HDTenEightyP/NetNews huggingface dataset:
From: zowie@daedalus.stanford.edu (Craig "Powderkeg" DeForest)
Subject: BAROMETERS (was Re: Subject?)
Reply-To: zowie@banneker.stanford.edu
Organization: Stanford Center for Space Science and Astrophysics
Distribution: na
Date: 1 Sep 92 12:21:51

Lots of people write:
	<stuff about people foolishly jumping out of windows>

This whole thread reminds me of the age-old physics exam question:

You are taken to a large, impressive-looking office building.  You may
wander the building and its environs at will <etc. etc.> You are given
an accurate barometer.  Your task is to determine the height of the
building.

Name at least six ways to accomplish this task. [before breakfast! ;-]

--
zowie@banneker.stanford.edu  "Tell your senator to fund the MSSTA program!"

The world would be much better if more physicists read Strunk and White, 
and more fuzzies read Tipler.  *Everyone* should read at least one 
economics text.  No exceptions.
From: bj368@cleveland.Freenet.Edu (Mike E. Romano)
Newsgroups: sci.physics
Subject: Space Poop
Date: 2 Sep 1992 23:16:43 GMT
Organization: Case Western Reserve University, Cleveland, Ohio (USA)
NNTP-Posting-Host: slc5.ins.cwru.edu


Since 1957 more than 3,300 launches have produced 7,000 trackable
objects currently in orbit, equalling approx 3000 tons of man made
material.
Of these 7000, the US and USSR have produced about 3300 each, the
rest sent up by Europe and other countries.

Only 400 of these 7000 objects are operational satellites.
The rest of this number include abandoned or non functioning satellites,
upper stages, and fragments including lens covers, separation bolts
and clamp bands.
Further, there are from 30,000 to 70,000 smaller objects but larger
than 1 cm which have not been catalogued.  Any pieces in this size
range can damage spacecraft.
Constant rain down is expected of those fragments less than 1000 km
from earths surface.

Above 1000 km in the geo stationary orbit, objects are expected to
remain for 1000 years orbitting more than 5 million times and posing
a constant risk of collision with other debris or satellites.

Interactive collisions in earth orbits will eventually generate
sufficient debris to create a dense Debris Belt and prevent further
space launchings altogether.
Some scientists predict a sufficient density of debris will begin
to reduce solar radiation reaching earth and thereby alter global
climate.
-- 
            Mike Romano     Univ. Calif. Berkeley
From: uchpcjv@Msu.oscs.montana.edu
Newsgroups: sci.physics
Subject: Re: Electrons in the body
Date: 3 Sep 92 19:52:29 GMT
Article-I.D.: Msu.00960110.2D669340
Reply-To: uchpcjv@Msu.oscs.montana.edu
Organization: Montana State University

In article <1992Aug28.040331.8765@ucc.su.OZ.AU>, yongbai@physics.su.OZ.AU (Yongbai Yin) writes:
>In article <1992Aug26.122949.10900@relay.nswc.navy.mil> bwallet@apssgi.nswc.navy.mil (Brad Wallet) writes:
>>Could anyone give me a rough estimate of the percent of mass of a human
>>body which is made of electrons? 
>
>	The number is equal to one's weight divided by the mass of two protons,
>just approximate.
>

  ROUGH ESTIMATE:  about 1/2000 of body mass.  Rought estimate.
Newsgroups: sci.physics
From: mfm0@ellis.uchicago.edu (martin frederic melhus)
Subject: Re: ELECTRON HELIX : ITS POWER AND POSSIBLITIES
Reply-To: mfm0@midway.uchicago.edu
Organization: University of Chicago Computing Organizations
Date: Wed, 2 Sep 1992 09:34:03 GMT

As a followup to Ric's analysis (which I agree with), I'd like
to add the following.  We know that B fields can't accelerate
electrons.  So, to get our stream of 850 MAmps (or whatever it
was) accelerated to nearly the speed of light would take a
massive voltage, even if we ignore relativistic effects, 
and a phenomenal amount of power.  Ignoring dielectric breakdown
for any substance that I can think of, we then find that the
B field necessary to create anything near a helix is also
absurdly large.

I would recommend that HDGARNER (sorry if I misspelled this)
take a look at the construction of a cathode ray tube, and an
e beam particle accelerator.  Those will give numbers that
are more typical of the kinds of thing that we can do.

