HDTenEightyP/NetNews huggingface dataset:
From: johnf@uhheph.phys.hawaii.edu (John Flanagan)
Subject: Re: BAROMETERS (was Re: Subject?)
Organization: University of Hawaii, Dept. of Physics & Astronomy
Distribution: na
Date: Sun, 6 Sep 1992 11:47:24 GMT

In article <Sep03.024357.54232@yuma.ACNS.ColoState.EDU> arsmith@lamar.ColoState.EDU (Alan Smith) writes:
>[six ways to determine the hight of a building using a barometer]
>
>2)use your barometer like a meterstick (one barometer, two barometer, etc) and
>measure the barometer, multiply.

If it's a mercury-column barometer, rip the ruler off the side of the
barometer, rappel down the side of the building, and measure the height
by hand.

--John
-- 
John Flanagan                          ||"Pretty boys
johnf@uhheph.phys.hawaii.edu           || with the sunshine faces
U. of Hawaii, Dept. of Physics & Astro.|| <mumble mumble>..."
2505 Correa Rd., Honolulu, HI 96822    ||            -- My Bloody Valentine
Newsgroups: sci.physics,sci.math
From: hsieh@math.toronto.edu (Paul Hsieh)
Subject: Re: Elevator mayhem
Organization: Department of Mathematics, University of Toronto
Date: Tue, 15 Sep 92 14:33:32 GMT

In article <193c09INNb8t@stanley.cis.Brown.EDU> burton@cfm.brown.edu (Joshua W. Burton) writes:
>Sorry to post this with a new header instead of a followup; I can't seem to
>find the original article on our machine.
>
>I've been thinking this evening about how to make a best of a bad job the
>next time you push that DOWN button on the elevator and find it taking your
>instructions much too seriously.  So:  you're on the 34th floor, an even
>hundred meters up, when you hear the ~TWANG~ of four cables breaking at once,
>followed by a rusty *SCREECH* as the bolts holding two of the safety brakes
>give way from long neglect.  The remaining two brakes are both on the same
>side, and exert only enough force on the tracks to reduce your acceleration
>rate slightly and make a lot of noise.  At 8 m/s^2 (five-sixths of a gee or
>so), you have exactly five seconds to think this one through.
>
> ...  [Lots of interesting head splitting analysis omitted]
>
>1.)  Lie on the floor as proposed, supine to minimize damage to the facial
>     bones (won't you feel silly if you survive the crash only to drown from
>     a nosebleed?), with your sweater or a copy of Misner, Thorne and Wheeler
>     hastily tucked behind your noggin to minimize that localized trauma, or
>
>2.)  Do what any skydiver not bent on suicide routinely does, bending your
>     knees to absorb some impact and preparing to roll out when you hit too
>     hard to remain on your feet?
>
>Frankly, I can't decide.  Assuming the earlier poster was right about the
>springs at the bottom of the shaft---what ghoul decided to install those,
>anyway?---we have a meter, perhaps two, of bounce to deal with, and hence
>the deceleration looks to be in the 100 g range if we lie down flat.  Also,
>this way we are not as likely to die of a C2 spinal fracture or other `minor'
>injuries, and our quality of life if we survive should be greatly improved.
>On the other hand, if we crouch and roll, we get the meter of spring _plus_
>whatever bounce our own skeleton can add, and the decelerations are 
>accordingly even lower.  (Jumping is clearly going to do no good, since we
>can only get about 5% of the velocity we need to cancel the ground-floor
>reckoning:  we only guarantee that we will be at a bad angle when we hit.)
>
>Does anyone have any better intuition, further data, or clever experimental
>proposals, so we can put this grisly subject to rest?
>

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).

Paul Hsieh
From: ted@physics.Berkeley.EDU (Emory F. Bunn)
Newsgroups: sci.physics
Subject: Re: Why Do Mirrors Reverse Left/Right and Not Up/Down?
Date: 5 Sep 1992 22:45:01 GMT
Organization: Physics Department, U.C. Berkeley
Distribution: na
NNTP-Posting-Host: physics.berkeley.edu

For what it's worth, I think it would be nice if the FAQ entry on
this subject included an explanation of the fact that the apparent
left-right reversal in mirrors is due primarily to the fact that
people have a high degree of left-right symmetry.  That is, that when
you see your reflection in the mirror, you interpret the image as a person
who has been rotated through 180 degrees about a vertical axis with 
respect to you, which leads to the mapping left hand -> right hand,
etc.  That is, what the last poster said was right.

