HDTenEightyP/NetNews huggingface dataset:
From: jbaez@riesz.mit.edu (John C. Baez)
Subject: Re: Blue Sky
Organization: MIT Department of Mathematics, Cambridge, MA
Date: Wed, 22 Jul 92 14:57:23 GMT

In article <BrrMJB.Brv@acsu.buffalo.edu> mjb@acsu.buffalo.edu (Matthew J. Bernhardt) writes:
>andrew@rentec.com (Andrew Mullhaupt) writes:
>
>>Why is the sky blue?
>
>	I'll bite.  The composition of the Earth's atmosphere (four fifths
>nitrogen, one fifth oxygen) is such that incoming light is refracted to make
>the sky appear blue.

As far as I know, refraction has nothing to do with it.  Rather, blue
light is scattered.  In physics I recall learning how a free charged
particle is more apt to scatter light of higher frequencies, and this
was claimed to be the explanation for why the sky is blue.  Later I
vaguely recall someone  saying that this was a misleadingly
oversimplified account.  If anyone REALLY knows this stuff I'd be glad
to hear it.  

I've always wondered why there are so few blue animals.  I am also
reminded of George Carlin's routine beginning "There is no blue food!"
Xref: sparky sci.physics:12100 sci.astro:8525 sci.philosophy.tech:2918 talk.religion.misc:13107
From: murphy@npri6.npri.com (David P. Murphy)
Newsgroups: sci.physics,sci.astro,sci.philosophy.tech,talk.religion.misc
Subject: Re: Structure of Time
Date: 30 Jul 92 16:50:43 GMT
Distribution: world
Organization: NPRI, Alexandria VA



>>   These "inquisitors" have contacted to my employer and they have tried
>>to insult me and my paper. My employment is in danger at the moment.
>>
>>hporopudas@tnclus.tele.nokia.fi

 >I'm sorry to see that. We expect a certain type of open 
 >discussion on a newsgroup. The biggest problem to reading something 
 >that is of no interest is either pressing the spacebar or the "n" key.
 >The fact that certain people contacted your employer to complain about 
 >a minor issue like this speaks more of their problem than anything else.
 >
 >psyrobtw@ubvmsb.cc.buffalo.edu (Robert Weiss)

oh, i agree with you, robert.  however, given the quality of his previous
postings, i have a hard time believing that _anyone_ has contacted his
employer.  it could happen, but i doubt it.

besides, he's given me inspiration for a new name in my /etc/passwd entry:
        David "Space Potato" Murphy
has a nice ring to it.  gotta talk to my sysadmin about this.

ok
dpm
-- 
murphy@npri6.npri.com 602 Cameron St. Alexandria, VA 22314 (703) 683-9090

              When every one is dead the Great Game is finished.  Not before.
                              --- Hurree Babu, "Kim"
Newsgroups: sci.physics
From: chaloux@mandolin.mitre.org (Dave Chaloux)
Subject: Re: Structure of Time
Reply-To: chaloux@mandolin.mitre.org (Dave Chaloux)
Organization: The MITRE Corporation, McLean, Va
Date: Wed, 29 Jul 1992 18:01:44 GMT

Yaron Sheffer writes:

>This one's easy: Truth is measureable in the lab, or observable in the
>Universe, and in any case should be consistent and causal with anything
>that we have ever observed/measured in the physical cosmos, whether
>macroscopically or microscopically, preferably both.

I was under the very definite impression that mathematicians have shown that
the number of true statements is a larger order of infinity than the number of
proofs and that therefore there are true statements that cannot be proved.

If I am wrong, I'm sure this will be pointed out 8), but if true this should
make one think twice about statements like the above.
Newsgroups: sci.physics,sci.math
From: jtwamley@physics.adelaide.edu.au (Jason Twamley)
Newsgroups: sci.physics
Subject: Re: Quantum Cosmological Boundaries and Determinisim?
Keywords: Quantum cosmology
Date: 23 Jul 92 10:36:22 GMT

braham@physics.ubc.ca (Stephen Braham) writes:

>shouldn't be confused with the _dynamical_ collapse of the
>wavefunction, induced by decoherence processes- that's a statement
>on a Shroedinger picture density matrix, and ADH is a lot more
>general than that.
                                          ^^^^^^^^^^^^^^^^^^^^^^