-- 
                          | You have all the time from when you remove the |
     Martin F. Melhus     | card(s) from your hand until you put it (them) |
 mfm0@midway.uchicago.edu | on the pile to say "Last Card".  If you don't, |
                          | take your two. - Hidden texts, Book of MauMau. |
Newsgroups: sci.physics
From: bhoughto@sedona.intel.com (Blair P. Houghton)
Subject: Re: Inertial drive?
Organization: Intel Corp., Chandler, Arizona
Date: Tue, 1 Sep 1992 19:04:02 GMT

I thought every five-year-old knew how to make a swing work.

				--Blair
				  "It's just a worldline on the perturbation
				   of the geodesic of the jungle-jim."
Newsgroups: sci.physics
From: gene@andy.hssc.scarolina.edu (Eugene Rowley)
Subject: Re: Units (was Re: E=MC^2)
Followup-To: sci.physics
Organization: Humanities Computer & Soc Sciences Computer Lab
Date: Fri, 4 Sep 92 01:36:52 GMT

In article <10572@sun13.scri.fsu.edu>, jac@ds8.scri.fsu.edu (Jim Carr)
wrote:
> 
> In article <10571@sun13.scri.fsu.edu> jac@ds8.scri.fsu.edu (Jim Carr) writes:
> >
> >So 9 x 10^{13} Joules from 1 gram would be the equivalent of the energy 
> >released by 0.02 megatons (21,500 tons or 4.3 million pounds) of TNT. 
>                                            ^^^
> 
> correction, 43 million pounds, caught just after :-( I hit RETURN.
> 
> 
> --
> 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)


ummm, I think it's about 60% TNT/stick, each stick about 1/2 pound or about
140 million sticks.

Eugene Rowley                     |applications consulted on..
Night Operations Manager          |logic split..
Humanities and Social Sciences    |hands held..
Computer Lab, The University of South Carolina, Columbia, SC
------------Yes, Virginia, There is a Bible Belt!-----------------
------------I know, It Hit Me!!-----------------------------------
From: dwr2560@zeus.tamu.edu (RING, DAVID WAYNE)
Subject: Re: Length scales in physics 4 - the Planck length
News-Software: VAX/VMS VNEWS 1.41    
Organization: Texas A&M University, Academic Computing Services
Date: Wed, 26 Aug 1992 22:15:00 GMT

matmcinn@nuscc.nus.sg (Mcinnes B T (Dr)) writes...
>: radius' you want. A physical question would be: what if you compressed
>: the earth from the outside? What would be the 'internal radius' as the
>: final collapse began. The answer would be only a few times the S radius
>: by analogy with neutron star collapse.
>: 
>Sorry, I don't see how you know that it is only a few times. Won't it
>depend on the degree of compression?

Since the collapse starts when the external radius is a few times the S
radius (2M) the factor 1-2M/R is not all that different from 1, so the
internal and external radii will not differ by much.

I'm sorry I can't be more quantitative, but I'm certainly not an expert at
neutron star physics.

>: String theory doesn't really replace spacetime, but treats it as a field
>: living on the worldsheet.
>: 
>errr....meaning what? how do you "treat spacetime as a field?"

You can do the same thing with a point particle. It's path is given by
R(t) where R is a four-vector, and t is the particle's proper time, or any
other parameter. You can consider the particle to live in R space, or you
can consider R to be a field living on the one dimentional t line. Then you
can do a path integral over all paths R(t) or a functional integral over
all fields R(t).

Dave Ring
dwr2560@zeus.tamu.edu 
Newsgroups: sci.physics,sci.skeptic,alt.folklore.science
From: warren@nysernet.org (Warren Burstein)
Subject: Re: The dangers in microwaved food...
Reply-To: warren@nysernet.org
Organization: Mail to News Gateway at Wang Labs
Date: 28 Aug 92 05:48:55 GMT
Followup-To: sci.physics

kk = klaus@diku.dk (Klaus Ole Kristiansen)
db = david@euclid.JPL.NASA.GOV (David Bernath)
mbt = matmcinn@nuscc.nus.sg (Mcinnes B T (Dr))

??: there are serious health risks in eating.
mbt: There are serious health risks.
db: Health is a serious risk.
kk: Be serious.
There are serious health risks in being serious.
-- 
/|/-\/-\       In real life, the Vice President chastises Murphey Brown
 |__/__/_/     for her morals.  Bill Clinton plays the sax on "Arsenio
 |warren@      Hall."  Though "Batman Returns" is fiction, it's not too
/ nysernet.org much stranger than truth - Caryn James, The New York Times
From: jtrsmith@garnet.berkeley.edu ()
Newsgroups: sci.physics
Subject: A question on Laplace eq.
Date: 3 Sep 1992 17:31:40 GMT
Organization: University of California, Berkeley
Distribution: world
NNTP-Posting-Host: garnet.berkeley.edu

Hi, Sirs,
I have a question about if a Laplace equation 

       div grad T = 0       in a smooth enough domain,

is well-posed under following boundary condition:

    - dT/dn = a ( T*T*T*T - c),  on the domain boundary, 

    (note: T*T*T*T means T to the fourth power.)
where n is in the direction of outward unit normal along the boundary,
a, c is constant, and  a>0.