Given the high quality of the FAQ overall, I'm sure that whoever
modifies the entry will include an explanation that's much more
lucid than the one I just gave.

-Ted

Newsgroups: sci.physics,sci.math
From: jbaez@riesz.mit.edu (John C. Baez)
Subject: Re: Computability of the universe
Organization: MIT Department of Mathematics, Cambridge, MA
Date: Fri, 11 Sep 92 19:01:28 GMT

Despite strong evidence to the contrary, I know how to compute the
circumference of a circle.
From: sichase@csa2.lbl.gov (SCOTT I CHASE)
Newsgroups: sci.physics
Subject: Re: neutrinos & anti-neutrinos
Date: 9 Sep 92 21:37:54 GMT
Organization: Lawrence Berkeley Laboratory - Berkeley, CA, USA
Distribution: global
Reply-To: sichase@csa2.lbl.gov
NNTP-Posting-Host: 128.3.254.197
Summary: A question
Keywords: neutrino, antineutrino,anti-neutrino
News-Software: VAX/VMS VNEWS 1.3-4   

In article <1992Sep9.191031.17922@ucselx.sdsu.edu>, maxc0452@ucselx.sdsu.edu (Legene) writes...
>Could someone please tell me what the annihilation products
>of neutrinos and anti-neutrinos are?  I'd appreciate it ever-so-much.

It depends entirely on the energy of the particles (in the center-of-momentum 
frame) when they collide.  At low energy, it's only photons, because there 
is not enough energy to produce anything else (i.e, anything with mass).
At higher energy,  there are many possibilities.

-Scott
--------------------
Scott I. Chase			"The question seems to be of such a character
SICHASE@CSA2.LBL.GOV		that if I should come to life after my death
				and some mathematician were to tell me that it
				had been definitely settled, I think I would
				immediately drop dead again."      - Vandiver
Xref: sparky sci.physics:14565 sci.misc:1610
From: w.p.coyne@newcastle.ac.uk
Newsgroups: sci.physics,sci.misc
Subject: Time dilation, photons and W,Z.
Date: 13 Sep 92 13:58:17 GMT
Reply-To: w.p.coyne@newcastle.ac.uk
Organization: Chemical & Process Engineering Dept, University of Newcastle, UK.


    subject:- What effect if any does time dilation have on photons, given
              that photons in a vacuum travel at the speed of light and
              those not travel slower?

GIVEN
 The life-span of a virtual particle is related to its mass, the more
massive it is the shorter its lifespan, so the shorter the distance
over which the force is able to interact.

AND GIVEN
  In relativity it has been shown using short lived sub-atomic particles 
that as it
gets closer to the speed of light, time dilation results in it surviving
for a longer time (in the view point of outside observers).

THEN
   These two bits of information got me wondering about photons and 
gravitons.  Do photons (and virtual photons ) behave 
differently when they are travelling at light-speed
from when they travel at less than light speed?

   I don't remember reading about the effects of time dilation on gluons,
and the W, Z particles.  They have masses so obviously don't travel at
light speed, do they all travel at the same speed?   If not and they
travel at significant percentages of lightspeed, the effects of time
dilation will have significant effects on the distances they are able to
travel?

   An idle thought:-
      It's odd to think that if you rode on a photon (yes I know you can't
      but treat this as a thought experiment) you travel through the
      vacuum between stars at light speed, so it appears instantaneous to
      you.  When you travel through the 5000km atmosphere of a planet you
      slow down to less than light speed.  So the short distance through
      the atmosphere seems to take longer than the vast distance between
      the stars!
              (If i'm wrong in this, please say so)
From: ric@hpspdla.spd.HP.COM (Ric Peregrino)
Date: Fri, 4 Sep 1992 18:55:58 GMT
Subject: Re: Radar Invisibility
Organization: HP Stanford Park - Palo Alto, CA
Newsgroups: sci.physics


It's a quantum mechanical process really. Macroscopicly it's just I^2 R
losses in the windings, I^2 R losses for the eddy currents, hysterisis
losses (for AC, not DC), dielectric losses, losses due to the complex
part of the permeability (I don't think this is the same as hysterisis
losses), radiation losses. I'm at a loss to come with any more.

