.lbl.gov writes...
>But the electron and the antineutrino are not identical with one another.
>So it seems to me that you need two separate Dirac seas, each supported 
>by its own Fermi pressure, so to speak.  Even if you think of an electron as a
>rotated neutrino, then after the process you describe above, without a 
>separate electron sea the final state electron will end up in a negative
>energy state.  

Right. Dirac didn't know about neutrinos. :-)

Dave Ring
dwr2560@zeus.tamu.edu


Newsgroups: sci.physics
From: jbaez@riesz.mit.edu (John C. Baez)
Subject: Re: Did electric/magnetic symmetry "break"?
Organization: MIT Department of Mathematics, Cambridge, MA
Date: Sun, 6 Sep 92 20:15:48 GMT

Don't worry - that last post didn't end abruptly because of a massive
earthquake - it was just a gremlin eating the last line of the text!

In my previous post I wanted to note that the relationship between 
electric and magnetic charges discovered by Dirac may be the first
application of characteristic classes to mathematical physics.  I guess
this is wrong, though, since the Gauss-Bonnet formula goes back a long
way.


.
.
.
.
Newsgroups: sci.physics
From: hees@cubic.com (Phil Hees)
Subject: Re: Units (was Re: E=MC^2)
Organization: Cubic Toll Systems
Date: Tue, 08 Sep 92 20:54:07 GMT

In article <10571@sun13.scri.fsu.edu> jac@ds8.scri.fsu.edu (Jim Carr) writes:
>I do not know the weight of a stick of dynamite, but it is not pure TNT 
>anyway.  Probably around a pound or so of TNT, I would guess, but I 
>think I know someone who would know the answer.  

Actually, dynamite and TNT are totally different beasts.  Dynamite is
composed of a claylike material (fuller's earth, perhaps - I'm not
sure offhand) impregnated with nitroglycerine, while TNT is
trinitrotoluene.

Historic note: Dynamite was the invention that tamed nitroglycerine
and made it safe enough for routine use in mining and other blasting
applications (and of course, made a fortune for Alfred Nobel, the
inventor).  Nitroglycerine can be _very_ unstable, yet dynamite sticks
are almost impossible to accidentally detonate - they need to be set
off with a small explosion such as produced by a blasting cap
(typically containing mercury fulminate).

During the nineteenth century, Nobel's salesmen would give
demonstrations of the safety of their product by dropping sticks of
dynamite from a height of thirty feet onto rock or pavement, or
holding sticks in their hands and _lighting_ them!!  (Dynamite will
burn rather than explode, unless it gets extremely hot.)

Another Historic Note: After the success of nitrocelluose (guncotton,
the first smokeless gunpower) and then nitroglycerine, amateur
chemists all over Europe spent two or three decades attempting to
nitrate every known substance in search of better explosives.  A good
number of these (the resulting substances, not the would-be inventors)
turned out to be unstable, and many casualties resulted.

Unfortunately, I can't help you with the energy equivalence of either
TNT or dynamite, but TNT will definitely give the higher yield.

--
Phil Hees
hees@cubic.com
Newsgroups: sci.physics
From: bweiner@ruhets.rutgers.edu (Benjamin Weiner)
Newsgroups: sci.physics
Subject: Cosmic censorship (unsolved question)
Date: 14 Sep 92 18:20:25 GMT
Organization: Rutgers Univ., New Brunswick, N.J.

This might actually be interesting, so I retitled it.
John Baez writes:
>The genericity conditions are important because otherwise there are
>already counterexamples.  He notes, for example, that Yodzis, Seifert
>and Mueller zum Hagen have shown that "naked singularities" can occur
>during the collapse of a spherically symmetric dust cloud or for
>spherically symmetric perfect fluids. ...  He says that these are "shell
>crossing singularities," which arise from the crossing of shells of
>matter.  Their occurence is stable under spherically symmetric
>perturbations.  I guess the hope is that small NON-spherically-
>symmetric perturbations would get rid of the singularities.
>
>Does anyone here know what these naked singularities are like?  That
>is, what weird physical consequences would they have?