This boundary is equivalent to a radiation along boundary; heat
conducted from the domain is radiated to out side environment.

Can anybody prove that the problem is well-posed? 

If possible, please reply to this account directly. Thanks.

JTR Smith
From: sichase@csa3.lbl.gov (SCOTT I CHASE)
Newsgroups: sci.physics
Subject: Imaginary wavefunctions (was:s: Re : Everything is Unitary)
Date: 27 Aug 92 19:12:52 GMT
Organization: Lawrence Berkeley Laboratory - Berkeley, CA, USA
Distribution: na
Reply-To: sichase@csa3.lbl.gov
NNTP-Posting-Host: 128.3.254.198
News-Software: VAX/VMS VNEWS 1.3-4   

In article <1992Aug27.015029.892@uniwa.uwa.edu.au>, raistlin@tartarus.uwa.edu.au (Brett Cuthbertson) writes...
>Just a few question refering to Jack's lectures on FTL comm..ie the one
>labelled 'EVERYTHING IS UNITARY"...

>the probability is of a particle begin between 0 and infinity etc is
>always unitary...and this is worked out by generally
> 
>        psi* x psi
> 
>where psi* is the complex conjugate os psi...psi begin the wave function
>of the particle...The effectively removes any imaginary terms and makes
>the function real..This has been forced down us students this year...(
>my first year of Quantum mech..)...I just want to know what an imaginary
>state is not considered to be an option where probability is concerned..
> 
> ie why does the particle have to be always in a real state and so
>probability is conserved...

In general, wave functions are complex.  For bound state problems (particle in 
a box, etc.) you are free to choose a single complex phase, so that you can 
pick real wavefunctions if you want.  This is usually done, but there is 
no big reason other than readability.  However unbound states cannot
be so manipulated, e.g., a plane wave is normalization*exp(ipx), and the
imaginary part is crucial to getting the probability density correct.

But probabilities are real quantities.  Imaginary probabilities are 
not meaningful.  So the theory is constructed in a way such as to guarantee
real probabilities.  In fact, all measureable quantities must be real,
which you can take to be the reason that all observables correspond to 
Hermitian operators, i.e., real-eigenvalued matrices.

On the other hand, energy *can* be taken to be complex.  Then the time
dependence of the wavefunction is exp(-i(E-iw/2)t), which leads to a 
probability density with a time-dependent factor of exp(-wt), i.e., 
the particle tends to disappear with time!  That's one way of describing
dissipative processes such as the decay of a beam of particles in flight.

-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
Newsgroups: sci.physics
From: baillie@physics.ucla.edu (Grant Baillie)
Subject: Re: Facts and Values (was Where it came fr
Reply-To: baillie@physics.ucla.edu
Organization: UCLA Department of Physics
Date: Tue, 25 Aug 92 20:48:49 GMT

In article 25732@dog.ee.lbl.gov, sichase@csa3.lbl.gov (SCOTT I CHASE) writes:
> Among the rules that every graduate student in HEP knows are
[...]
> (3) 1 year = 10^7 seconds

Actually, I learnt the rule

       1 year = Pi * 10^7 seconds.

Are you using the famous "small circle approximation", where Pi is approximately
equal to 1?

Grant Baillie
Graduate Student, UCLA Physics Dept.
From: campbell@ctcvax.ccf.swri.edu
Newsgroups: sci.physics
Subject: Need Help for Laser Science project
Date: 31 Aug 92 04:21:07 GMT
Organization: Southwest Research Institute

Hello, I am Steven Campbell a 13 year old boy with a He-Ne 1.7mW laser. 
My uncle works for the big blue and has obtained this laser off a broken 
scanner. I will have a science project due this year. I would like to 
get a head start on this and obtaine some low cost ways of using this 
laser in the science fair. I am asking for some ideas of projects I
can do with this laser. If you would like to help me out, plese if you 
can give me an idea of how to build it.
Also, I would like to learn more about the power of this laser. For 
example is this the kind of laser that will give people cateracts 
if they look at this laser from a distance. 