--------------------------------------------------------------------------
Ric Peregrino     c/o Hewlett Packard Co.        I represent only myself
ric@spd.hp.com    1501 Page Mill Rd. Bldg. 5M    I may be wrong, maybe not
415-857-7526      Palo Alto, CA 94304            Do DC photons exist?
--------------------------------------------------------------------------
Newsgroups: sci.physics
From: agc@bmdhh298.bnr.ca (Alan Carter)
Subject: Re: Why Do Mirrors Reverse Left/Right and Not Up/Down?
Organization: BNR-Europe-Limited, Maidenhead, England
Date: Thu, 10 Sep 1992 08:19:25 GMT

In article <BuC9F9.KIn@world.std.com>, jcf@world.std.com (Joseph C Fineman) writes:
|> Right!  Here is another web of words:  Mirrors do not reverse left &
|> right *or* up & down: they reverse forward & backward (or, more precisely,
|> they reverse the direction perpendicular to them: a horizontal mirror
|> *does* reverse up & down).  But people in real life exchange their
|> front & back sides by rotating, not by popping thru themselves; therefore,
|> we say "the person in the mirror has raised his left hand, whereas I
|> have raised my right hand", rather than "the person in the mirror has
|> his face on the back of his head, rather than...".  In the case of a
|> printed page, if the page is transparent, so that you can read it in the
|> mirror without turning it over, then it appear unreversed both in the
|> real world and in the mirror; if you have to turn it over, then *you*
|> make the choice of reversing left & right or top & bottom, and you
|> choose the former because you have the person in the mirror in mind.

The key point here is how we do the decentreing trick of imagining 
ourselves being the person in the mirror, so that we can compare 
ourselves with them. The way that we would get to where that person
is, is by walking around the mirror, making a half turn on the way.
We would not normally make the journey by diving over the top of the
mirror. If we did we might say that mirrors reverse up and down, but
not left and right. 

Likely the first generation of children brought up in zero G will go
both ways depending on which is more convenient and will not be able 
to believe that mirrors sometimes reverse left and right and sometimes
reverse up and down. They will simply realise that mirrors do not
reverse anything at all, and will regard their groundhog ancestors'
beliefs on this matter as more evidence of what gravity does to the brain.

   Alan

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   Maidenhead itself is too snobby to be pleasant. It is the haunt of the
   river swell and his overdressed female companion. It is the town of showy
   hotels, patronized chiefly by dudes and ballet girls. 

   Three Men In A Boat, Jerome K. Jerome, 1889
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Newsgroups: sci.physics
From: firth@sei.cmu.edu (Robert Firth)
Subject: Re: Report on Philosophies of Physicists
Organization: Software Engineering Institute
Date: Fri, 11 Sep 1992 16:57:57 GMT

In article <9209110902.AA29961@ucbvax.Berkeley.EDU> nicho@vnet.ibm.com writes:

>   Aha ! Now we're making progress. You appear to equate 'Western' modes
>of thought with boolean logic. This is a naive view. Whilst true that
>boolean logic has been developed to a high degree in 'western' societies,
>it is by no means the whole.

Not least because what we in the West call "Boolean" logic was developed
also to a high degree in eastern societies, especially India and China.
From: sichase@csa2.lbl.gov (SCOTT I CHASE)
Newsgroups: sci.physics
Subject: Re: Question of Theory of Everything (or Grand Unified theory)
Date: 9 Sep 92 19:56:56 GMT
Organization: Lawrence Berkeley Laboratory - Berkeley, CA, USA
Distribution: na
Reply-To: sichase@csa2.lbl.gov
NNTP-Posting-Host: 128.3.254.197
News-Software: VAX/VMS VNEWS 1.3-4   

In article <8SEP199221412082@zeus.tamu.edu>, dwr2560@zeus.tamu.edu (RING, DAVID WAYNE) writes...
>matmcinn@nuscc (Mcinnes B T (Dr)) writes:
>>>Now: is it not truly astounding that the complexity of the universe
>>>is so precisely calibrated to the intelligence of homo sapiens?
> 
>Not at all. Life evolved intelligence because understanding nature is
>an advantage. And _somebody_ had to be the first to fully understand nature.
>Now you might think it astounding that you are alive at the same time as
>Witten (:-D) but that is not surprising either, because most of the people
>ever to have lived are alive today.

There was recently a discussion of this (was it sci.skeptic?) - one estimate
which was posted is that the total population over all human history is
roughly 100 Billion (of course it depends on when you start counting).  If
this is even roughly correct, then your statement is incorrect.