Hmmmm... I have head it said that ADH may be too restrictive for any
system to match up to the Gell-Mann Hartle (GMH) criterion of quai-classical.
Even Omnes believes that the GMH decoherence criterion is too tough...
It must be checked in some actuall models.. Halliwell and Dowker 
(FERMILAB-PUB-92-44-A, CTP # 2071) have
ploughed through some awfull calculations for a very simple system of
a free particle coupled to a thermal bath (the Caldeira-Leggett model)
and have found that the histories do not decohere (ala ADH) completely
but to the extent that they do they seem to be peaked around the
classical paths in (x,p) phase space. But this is perhaps one of the
simplest models one can have and also there are still ambiguties
concerning how does one quantify how good the decoherence is, the
concept of peaking about the classical path, etc. How model dependent
are the results? Another model using ADH with inflation shows no
decoherence  whatsoever (in preperation). Harmonic oscillators, while
the testbed for many theories, possess many special properties not
found in even slightly more complicated models. 

Jason
Xref: sparky sci.physics:11847 sci.astro:8414 sci.philosophy.tech:2886 talk.religion.misc:12843
From: sichase@csa2.lbl.gov (SCOTT I CHASE)
Newsgroups: sci.physics,sci.astro,sci.philosophy.tech,talk.religion.misc
Subject: Re: Structure of Time
Date: 28 Jul 92 19:39:02 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 <1992Jul28.175239.10109@hpcvaac.cv.hp.com>, billn@hpcvaac.cv.hp.com (bill nelson) writes...
> 
>I can't say I am sorry for you. It would be nice of you restricted you
>postings to alt.paranormal or alt.kids.with.imaginations.and.gullible.
>parents or alt.overimaginative.parents.  
> 
>What you have posted does not even begin to follow what is called the 
>scientific method. Physicists love the truth, but random babbling is
>not truth.
> 
>You were asked a number of times to take your postings somewhere else
>where they would be appreciated. You ignored the requests - you deserve
>to suffer the consequences - whatever they may be.

Yow!  That's a little harsh, don't you think?  Plenty of folks, sometimes
even intentionally, post nonsense to this group.  I probably do it now
and then by mistake.  I don't think his job should be at risk because
he chooses to interact with us in the only way he knows how.  

I wonder what someone could have said to his employer, that if he
was otherwise satisfied with his performance could have put his job
in jeopardy?



--------------------
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
From: mcirvin@husc8.harvard.edu (Mcirvin)
Newsgroups: sci.physics
Subject: Re: Structure of Time
Date: 29 Jul 92 00:35:38 GMT
Distribution: na

sichase@csa2.lbl.gov (SCOTT I CHASE) writes:
>In article <1992Jul28.175239.10109@hpcvaac.cv.hp.com>, billn@hpcvaac.cv.hp.com (bill nelson) writes...
>>[some stuff deleted] 
>>What you have posted does not even begin to follow what is called the 
>>scientific method. Physicists love the truth, but random babbling is
>>not truth.
>>[some more stuff deleted] 
>Yow!  That's a little harsh, don't you think?  Plenty of folks, sometimes
>even intentionally, post nonsense to this group.  I probably do it now
>and then by mistake.  I don't think his job should be at risk because
>he chooses to interact with us in the only way he knows how.  

Also, there are many theorists like me in this group, and I'm
not sure that anything we say could be construed as "scientific
method," let alone "truth."  We don't obtain our information from
small children, but we don't check our musings by building
experiments either... that's someone else's job.

Inappropriate postings will abound in any unmoderated group.
So will mistakes, hallucinations, massive crossposts, etcetera.
I'd hate to have my erroneous babbling about supersymmetry on
this group when I was a rank newbie brought up as evidence in my
qualifying oral exam.

Our best defense is to swamp the noise with signal.

-- 
Matt McIrvin  mcirvin@husc.harvard.edu 
Newsgroups: sci.physics
From: gl8f@fermi.clas.Virginia.EDU (Greg Lindahl)
Subject: Re: ZERO Nuclear impact (was: Is car pooling for real? etc)
Organization: Department of Astronomy, University of Virginia
Date: Sat, 25 Jul 1992 05:54:21 GMT

In article <1992Jul24.221351.10050@Princeton.EDU> mdd@nextc.princeton.edu writes:

>No one seems to have mentioned this yet...There are other ways to  
>distribute solar power besides using an electrical grid. Solar power can  
>be used to convert water to hydrogen quite efficiently and the hydrogen  
>could then be transported through an infrastructure similar to the natural  
>gas infrastructure that already exists.

