HDTenEightyP/NetNews huggingface dataset:
From: Dalcio.Dacol@bbs.oit.unc.edu (Dalcio Dacol)
Newsgroups: sci.physics
Subject: Re: Blue Sky
Date: 23 Jul 92 22:39:10 GMT
Organization: Extended Bulletin Board Service

In article <1992Jul23.171544.6664@trentu.ca> pyacm@trentu.ca (A Colin Morton) writes:
>In article <1992Jul23.010953.6388@math.ucla.edu> barry@arnold.math.ucla.edu (Barry Merriman) writes:
>>In article <10018@vice.ICO.TEK.COM> hall@vice.ICO.TEK.COM (Hal Lillywhite)  
>>writes:
>>> In article <9930@sun13.scri.fsu.edu> jac@ds8.scri.fsu.edu (Jim Carr) writes:
>>> 
>>> ....
>>> >George did that routine before blue-corn became popular enough to 
>>> >show up as corn flakes as well as tortillas, or squid-ink pasta made 
>>> >it into american grocery stores.  Interesting that there are blue birds 
>>> >and flowers but not blue animals; where is a biologist when we need one! 
>>> 
>>> And I find it peculiar that although there are blue birds, there are
>>> no blue raptors that I know of.  Can you imagine the advantage a sky-
>>> blue hawk would have?  His prey would have a very difficult time seeing 
>>> him until it was too late.  I wonder why such an obvious advantage 
>>> seems not to have developed.
>>
>>Actually, he should be blue on the bottom and dark on top,
>>so that he ends up blending in when viewed from above or below.
>>Thats "why" fish are silver on the bottom and dark on top, perhaps
>>
>Most raptors are, in fact, white or very light gray on their undersides,
>with mottled brown top coats.  In most parts of the world inhabited by
>hawks and the like, partly cloudy or hazy days far outnumber the
>perfectly clear ones, so this actually works better than a blue
>underside would -- white shows up less distinctly on a blue background
>than vice versa.
>
>Colin.

	The point, it seems to me, is that any bird, no matter what
color, when seen from below against the day-time sky is going to look
like a darkish sillouete. since it is mostly backlit. The brownish-gray
color does offer some camouflage advantage because in the final
approach, hawks that hunt in open areas come in at very shallow grazing
angles and so the bcakground, frrom the prey's point of view is either
a terrestrial landscape (low hills, bushes, etc) or the distant
horizon, which in general is not blue, but somewhat grayish (sunset and
down excluded).
	Incidentally, birds are animals and therefore there are blue
animals. There are also blue lizzards, but in mammals it is quite rare
indeed. In mandrils, a large african baboon, there is blue pigmentation
on the face.  One should also mention that the blue in bird feathers is
not produced by pigments, its origin is the same as the blue of the
sky, namely Rayleigh scattering by tiny air bubbles in the feathers.
--
   The opinions expressed are not necessarily those of the University of
     North Carolina at Chapel Hill, the Campus Office for Information
        Technology, or the Experimental Bulletin Board Service.
           internet:  bbs.oit.unc.edu or 152.2.22.80
Newsgroups: sci.physics
From: jbaez@riesz.mit.edu (John C. Baez)
Subject: Re: Trapped!
Organization: MIT Department of Mathematics, Cambridge, MA
Date: Fri, 31 Jul 92 16:55:02 GMT

I found out just now that Smolin has already published his views on 
Darwinian Cosmology in a paper entitled "Is the Universe Alive?"
(roughly) in the Journal of Classical and Quantum Gravity, 1992,
vol. 9 p. 173.

Newsgroups: sci.physics
From: bweiner@ruhets.rutgers.edu (Benjamin Weiner)
Newsgroups: sci.physics
Subject: Re: ... an infinite mesh of 1ohm resistors ...
Date: 28 Jul 92 20:11:35 GMT
Organization: Rutgers Univ., New Brunswick, N.J.

Adam Costello writes:
>But I think you are missing the point of the second post.  The "solution"
>involved imagining that you could inject an amp of current into a network
>of resistors.  No capacitors!  Where is the charge supposed to go? ...