> 
>Which reminds me... Consider Galileo, Newton, Einstein. There should
>be at least 3 people alive today as brilliant in physics as they were!

Galileo and Newton were bright, but they were also lucky to be born when 
you could gain fame and fortune for say, looking through a telescope
and discovering sun spots, moons, etc.  They were both certainly visionaries, 
but I don't know if they were any more intelligent than today's luminaries.
Einstein is another matter - I think that he is a good example of extreme
genius performing unexpected nontrivial feats in a time when cutting-edge
experimental data was much harder to generate, the necessary mathematics
was much more sophisticated, and the "easy" things had already been done.

-Scott
--------------------
Scott I. Chase			"The question seems to be of such a character
SICHASE@CSA2.LBL.GOV		that if I should come to life after my death
				and some mathematician were to tell me that it
				had been definitely settled, I think I would
				immediately drop dead again."      - Vandiver
Organization: Penn State University
Date: Sun, 13 Sep 1992 16:50:03 EDT
From: <MRG3@psuvm.psu.edu>
Newsgroups: sci.physics
Subject: Re: Lebesgue integral (was: Couple of questions
 <18neu6INN32k@function.mps.ohio-state.edu>
 <1992Sep10.173619.24343@galois.mit.edu>
 <18q2s0INNmb5@function.mps.ohio-state.edu> <10712@sun13.scri.fsu.edu>

Jim Carr writes
>In article <18q2s0INNmb5@function.mps.ohio-state.edu>
>edgar@function.mps.ohio-state.edu (Gerald Edgar) writes:
>>
>>Now all you have to do is convince the physicists that their
>>Ph.D. students (at least) should study the Lebesgue theory.
>
>Good luck with the "up to their elbows in pump oil" crowd!
>
>Theoretical students should definitely have a grounding in more than the
>usual advanced calc and complex variables courses.  Or is the problem
>that Lebesgue measure theory is not taught in the advanced calc courses
>taken by many undergrad physics majors?

As an undergrad, my real analysis course seemed basic nuts and bolts epsilon
delta approach to calculus.  (i.e. BORING)  I don't remember any there being
any significant reference to topology or measure theory.  I get the impression
that most undergrad complex variables courses are straight out
of Churchill, with emphasis on evaluating nasty integrals with
elegant selection of contours.  As a grad student, however, I sat in on
the math grad sequence in analysis (real+complex, functional). I found the
material fascinating and relevant.  So why limit the young physicist to only
Legese measure theory?  After all, are the only spaces of interest in Physics
 R:n?

-mike gallis
From: daryl@oracorp.com (Daryl McCullough)
Subject: Re: Hidden variable theories, was: Uncertainty Princi
Organization: ORA Corporation
Date: Mon, 14 Sep 1992 23:20:56 GMT

In article <278@mtnmath.UUCP>, paul@mtnmath.UUCP (Paul Budnik)
writes:

>> In order for there to be a transmission of information, there must be
>> a sender and a receiver of the information. Information is transmitted
>> to the extent that there is a correlation between the choices made by
>> the sender and the results observed by the receiver.

>I do not see how choices are involved. Weather satellites transmit large
>quantities of information about the atmosphere and oceans to ground stations.
>Nobody chooses what that information is. The only choices are where the
>camera is pointed and what parameters it is set at.

The choice for the camera is the pattern of light falling on the lens
of the camera. It happens to be that for a weather satellite, that
choice is made by light received from the Earth, but that doesn't have
to be the case. An astronaut could project light directly into the
lens and send different signals.

The information transmitting capacity of a device is independent of
what information the device happens to be transmitting, and to
calculate this capacity, it is necessary to figure out what the
manipulable variables on the transmission side are.

>> Encrypted messages *can* (and are) used to communicate.

> They can only be used to communicate if the receiver has the the
> decryption key.

No, that's not true. I can tell the receiver: "I'll send the same
message twice to indicate `yes', and two different messages to
indicate `no'." Then as long as the encryption device encrypts the
same messages in the same way, we can communicate without knowing how
the encryption device works.

Anyway, the existence of a decryption key *before* the transmission
makes the difference between sending information and not. If the key
is created as you go along, then no information is transmitted.