Actually this was discussed in the 9-90 Scientific American issue, and
there also have been several earlier articles in Scientific American
on topics of this sort.
From: jmp1@ns1.cc.lehigh.edu (JEFFREY MICHAEL PARSONS)
Newsgroups: sci.physics
Subject: Re: Destroying the Earth
Date: 28 Jul 92 16:04:18 GMT
Organization: Lehigh University

In article <1992Jul28.044315.24255@nuscc.nus.sg>, matmcinn@nuscc.nus.sg (Mcinnes
 B T (Dr)) writes:
>To what radius would we have to compress the Earth in order to form a
>black hole? The Schwarzschild radius is usually cited, but that is
>rather strange, because the Schwarzschild radial coordinate does not
>measure distance.
>
I understand that setting escape velocity to c in the classical escape
velocity equation gives the radius of the event horizon of a black hole with
said mass.  If you could compress the Earth to that radius, you would be all
set. :-)

Jeff Parsons
Lehigh University
Physics Undergrad
-- 
Newsgroups: sci.physics,alt.fan.dale-bass
From: gsh7w@fermi.clas.Virginia.EDU (Greg Hennessy)
Subject: Re: "What's New" July-24-1992
Followup-To: alt.fan.dale-bass
Organization: University of Virginia
Date: Wed, 29 Jul 1992 03:06:15 GMT

In article <1992Jul29.024403.5319@murdoch.acc.Virginia.EDU>
crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass) writes: 
#     Yes 'forced'.  Meaning that they were made to do something that
#     they would rather not, for good and obvious reasons.

And what are these good and obvious reasons, pray tell? 

#     The position of the APS is that the space station is not 'science'
#     and should not be funded as such.   I would just expect them to pursue 
#     other 'science purity' issues with the same vigour.

They do pursue such purity with all such multi-billion dollar projects
in the budget. Oh, what's that? Astrology isn't funded by the US
government? Damn, there goes your arguement. 

#     So it is competition for dollars with other programs of more
#     direct interest to APS rather than the 'science-thing'?  I'm 
#     shocked.

Well, you created this strawman, so it isn't suprizing that you are
shocked by it. However, since I never claimed it was solely the
competition for dollars, you lose. Judging the bang per buck of a
project certainly is a valid thing to do for the APS.

#     Agreed.  However, it is disingenuous to say that it is any different
#     for SSC.  By the way, the hypocracy of the APS with regard to 
#     SSF and SSC was the original subject.  It still exists.

Oh, the fact that the APS and you draw different conclusions about the
scientific merit of the SSC makes them hypocrites?

The APS has reached the conclusion that the scientific gains of the
SSC are large, and it has a good ratio of science to cost, so they
support it.

The APS has reached the conclusion that the scientific gains of the
SSF are minimal, and it has a poor ratio of science to cost, so they
oppose it.

Refresh my memory, would you Dale, on why this arguement is
hypocritical? 


--
-Greg Hennessy, University of Virginia
 USPS Mail:     Astronomy Department, Charlottesville, VA 22903-2475 USA
 Internet:      gsh7w@virginia.edu  
 UUCP:		...!uunet!virginia!gsh7w
From: andrew@rentec.com (Andrew Mullhaupt)
Newsgroups: sci.physics
Subject: Re: Blue Sky
Date: 24 Jul 92 13:49:36 GMT
Organization: Renaissance Technologies Corp., Setauket, NY.

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:
>> 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

Some carnivorous birds have adopted this strategy - penguins. However the
important factor which hawks and other raptors do not have in common with
penguins is that penguins are subject to in-flight predation. (The word flight
can be applied here in the best fluid dynamic tradition.) Now many land based
predators use camouflage - (polar bears, tigers, etc.) - and owls use important
flight silencing techniques. So I don't know why raptors don't seem to have
such a strategy.

Later,
Andrew Mullhaupt

Newsgroups: sci.physics
From: dexter@news.mr.med.ge.com.UUCP (Donald Dexter 4-6489)
Subject: Re: Structure of Time (SUMMARY)
Organization: GE Medical Systems, Magnetic Resonance
Distribution: na
Date: Fri, 24 Jul 92 17:11:01 GMT