Argh, you nudniks.  Imagine a very large square grid of resistors,
say 1000 on a side.  Now connect the edges of the network to ground.
Consider point A, which is at the center of the network, and point B
which is one resistor to the right.  
1.  Attach a 1 amp source to point A.  The current flows out of A
to the edges of the network (ground).  By symmetry, 1/4 amp flows
out through each resistor attached to A, so 1/4 amp goes to B.
2.  Attach a 1 amp sink to point B (negative voltage).  B is almost
exactly in the center so again symmetry arguments apply, and 1/4 amp
comes in from point A.

Superposing the two gives the solution as before: 1 amp into A and out
of B, 1/2 amp through resistor AB, so the resistance is 1/2 ohm.
The answer to "where does the current go?" is: in the limit, it goes
to infinity.  That may seem odd, but remember that anything involving
an infinite grid is already faintly ill-defined.

Ben
From: bweiner@ruhets.rutgers.edu (Benjamin Weiner)
Newsgroups: sci.physics
Subject: Re: non-orientable cosmology
Date: 28 Jul 92 19:16:12 GMT
Organization: Rutgers Univ., New Brunswick, N.J.

Re: G.F.R. Ellis's speculation that the Universe is small and we've
already seen around it many times: 

I understand that Ellis is considering some kind of nontrivial 
topology (though I don't understand the topology!).  Can one
of you speculate on what this would do to the volume element as
a function of r?  It seems to me that this is one of the stronger
observational tests of such a notion (e.g. in the conventional
topologies the observed volume element limits the curvature to
be fairly close to flat, otherwise things would happen with galaxy 
counts that we don't in fact see.)

Ben
Newsgroups: sci.physics
From: mroussel@alchemy.chem.utoronto.ca (Marc Roussel)
Subject: Re: "What's New" July-24-1992
Organization: Department of Chemistry, University of Toronto
Date: Mon, 27 Jul 1992 03:19:19 GMT

In article <JMC.92Jul25123947@SAIL.Stanford.EDU> jmc@cs.Stanford.EDU writes:
>The reason for the space station is only marginally science and
>even more marginally prestige.  The space station is a start on
>human expansion into the solar system.

    The point that the various physical (and other scientific)
societies are trying to make is that the space station as currently
designed is not good for anything, including space exploration or
"expansion into the solar system", whatever that means.

>It may not be the best design, but
>it's the only design we have

     Designs are a dime a dozen; if nothing else there is the original
design.  Our governments should either commit the funds to build a
proper platform for something (be that space exploration or fundamental
research or engineering work) or they should just admit that they have
no commitment to the project and cancel it.

				Marc R. Roussel
                                mroussel@alchemy.chem.utoronto.ca
From: emarkp@ocf.berkeley.edu (E. Mark Ping)
Newsgroups: sci.physics
Subject: Re: Relativity
Date: 24 Jul 1992 19:52:44 GMT
Organization: U.C. Berkeley Open Computing Facility
NNTP-Posting-Host: plague-ether.berkeley.edu

In article <9207240533.AA11483@Ra.MsState.Edu> rsf1@Ra.MsState.Edu (Robert S. Fritzius) writes:
>Cross-posted from alt.sci.physics.new-theories
> 
>In article <1992Jul22.150401.15820@news.endg.convex.com> Steve Warren
>writes:
> 
>>The biggest practical reason that FTL travel is impossible (unless new
>>discoveries in physics are made - that are not anticipated right now)
>>is because of the mass increase phenomenum.  This has been repeatedly
>>verified experimentally, . . .
> 
>In 1908 Swiss physicist Walter Ritz proposed an emission theory of general
>electrodynamics(1) in which the mass of charged bodies do not increase
>toward, relativistically, but rather that their masses remain constant and
>the electrodynamic acceleration forces approach zero.
> 

[explanation deleted to make newsreader happy]

>How do we unambiguously determine whether mass increases relativistically
>or whether electromagnetic forces decrease relativistically?
> 
> 

  Someone correct me if I'm wrong (I'm just a physics *student*) about
this.  When particles get zinging around near c in, say, the Bevatron here
at Berkeley, not only does it require more energy to accelerate them, but
when they smash into something (i.e. an antiparticle or something like that)
the energy released is significantly *more* than can be acounted for by the
particles rest mass (by a factor of several hundred if I remember
correctly).  I doubt Mr. Ritz accounted for that.  After all, his time was
long before particle accelerators.
-- 
Another student, lost in the sea that is called Bezerekely.  His name?
E. Mark Ping
emarkp@ocf.Berkeley.EDU