Daryl McCullough
ORA Corp.
Ithaca, NY
From: llew@coal.WPI.EDU (Lok C. Lew Yan Voon)
Subject: Elasticity Theory
Organization: Worcester Polytechnic Institute
Date: Sun, 6 Sep 1992 00:00:30 GMT

I'm looking for references which go beyond linear elasticity theory.
How about a thermodynamic approach for general elasticity?
From: mcirvin@husc8.harvard.edu (Mcirvin)
Newsgroups: sci.physics
Subject: Re: Rotating Bucket of Water in a Gravitation Field...Part #2
Date: 5 Sep 92 15:26:26 GMT

ric@hpspdla.spd.HP.COM (Ric Peregrino) writes:

[about the Mach's principle gedankenexperiment in which one rotates
all the stars and (perhaps) changes which frames are inertial]

>I think this is wrong. Say there was only one star, which was just a
>flashlight (not much mass compared to the Earth). Now if the rest of
>the empty universe, containing this flashlight, spun around the Earth,
>why would you expect to see the water move in the bucket? This flashlight
>has very little mass and is far from the Earth; it's really just a marker.

The idea behind Mach's principle is that just one star wouldn't do it--
it takes a universe full of matter surrounding the bucket to define what
the inertial frames are, or at least a very large amount of matter.  In
that case you certainly can't say, in the context of general relativity,
that the gravitational effects of all this matter are necessarily small. 
In Newtonian gravity you might be able to argue that the rest of the 
universe, being more or less spherically symmetric, exerts little or no
force on the water in the bucket.  But some GR effects, like gravitational
time dilation, scale and add up like the *potential* rather than the
force; a thick spherical shell might well have some effect on stuff
inside it.

Mach's principle was an important motivating idea for Einstein, and some
aspects of it do show up in general relativity:  rotating objects "drag"
the inertial frames slightly as they rotate, so the definition of an
inertial frame does depend on the distribution of matter to some extent.

On the other hand, in GR you can have solutions like Minkowski space,
in which there is a clear distinction between inertial and non-inertial
frames, but no matter.  A small test bucket in Minkowski space would
react differently to rotation and non-rotation, without any other matter
present.  This solution requires special boundary conditions, though.
One way you might think of Mach's principle is the idea that a large
quantity of matter can act in lieu of boundary conditions.

I think that the general validity of Mach's principle in GR is still a
matter of debate.
 
-- 
Matt McIrvin, Cambridge, Massachusetts, USA 
Newsgroups: sci.physics
From: bhoughto@sedona.intel.com (Blair P. Houghton)
Subject: Re: Wave/particle duality
Keywords: photon,particle,dual slits,interference,quantum waves
Organization: Intel Corp., Chandler, Arizona
Date: Sun, 13 Sep 1992 22:10:48 GMT

In article <xjeldc.41.716385288@lustorfs.ldc.lu.se> xjeldc@lustorfs.ldc.lu.se (Jan Engvald LDC) writes:
>In article <BuDIn8.C6J@nntp-sc.Intel.COM> bhoughto@sedona.intel.com
> (Blair P. Houghton) writes:
>>That is, they are particle-like in that they occupy small
>>regions of space and time; they are wave-like in that they
>>interfere.  Their waveness has nothing to do with whether
>>they are waves or not, since it's a waveness of their
>>aggregate distribution, not of individual particles.  They
>
>This because I believe that particles ALWAYS behaves as waves.

Feynman's point, which he almost lets be swallowed by the
usuall mess of qualifications for the experiment, is that
QM objects are neither particles nor waves, but at certain
times they have behaviors which resemble those of particles
and/or waves.

The "interference" isn't an interference, it's an intrinsic
characteristic of the object, determined by the form of the
wavefunction of the object.  Electrons, for example, have
a wavefunction with exp(i * p . r / h_bar) as a factor, where
p is the momentum vector, and r is the position vector of
the electron with respect to the source (or the slit,
depending which side of the wall you're on<<---see this?
this is the sort of digressive qualification of the description
of QM that distracts you from the mathematics and gets you
confused by thinking about the setup of gedankenexperiments!)

That factor is a complex sinusoidal function, which is
what travelling waves look like.

This is a very simplified nudge towards understanding what
is going on.  Read Feynman's Lectures on Physics, chapters
1-3 of volume III, carefully, and if you start thinking
of particles as waves go back and read them again.

				--Blair
				  "If you fire photons of high
				   enough energy at me, I become
				   uncertain."