From article <24824@dog.ee.lbl.gov>, by sichase@csa2.lbl.gov (SCOTT I CHASE):
> In article <499@alden.UUCP>, sgr@ae-sun05 (Stan Ryckman) writes...
>> 
>>If _anything_ has a color, it does one or more of:
>>   a) emit optical photons;
>>   b) reflect optical photons;
>>   c) absorb optical photons; or
>>   d) refract optical photons.
>> 
>>No neutrino ever has been hypothesized by any physicist to interact
>>with photons in any such way.  If so, they'd be easy to detect.
> 
> Whoa!  Neutrinos most definitely can interact with photons of any
> wavelength.  After all, neutrinos have a magnetic moment (very small,
> not yet measured, upper limits only known so far) in the Standard
> Model.  Think of it this way - every neutrino spends part of its life
> looking alot like a W-lepton pair. 
> 
> And photons get involved in weak interactions through trilinear and 
> quadrilinear boson verticies, so even in first order some unfamiliar
> processes can lead to neutrino-photon interactions.  For example,
> neutrino + photon -> lepton + W* + photon -> lepton + W.
>
yea, but are they green?   :-)

-don.      (neutrinos are the little green things)
From: love@geophysics.harvard.edu (Jeff Love)
Newsgroups: sci.physics
Subject: Re: Blue Sky
Date: 27 Jul 92 22:49:15 GMT
Article-I.D.: das.1992Jul27.224915.15755
Reply-To: love@geophysics.harvard.edu
Organization: Dept. of Earth & Planetary Sciences, Harvard University

In article 6472@ruhets.rutgers.edu, bweiner@ruhets.rutgers.edu (Benjamin Weiner) writes:
>Jeff Love writes:
>>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.
>
>Have you actually tried reading Jackson's explanation?  As a hint,
>Jackson's title is _Classical Electrodynamics_.  More to the point,
>if _Rayleigh_ got it right in 1871 there must indeed be a classical
>explanation, namely Rayleigh's.  [Rayleigh, Phil Mag XLI, 107, 274,
>(1871), and Phil Mag XLVII, 375 (1899), refs cribbed from Jackson]
>Basically the assumptions that go into the explanation are that
>molecules have predominantly electric dipole polarizability, and 
>that they are small compared to the wavelength of the light.
>Incidentally, I believe that da Vinci understood that blue light
>was scattered preferentially, causing the blue sky, but didn't know
>why.  (He certainly didn't derive a k^4 dependence).  I don't think
>one can claim that his argument is based on "classical physics" in
>the usual sense.
>
>BTW, to Al Kriman: Perhaps if prophecies of the decline of atmospheric
>ozone are true, we will eventually see a more violet sky.
>
>Ben Weiner
>
>I don't think of myself as a classical physicist, rather a
>twelve-tone physicist.


Wow. Okay, maybe I didn't read Jackson's book before I posted my question. 
I guess what I was hoping for was a heuristic arguement as to why blue light
is scattered whilst red light is not (at least not as much), or maybe a simple
dimensional arguement could yield the k^4 dependence; I admit that I haven't
tried to put one together. I see that the stuff in Jackson regarding Blue
Sky is classical, so I misspoke. But not all of Jackson is classical, despite
the title ( hbar does appear a times ). I was hoping for a qualitative
or semiquantitative explanation, not a rigorous explanation.

The "explanation [is] that molecules have predominantly 
electric dipole polarizability, and  that they are small compared to 
the wavelength of the light" doesn't really help me. I suppose I could
go do some research and learn the answer that way, but I thought I'd
use the net instead.

Jeff Love
Organization: Johannes Kepler University Linz - Computing Center
Date: Wednesday, 22 Jul 1992 13:29:33 CDT
From: <K31412I@ALIJKU11.BITNET>
Newsgroups: sci.physics
Subject:    Physics in Portugal

I'm going to Portugal, possibly also Spain and France via Interrail on
the 1st of August and should also like to visit anything worth seeing
as far as Physics is concerned in these countries|
Who can give me a hint on what there is where, and it would also be nice
if people knew, how one can get into those places|
I should be grateful for any little idea, no matter, of what kind||
(By the way: Any other insider-tips on lovely places to go in Portugal?)