I didn't know that Y S & MzH had got a naked singularity for the dust
case.  That seems odd.  Wald's GR book says that the naked singularity
in the perfect fluid case is not worrisome, because it's essentially
like a shell-crossing shock wave, and the assumptions of a perfect
fluid _should_ break down at that point.  That is, reasonable
macroscopic assumptions are no longer valid (even in plain vanilla
fluid mechanics) so the perfect fluid is unphysical.  Non-sphericity
isn't needed to save cosmic censorship.  I don't know how one
wiggles out of the dust case.  I'm way out of my depth here, someone
knowledgeable please respond.

In related news, does anyone know what became of Shapiro and
Teukolsky's "black line"?
From: jbaez@riesz.mit.edu (John C. Baez)
Newsgroups: sci.physics
Subject: Re: Did electric/magnetic symmetry "break"?
Date: 6 Sep 92 18:50:28 GMT
Organization: MIT Department of Mathematics, Cambridge, MA

In article <mcirvin.715718860@husc8> mcirvin@husc8.harvard.edu (Mcirvin) writes:
>mcirvin@husc8.harvard.edu (Mcirvin) writes:
>
>>In what units?  I don't think this is the case if hbar=c=1.
>
>Aieee!  I take this back.  Mr. Bollinger is more or less right: in
>Gaussian units with hbar=c=1, the ration of the Dirac magnetic
>monopole's charge to the electronic charge is 137.036/2, or
>about 68.5.  What's really fixed, independently of the size of
>the electronic charge, is the *product* of the two quantities,
>which is 1/2 in these units.
>
>The relation is fixed by quantum-mechanical considerations, according
>to the reasoning of Dirac.  Both Sakurai's black book and Jackson
>cover this well.
> 
>-- 
>Matt McIrvin, Cambridge, Massachusetts, USA 

Honest, I took at look at Terry's strange number 63 and did a quick
check to see if it was the fine structure constant over 2, which it
wasn't.  But if he meant 68.5 then I guess it's okay.  Although as
Matt pointed out, it makes infinitely more sense to say that Dirac
arrived at a constraint on the *product* of the electron and monopole charges.
This is a statement that is independent of units. I gave an explanation of this 
effect in my series of articles on braids and quantization.   It's a nice
piece of topological reasoning - maybe one of the first uses of characteristic
Newsgroups: sci.physics
From: bhoughto@sedona.intel.com (Blair P. Houghton)
Subject: Re: Space Poop
Organization: Intel Corp., Chandler, Arizona
Date: Sat, 5 Sep 1992 18:07:43 GMT

The answer:  Quark!

				--Blair
				  "I call dibs on the two Bettys."
From: ted@physics.Berkeley.EDU (Emory F. Bunn)
Newsgroups: sci.physics
Subject: Re: Are redshifts discrete?
Date: 10 Sep 1992 18:44:16 GMT
Organization: Physics Department, U.C. Berkeley.
Distribution: world
NNTP-Posting-Host: physics.berkeley.edu

In article <5323@tuegate.tue.nl> johan@blade.stack.urc.tue.nl (Johan Wevers) writes:
>malova@venus.iteb.serpukhov.su writes:
>>
>>   Some years ago I read about discrete distribution of redshifts. 
>>   What is now? Is the idea alive?
>
>Redshift is continious: SRT tells you that the ratio of the observed
>frequency f' and the original frquency f from an object that moves w.r.t.
>the observer is given by:
>
>f'/f = \gamma(1 - v cos(\phi)/c),
>

This is certainly correct:  Redshifts can take on any of a continuous
spectrum of values.  However, I'm pretty sure that the original question
referred to reports that the actual measured redshifts of distant
galaxies are distributed in discrete clumps.