                 Sincerly, 
                 Steven Campbell
From: jac@ds8.scri.fsu.edu (Jim Carr)
Newsgroups: sci.physics
Subject: Re: E=mc2?
Date: 31 Aug 92 15:01:23 GMT
Reply-To: jac@ds8.scri.fsu.edu (Jim Carr)
Organization: SCRI, Florida State University

In article <1992Aug31.041026.17766@nuscc.nus.sg> matmcinn@nuscc.nus.sg (Mcinnes B T (Dr)) writes:
>sajid@jam.wpd.sgi.com (Sajid Zia) writes:
>: Can somebody write to me how Einstein arrived at this
>: equation, I am extremely curious. Thanks,
>: 
>I am also very curious about the origin of the notion that nuclear
>weapons are in some special way related to E=mc^2. Even today there are
>textbooks which seem to imply that these devices operate by converting
>matter into energy. I find it hard to see how such a misunderstanding
>could have arisen.

It arose because it is true.

I would have to check in some books at home, but I think the letter 
to Roosevelt that Szilard wrote and Einstein signed made reference 
to that famous formula. 

Said simply, E=mc^2 can be taken as shorthand for the result in special 
relativity that energy and mass are different aspects of the same thing. 
The full equation is E^2 = p^2c^2 + m^2c^4, and tells you that you can 
interconvert momentum (kinetic energy) and mass -- hence kinetic energy 
can be used to create new particles, or particles can be annihilated 
at rest (as with positronium, an e+ e- pair) to produce energy. 

Nuclear devices work by converting mass (in the form of binding energy, 
since the number of protons and neutrons stays the same) into energy. 
If you weigh the pieces before and after, the masses have changed. 

The same is true for chemical reactions, but the effect is hard to measure 
since it is small -- atomic forces are weaker than nuclear forces so that 
the mass differences and energies involved are smaller.

--
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: matmcinn@nuscc.nus.sg (Mcinnes B T (Dr))
Newsgroups: sci.physics
Subject: Re: Length scales in physics 4 - the Planck length
Date: 27 Aug 92 04:25:12 GMT
Organization: National University of Singapore

dwr2560@zeus.tamu.edu (RING, DAVID WAYNE) writes:
: matmcinn@nuscc.nus.sg (Mcinnes B T (Dr)) writes...
: >: radius' you want. A physical question would be: what if you compressed
: >: the earth from the outside? What would be the 'internal radius' as the
: >: final collapse began. The answer would be only a few times the S radius
: >: by analogy with neutron star collapse.
: >: 
: >Sorry, I don't see how you know that it is only a few times. Won't it
: >depend on the degree of compression?
: 
: Since the collapse starts when the external radius is a few times the S
: radius (2M) the factor 1-2M/R is not all that different from 1, so the
: internal and external radii will not differ by much.
: 
: I'm sorry I can't be more quantitative, but I'm certainly not an expert at
: neutron star physics.
:
  OK now I see what you mean. So it seems that we agree that the
Schwarzschild radius is not a good estimate. Because I guess that the
Earth would start to collapse long long before we got down to anything
like that size.  
: >: String theory doesn't really replace spacetime, but treats it as a field
: >: living on the worldsheet.
: >: 
: >errr....meaning what? how do you "treat spacetime as a field?"
: 
: You can do the same thing with a point particle. It's path is given by
: R(t) where R is a four-vector, and t is the particle's proper time, or any
: other parameter. You can consider the particle to live in R space, or you
: can consider R to be a field living on the one dimentional t line. Then you
: can do a path integral over all paths R(t) or a functional integral over
: all fields R(t).
: 
All right, I guess you can call this "treating spacetime as a field".
But then it would seem that string theory indicates that nothing weird
happens to spacetime at small lengths: you always have a well-defined
target space.
: Dave Ring
: dwr2560@zeus.tamu.edu
From: mcs@wet.UUCP (Gil Nardo)
Newsgroups: sci.physics
Subject: Re: Gravitational lenses
Date: 31 Aug 92 08:31:26 GMT
Organization: Wetware Diversions, San Francisco

scienger@ecr.mu.OZ.AU (Christopher_Robert INNES) writes:
[ abbreviated poster request ]
> ....
> galaxy , due to einstein's general theory of relativity. I was just wondering
> if gravitational lensing has been observed by astronomers. 
> 
> Also what is the current state of dark matter theory? I mean has anymore
> evidence in the last few years come to light?
> 
> ( Knowing my luck this whole topic has probably just been discussed and 
> everyone will want to kill me when they read this )
> 

Look at page 30 of Scientific American, Sept 1992 "Special Issue".
This is an intersting article on dark matter and gravitational
distortions.  There's also a photo on page 32 by J. Anthony Tyson
displaying the gravitational lense effect.