  "Stand aside, I take large steps."  --Michael Dorn
  "Say, that's a nice bike." --Cyberdyne Systems T-1000
  "Pituita es."  --Unknown Latin Scholar
Newsgroups: sci.physics
From: clwu@Uz.nthu.edu.tw (Ching-Long Wu (PHYS U790315))
Subject: The Bubbles
Organization: National Tsing Hua University (HsinChu)
Date: Tue, 28 Jul 1992 10:51:01 GMT

Hello everyone!
   I am quite interested in the behavior of the bubbles that floating
on water's surface. I have several questions:

1. What's the shape of it? Is it a perfect semi-sphere?
2. Why does it break? And what's the machanism of it's breaking?
3. I suppose there are some relation between a bubble's 'life' and 'size'.
   I think of an experiment like this:
                                                                  
                 meter                //                                   
            |++++|++++|++++|++++|+++  ||     |                        
            |-----------O---O---------||-----|                        
            |         bubbles    O    ||     |                          
            |                   O     //     |                        
            |                       O        |                                                                            
            \--------------------------------/                                                                                                
   When a bubble appears on the surface, mesure its diameter immediately and
start the time counting till it breaks. Has any one done such kind of
experiment? What's it look like?

4. What if the bubbles are floating in the air? If there is no gravitation,
will them break?

   I hope you are also interested in these questions...

Dragon
clwu@Uz.nthu.edu.tw
                                                               
Newsgroups: sci.physics
From: bj368@cleveland.Freenet.Edu (Mike E. Romano)
Subject: Low Tech is Best
Organization: Case Western Reserve University, Cleveland, Ohio, (USA)
Date: Wed, 22 Jul 92 23:51:09 GMT


I heard somewhere that certain engineering solutions which appear primitive
actually superior in efficiency to modern ones.
One example:  the Amish farm method of transferring work power via a stiff
steel wire up to half a mile long, using rocker arms, and off center wheels,
to transfering drive from either a water wheel or a wind mill distant from
the farm's workshop.
That this method transfers work energy much more efficiently than an electric
line would, since voltage drops as distance of electric cord increases.
(I am not including energy loss due to conversion of water power to electric,
etc.).
In other words, is the bailing wire superior to electric wire in this case?
-- 
            Mike Romano     Univ. Calif. Berkeley
Newsgroups: sci.physics
From: Ari.Huttunen@hut.fi (Ari Huttunen)
Subject: Relative uncertainty principle?
Organization: Helsinki University of Technology, Finland
Distribution: sci
Date: 31 Jul 92 03:10:10

DISCLAIMER: I am not a phisicist and I mostly know the Schroedinger equation
            by sight only. There are perhaps great mistakes in the text below,
            but in that case I would like to know them and be content.


Heisenberg says:
	"It is impossible to know simultaneously and with exactness
	 both the position and the momentum of a particle."

What if we say:
	"It is impossible to know simultaneously and with exactness
	 both the personality of the photon as a wave and as a particle."

Consider a two-slit experiment (like the one shown in the July issue
of Scientific American that I have lying on the table). If you observe/know
the photon all the way from the light source, through one of the slits and
to the detector, you know with exactness that the photon is indeed a particle,
but the wave-personality has become uncertain. Thus you cannot detect any
interference pattern. (Look at the left of the picture labeled "Revealing
the Split Personality of Light" in the above mentioned magazine.) If you
wait longer and observe only the effect of photons hitting the detector,
you will notice an interference pattern. You now know the photon is a wave,
but you have lost knowledge of its particle-quality, thus you don't know
which slit it went through. (At the right of the picture.) If you observe
the particles hitting the detector but not which slit they went through, you
will have some knowledge of the particle-quality (you observe distinct
particles) and some knowledge of the wave-quality (you can calculate the
interference pattern by observing very many of the distinct particles.)

But why did I write 'relative' in the subject?

Think about how the laboratory is observing the photon (as a wave). The two
slits are uncertain through which of them the individual photon went through.
Now, think what the photon observes. The photon knows exactly where and when 
it goes. It is the laboratory that is affected by uncertainty. The photon 
would see the two slits so vaguely that they would seem to be only one slit, 
through which the photon goes.