Broadhurst et al.  reported a couple of years ago on a survey they
had done of a very small-area "pencil beam" survey of galaxies.  They
measured the redshifts of all of the galaxies in their beam down to
some fairly faint limiting brightness, and found (they claim) a 
periodicity in the distribution of redshifts:  Galaxies tended to
be found at redshifts near integer multiples of some "fundamental
redshift."  I think that the fundamental redshift corresponded
to a distance of about 300 million light-years.

Within the context of the standard big bang model, this doesn't make 
sense:  Galaxies should have redshifts in proportion to their 
distances, and their distances should be randomly distributed.

These results have not been confirmed, and there have been suggestions
that the statistical significance of the effect has been greatly overestimated.
From my vantage point, which is somewhere on the periphery of this
field, it looks like most of the experts don't believe the effect is
real, although a thoroughly convincing refutation of the work
has not been offered.

-Ted

Newsgroups: sci.physics
From: exuptr@exu.ericsson.se (exuptr@exu.ericsson.se)
Newsgroups: sci.physics,sci.math
Subject: Re: Elevator mayhem
Date: 15 Sep 92 21:07:08 GMT
Organization: Ericsson Network Systems, Inc.

In article <mcirvin.716585471@husc8> mcirvin@husc8.harvard.edu (Mcirvin) writes:
>Subject: Re: Elevator mayhem
>From: mcirvin@husc8.harvard.edu (Mcirvin)
>Date: 15 Sep 92 19:31:11 GMT

>hsieh@math.toronto.edu (Paul Hsieh) writes:

>>Well, I've though about this once (not too seriously) and figure that if your
>>timing is good enough that you could jump up at the last second before impact
>>to actually reduce the speed.  Then you could end up with method 2) with 
>>lesser impact.  :)  I don't know if there is any merit to what I've just said
>>but I'm wondering if there is anything fundamentally flawed with it (besides
>>the amazing timing that would be required).

>There is a fundamental flaw... Think about what happens when you come
>back down at the end of your jump.  Remember, you've jumped off of a
>floor that is traveling downward at high speed, and you land on a floor
>that has stopped moving!  All you've done is delay the injury a fraction
>of a second. 
>-- 
>Matt McIrvin, Cambridge, Massachusetts, USA 

Yes, unless in addition to superhuman timing, you can produce enough 
acceleration to bring you to a "stop" relative to the floor you are going to.
 ----------------------------------------------------------------------------
    "This must be Thursday.  I never could get the hang of Thursdays"
                                                       - Douglas Adams
  - Patrick Taylor                                       (Arthur Dent)
    Ericsson Network Systems
    exuptr@exu.ericsson.se                       "Don't let the .se fool you"
    or exuptr@ZGNews.Lonestar.Org, exu.exuptr@memo.ericsson.se
From: jac@ds8.scri.fsu.edu (Jim Carr)
Newsgroups: sci.physics
Subject: Re: Size of neutrino
Date: 15 Sep 92 16:08:07 GMT
Reply-To: jac@ds8.scri.fsu.edu (Jim Carr)
Organization: SCRI, Florida State University

In article <9209141130.aa13761@Paris.ics.uci.edu> kibler@turing.ICS.UCI.EDU (Dennis Kibler) writes:
>Hi,
>  My seven year old is very interested in sizes and speeds of
>various things around us. Yesterday he asked me how big
>a neutrino was. I have no idea of how to answer him.
>Any help appreciated.

The neutrino is assumed to be a point particle (i.e. zero size) in the 
standard model.  Ditto for the electron, the quarks, etc.  

The best answer, however, is that all observations are consistent with 
it being a point particle -- that is, smaller than we can measure. 

You might tell him the history of thinking about this question, 
which goes back to the greeks (whence the word atom) and their 
speculation about what would happen if we cut something up into 
smaller and smaller pieces.  Is there a smallest piece?  We really 
do not know for sure, but we have narrowed down the search a lot. 
In a strict sense, we can never know that something is of zero 
size or has no constituent parts since there is always some limit 
on our observational ability.  At some point, however, theory and 
experiment (including cosmological observations) will come to a 
point where we can say we know the answer with some confidence. 
It is interesting that our present answer is that the smallest 
particle is represented by a "point", which is an idealization 
that was also invented by the Greeks -- I think. 