PS. Relax, even if this topic has been discussed before nobody would
think about putting a bomb attached to your alarm clock set for 6:30
on your night table next to your bed.
-- 
Gil Nardo                  | mcs@wet.com
Migrant Computing Services | (415)664-1032
1032 Irving Street, #435   |-----------------
San Francisco, 94122       | Supernova = *!
From: dwr2560@zeus.tamu.edu (RING, DAVID WAYNE)
Newsgroups: sci.physics
Subject: Re: Redshifted light wonders
Date: 31 Aug 92 16:49:00 GMT
Article-I.D.: zeus.31AUG199211493602
Organization: Texas A&M University, Academic Computing Services
News-Software: VAX/VMS VNEWS 1.41

tolman%asylum.cs.utah.edu@cs.utah.edu (Kenneth Tolman) writes...
> 2) Is there a continuous energy change for a particular photon, or does
>it get redshifted across jumps?  Does quantum mechanics imply that
>there are only certain meaningful energy values, and as such would not a 
>photon move from one to the other?

Yes, no, yes (if the universe is closed), and no (the levels shift).

Dave Ring
dwr2560@zeus.tamu.edu
From: weemba@sagi.wistar.upenn.edu (Matthew P Wiener)
Newsgroups: sci.physics
Subject: Re: Misner et al.
Date: 31 Aug 92 13:51:51 GMT
Reply-To: weemba@sagi.wistar.upenn.edu (Matthew P Wiener)
Organization: The Wistar Institute of Anatomy and Biology
In-reply-to: matmcinn@nuscc.nus.sg (Mcinnes B T (Dr))

In article <1992Aug31.040423.15975@nuscc.nus.sg>, matmcinn@nuscc (Mcinnes B T (Dr)) writes:
>		 By the way, Weinberg's book is notorious for the claim
>that you don't really need geometry to understand GR. But somebody once
>told me that Weinberg retracted this bizarre claim. Can anyone verify?

I don't know about the latter, but his claim should be understood in
context.  He was thinking in the long run regarding grand unification,
and he took the apparent incompatibility of geometry with field theory
as grounds for pushing a field theoretic reading of GR.  How was he to
know back then that geometry was going to be so important for HEP?
-- 
-Matthew P Wiener (weemba@sagi.wistar.upenn.edu)
Newsgroups: sci.physics,sci.skeptic,alt.folklore.science
From: crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass)
Subject: Re: The dangers in microwaved food...
Organization: University of Virginia
Distribution: na
Date: Wed, 26 Aug 1992 23:47:14 GMT

In article <1992Aug26.213345.10592@lmpsbbs.comm.mot.com> bhv@areaplg2.corp.mot.com (Bronis Vidugiris) writes:
>In article <1992Aug26.022134.29183@murdoch.acc.Virginia.EDU> crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass) writes:

>)>I don't recall anything like that.  I recall now that there was a problem
>)>with cataracts at *really* high levels, but I believe that was still believed
>)>to be due to the heating effects.
>)
>)    I do not know of any such effect either, except for the fact that
>)    arms and legs and eyeballs have marvelous dimensions for developing hot
>)    spots under 2.45 GHz irradiation (especially eyeballs).  Babies
>)    heads have this same property, though most adults have heads
>)    that are too large to build up any substantial hot spots except
>)    in their eyes (c.f. Taflove and Brodwin, IEEE Microwave Theory and
>)    Techniques MTT-23:888 (1975)).
>)
>)    Of course, the input power would have to be substantial in order to have
>)    any significant heat generation.
>)
>)    Just another reason to keep kids and hammers away from your microwave...
>
>There was a case someone brought up in the talk where I heard about the topic
>(this was brought up by someone in the audience, not the speaker) where a
>hospital patient developed cataracts after exposure to a malfunctioning
>diathermy machine which put out too much power.  This was not a
>low-level/long term risk sort of thing at all.  Nor was it necessarily
>repeatable.
>

     You are probably right about heating causing this.  I suspect that
     with some of the hot spots that can be developed in eyeballs
     (combined with the scarcity of bloodflow compared to many other
     parts of the body) that heating due to a faulty diathermy machine
     could build up rapidly enough to cause the proteins in the lens
     to denature.

     As far as repeating it, let us hope not.

                                dale bass

-- 
C. R. Bass                                           crb7q@virginia.edu
Department of Mechanical and Aerospace Engineering
University of Virginia
Charlottesville, Virginia                            (804) 924-7926