Both the wave-quality of the photon and the location in space of the slits
are large scale phenomenon, the particle-quality of the photon and its
exact path through the slits are small scale phenomenon. You cannot measure
both small and large scale events exactly.

ps. Where can I get a queue number for new explanations of quantum physics? ;-)
--
...............................................................................
Ari Huttunen                                         You don't miss water
                                                       until the well runs dry.
From: aephraim@physics.Berkeley.EDU (Aephraim M. Steinberg)
Newsgroups: sci.physics
Subject: Re: Bell dethroned
Date: 30 Jul 92 00:24:34 GMT
Organization: University of California, Berkeley
NNTP-Posting-Host: physics.berkeley.edu

In article <Jul.29.19.10.15.1992.21798@ruhets.rutgers.edu> bweiner@ruhets.rutgers.edu (Benjamin Weiner) writes:
>Finally, aficionados of EPR-tricks should read Greenberger, Horne,
>Shimony, and Zeilinger's paper (Am J Phys 58, 1131) along with
>Mermin's treatments (Am J Phys 58, 731; PRL 65, 3373) which show that
>it is possible to construct a simple system of 3 particles of spin 1/2
>and make certain measurements such that QM predicts a -1 correlation
>and hidden-variables predict a +1 correlation.  That is, one could
>never trick up hidden variables to reproduce QM in this case.  I
>rather doubt anyone will be able to devise an experiment that 
>reproduces this system, but I could be wrong.
>

Actually, though that example is certainly much more striking as a 
theoretical discussion of how QM differs from local realistic theories,
people who've looked at it closely tell me that in any real experiment
it would turn out to require even higher detection efficiencies than
the standard Bell Inequalities.
As far as devising an experiment, that's not nearly so hard as actually
performing it :-).  Yurke and Stoler, in particular, have come up with
a scheme for doing something along GHZ lines, if I'm not mistaken.
PRL in the past few months, I think, maybe a little older...



-- 
Aephraim M. Steinberg                    | "WHY must I treat the measuring
UCB Physics                              | device classically??  What will
aephraim@physics.berkeley.edu            | happen to me if I don't??"
                                         |       -- Eugene Wigner
Newsgroups: sci.physics
From: love@geophysics.harvard.edu (Jeff Love)
Newsgroups: sci.physics
Subject: Re: Blue Sky
Date: 26 Jul 92 23:36:47 GMT
Reply-To: love@geophysics.harvard.edu
Organization: Dept. of Earth & Planetary Sciences, Harvard University

Ok, so Rayleigh scattering explains why the sky is blue: blue light is
scattered more than red light. I guess I don't like this explanation since
I don't know why  Rayleigh scattering preferentially scatters blue light.
Is their a **classical** (i.e. no QM) explanation for this effect? If DaVinci
got it right as Jackson claims in his book, then there must be a classical
arguement.

Jeff Love
Newsgroups: sci.physics
From: allenk@harry.ugcs.caltech.edu (Allen Knutson)
Subject: Re: Blue Sky
Organization: California Institute of Technology, Pasadena
Date: Wed, 22 Jul 1992 04:44:17 GMT

andrew@rentec.com (Andrew Mullhaupt) asks "Mommy,"

>Why is the sky blue?

Because it reflects the sea.			(From "Science Made Stupid")

A related joke, due to Feynman: Why do faraway mountains look blue?

Because they're higher up, so gravity is less, so time runs faster, and
thus they're blue-shifted.
								Allen K.
From: phillies@wpi.WPI.EDU (George D. Phillies)
Newsgroups: sci.physics
Subject: scientific literature
Date: 26 Jul 92 19:23:48 GMT
Article-I.D.: wpi.1992Jul26.192348.19076
Distribution: na
Organization: Worcester Polytechnic Institute

In the recent flamefest about hydrogen powered automobiles,
several people appeared to be claiming that Scientific American
is a part of the scientific literature.  This point of view
is basically not defensible.  The journal in question does not
use footnotes and does not as a rule run articles disputing the
points of view of previous articles.  Furthermore, it has been 
for many years visible that its articles on some topics appeared 
to share a common set of political biases (a problem shared by
its university press counterpart Technology Review), so in my 
personal opinion its value as a source of information is open to 
some question. 

Under the orthodox definition of a scientific journal, as one whose 
articles are documented in a scholarly way and whose pages are 
generally open to debate, Scientific American (no matter its 
extensive merits as a refined match to Popular Mechanics) is not a 
scientific journal, and publication in its (undoubtedly culturally 
valuable) pages should not be described as publication in the 
scientific literature.  