>A while back we had the following conversation.
>
> Son: When the astronauts go outside their spaceship,
>      they can't talk to each other.
> Me: Why is that?
> Son: Because sound goes at 600 mph and they are going
>      at 15,000 mph.
> Me: Hmnn. There isn't any air out is space.
> Son: Well--
>       that's another reason why that can't talk to each other.

And I always thought it was because they were wearing helmets ;-)

--
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: 910436a@darwin.ntu.edu.au
Newsgroups: sci.physics
Subject: Fiz. Tverd. Tela. ?
Date: 9 Sep 92 17:59:11 +0900

I am hoping someone out there who has this article in their library
would be kind enough to xerox it and send it to my address below.
I need this article really bad but sem to have great difficulty getting
it. Thanks in advance.
p/s: email my address if you intend to send so that I can return my thanks
personally.


Article details:

Authors: Guseinov NM and Seid-Rzaeva SM
Year: 1989
Journal: Fiz. Tverd. Tela.
Vol.: 31
page: 32


My address:


Ms Thilagam
Physics Department
Science Faculty
Nothern Territory University
P.O Box 40146
NT 0811
Australia


p/s 2: I know that Fiz. Tverd. Tela is a Soviet Journal catering to
physicists. 

Thanks
From: pad@galaxy.nsc.com (Paul Denny x8349)
Newsgroups: sci.physics
Subject: skin depth
Keywords: sea water
Date: 4 Sep 92 22:32:40 GMT
Organization: National Semiconductor, Santa Clara

A textbook practice question on skin depth of electromagnetic
waves that I was working on recently posed the following 
question:

find the skin depth for sea water with rho=.2 0hm.metre for
frequencies of 30KHz and 30Mhz. How practical is radio
communication with submarines?

the formula for skin depth was given as d=(2.rho/u.w)^0.5

with rho=resistivity u=permeability w=angular frequency

I plugged in the numbers and came up with d equal to 1.3m
and 41cm respectively and concluded that submarine comms
isn't practical at these frequencies which ties in with 
a vague awareness that radio comms with subs is done but
at ultralow frequencies. My problem is that there were no 
worked answers so I may have got it wrong but if I got it
right then the skin depth for light in sea water must be
in the micron range - so why isn't sea water opaque (read
where did I go wrong?:^)) 

PS My employer doesn't set me homework problems :^)
Newsgroups: sci.physics
From: jbaez@riesz.mit.edu (John C. Baez)
Subject: Re: Color of electric charges (silly question)
Organization: MIT Department of Mathematics, Cambridge, MA
Distribution: na
Date: Sun, 13 Sep 92 21:03:28 GMT

Gee, I feel deprived.  Whenever I think about elementary particles
they are a vague sort of grey or black or whatever color that is when
I do drawings in my head in which the color doesn't matter.  This is
not out of mental color-blindness, either!  When I am listening to or
playing music, or just listening to it in my head, I see all sorts of
colors.  Indeed, the imagery seems to guide my improvisation, and it
certainly increases the enjoyment.  

I would tend to think of this kind of synaesthesia as a kind of way of
increasing ones bandwidth, or getting more processing power involved. 
Seeing notes as colors is well-documented among classical composers,
all of whom have different conventions.  Those folks had perfect
pitch, or something close, so an A# would be associated with a given
color.  I have no idea what an A# sounds like, so my associations tend
to be with timbre.  

When doing mathematics I am constantly visualizing things, but never,
it seems, in color!  I used to dislike algebra because I couldn't
visualize it.  Then I learned the trick behind algebraic geometry -
algebras are spaces, projective modules are vector bundles, and so on
- so that now I like algebra and constantly visualize it in some vague
but crucial way.  

Does anyone assign colors to mathematical objects: Hilbert spaces are
blue, self-adjoint operators are red, etc.?  For some reason I would
be surprised.  But why not?  Just because most math books read by
young folks don't have colored pictures of these things?