George Phillies
phillies@wpi.wpi.edu
From: ethan@ut-emx.uucp (Ethan Tecumseh Vishniac)
Newsgroups: sci.physics
Subject: Re: Defining Photons
Summary: what does particle connote anyhow?
Keywords: Relating photons E=MC^2 criticism
Date: 29 Jul 92 14:28:29 GMT
Organization: The University of Texas at Austin, Austin, Texas


In physics `particle' implies discreteness and, in some
sense, locality.  It does not imply mass.  Having energy
does not imply having mass.  This does not introduce any
mathematical contradictions.  QED does involve some complications
that have to do with the fact that the photon has no mass, but
these complications have well understood solutions. It is 
unfortunate if using the word particle causes some nonphysicists
to assume that mass is involved, but inventing a new word would
lead to greater confusion.

It is remarkable to me what some people imagine are issues in physics.
-- 
"Quis tamen tale studium, quo ad primam omnium rerum causam evehimur,
tamquam inutile aut contemnendum detractare ac deprimere ausit?"-Bridel
Ethan T. Vishniac, Dept. of Astronomy, The University of Texas at Austin
Austin, Texas, 78712                   ethan@astro.as.utexas.edu
From: jcr@milton.u.washington.edu (Mr. EuStress)
Newsgroups: sci.physics
Subject: What is (1/6)M(V^3)?
Date: 22 Jul 92 20:24:42 GMT
Article-I.D.: u.1992Jul22.202442.29505
Reply-To: jcr@milton.u.washington.edu (Mr. EuStress)
Organization: University of Washington


  If momentum is MV (Mass times Velocity) and energy is 
  (1/2)M(V^2) (the integral of MV) what is (1/6)M(V^3)?
    If time is the forth dimension then is time squared
  (acceleration) the fifth dimension?
  Is there any limit to the number of dimensions (degrees 
  of freedom) that we live in?
Newsgroups: sci.physics
From: crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass)
Subject: Re: "What's New" July-24-1992
Organization: University of Virginia
Date: Tue, 28 Jul 1992 23:56:39 GMT

In article <76710@ut-emx.uucp> ethan@ut-emx.uucp (Ethan Tecumseh Vishniac) writes:
>
>>>	WHAT'S NEW, Friday, 24 July 1992                   Washington, DC
>>>
>>>	1. PHYSICISTS IN EUROPE, JAPAN AND CANADA OPPOSE SPACE STATION!
>
>>>	3. SENATE COMMITTEE RESTORES $550M TO THE SUPERCOLLIDER IN FY 93!
>
>>     Is this from the "It may be pork, but its OUR pork" file?
>
>>                                   dale bass
>
>Give me a break.  This falls under the heading of `at least it's science'.
>
>Besides, I would have written it up in almost the same way, and I think
>that the SSC is overpriced.
>
>Haven't we just about beaten this one to death?

     Give me a break.

     Why is the APS vehemently against SSF?  If we ignore possible
     selfish funding considerations, the stated objection is that
     it 'is not science'.  Well, there will certainly be science
     done on the space station.  So the objection boils down to
     'it is too much money for so little science'.

     I rest my case.

                             dale bass

     P.S. I don't see APS officers testifying before Congress about
     chiropractors or astrology, or the NIH funding studies of homeopathy
     or even objecting to SSC supporters selling their project on the
     basis of the engineering advances in cryomagnets.  I wonder
     why the 'sanctity' of science is not of overwhelming importance
     in these cases?
--
C. R. Bass                                           crb7q@virginia.edu
Department of Mechanical and Aerospace Engineering
University of Virginia
Charlottesville, Virginia                            (804) 924-7926
From: sxb@fermi.cray.com (Stephen Behling)
Newsgroups: sci.physics
Subject: What is ESRF?
Date: 30 Jul 92 19:02:17 GMT
Reply-To: sxb@fermi.cray.com (Stephen Behling)
Organization: Cray Research, Inc.



  I have been asked about a European project with the
initials ESRF.  I have no idea.  Can someone help?

  This was asked in a query along with the APS (Advanced Photon
Source) at Argonne--so I guess there's a common thread.

   Thanks...

      Steve Behling    sxb@cray.com