Thank you very much, Suzanne Schuster (K31412i at alijku11.edvz.uni-linz.ac.at)
Newsgroups: sci.physics
From: silverstein@vxdesy.desy.de
Subject: Jacob's Ladder (WAS Re: What are those things called...)
Organization: (DESY, Hamburg, Germany)
Date: Sun, 26 Jul 1992 21:55:32 GMT

In article <Bs0D4v.466@helios.physics.utoronto.ca>, jamesm@helios.physics.utoronto.ca (James Mihaychuk) writes:
> In article <1992Jul23.214214.8574@microplex.com> hsk@microplex.com (Harjeet Kalsi) writes:
>>I know I've seen them in physics labs (including mine when I was in school) 
>>but forgotten what this "box" with two antennas, that has a high
>>voltage spark travelling between the antennas from bottom to top,
>>is called.
>>
>>hsk@microplex.com
> 
> My high school physics teacher told me it was called a Jacob's Ladder, although
> there might be other names.
> ---
> James Mihaychuk, indentured servant  You say your moon's in the seventh house,
> (lowly physics grad student)         But your butt spent three days on my couch
> jamesm@helios.physics.utoronto.ca    "Eternal Fatalist," the Lowest of the Low 

Yeah, that's what I've always heard it called. Now, here's a puzzler for
you. The two "antennae" are closer together at the bottom than at the top, 
and the spark starts at the bottom and travels upwards. Now, a spark prefers to
"jump" the shortest gap between two conductors. So why does the spark move up? 
(Let's see how many people REALLY listened to their high school instructor :-)

Sam Silverstein
UW-Madison Department of Physics
From: John.Matylonek@bbs.oit.unc.edu (John Matylonek)
Newsgroups: sci.physics
Subject: mass of quarks?
Keywords: quark property
Date: 29 Jul 92 13:09:25 GMT
Distribution: usa
Organization: Extended Bulletin Board Service

has anyone yet determined the mass of a quark?	

Matylojc at duvm.ocs.drexel.edu




--
   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
From: matt@physics2.berkeley.edu (Matt Austern)
Newsgroups: sci.physics
Subject: Re: Blue Sky
Date: 21 Jul 92 23:17:27 GMT
Reply-To: matt@physics.berkeley.edu
Organization: Lawrence Berkeley Laboratory (Theoretical Physics Group)
NNTP-Posting-Host: physics2.berkeley.edu
In-reply-to: mjb@acsu.buffalo.edu's message of 22 Jul 92 00:54:47 GMT

In article <BrrMJB.Brv@acsu.buffalo.edu> mjb@acsu.buffalo.edu (Matthew J. Bernhardt) writes:

> >Why is the sky blue?

> 	No doubt the quantum mechanical justification of this phenomenon
> is forthcoming...

No quantum mechanical explanation is necessary; there is a perfectly
good classical explanation in section 9.7 of Jackson.  (Jackson,
incidentally, points out that the physical explanation of why the sky
is blue was understood by Leonardo da Vinci, in 1500 or so.)

Summary: the scattering of light by nitrogen molecules is higher for
higher-frequency light.  So the light that we see in the sky, which is
entirely scattered sunlight, is predominantly blue and violet
frequencies.  For the same reason, sunsets are red.
--
Matthew Austern              I dreamt I was being followed by a roving band of
(510) 644-2618               of young Republicans, all wearing the same suit,
matt@physics.berkeley.edu    taunting me and shouting, "Politically correct
austern@theorm.lbl.gov       multiculturist scum!"... They were going to make
austern@lbl.bitnet	     me kiss Jesse Helms's picture when I woke up.
Xref: sparky sci.physics:11873 sci.astro:8422 sci.philosophy.tech:2889 talk.religion.misc:12876
From: st0o+@andrew.cmu.edu (Steven Timm)
Newsgroups: sci.physics,sci.astro,sci.philosophy.tech,talk.religion.misc
Subject: Re: Structure of Time
Date: 28 Jul 92 12:06:21 GMT
Organization: Doctoral student, Physics, Carnegie Mellon, Pittsburgh, PA

Could it be that the reason fewer young ladies are interested in 
physics and cosmology nowadays is because they receive such rough
treatment at the hands of know-it-all netters?  It seems to me that for
a little 
girl of 5 years old to even know about neutrinos and radiation and
electricity  is quite a bit to ask.

After all , it was only ten years ago or less that the rage in cosmology 
was to dream up new particles and determine what effect they might 
have on the universe.  Why not the space potato?  It's no more exotic
than many particles which well-known theorists have published papers on, and 
are no more likely to exist than the space potato.

Steve Timm
Newsgroups: sci.physics
From: dwr2560@zeus.tamu.edu (RING, DAVID WAYNE)
Subject: Re: ... an infinite mesh of 1ohm resistors ...
News-Software: VAX/VMS VNEWS 1.41    
Organization: Texas A&M University, Academic Computing Services
Date: Thu, 30 Jul 1992 19:53:00 GMT

ttyytt@mixcom.com (Adam Costello) writes...
>The original "solution" went something like this:  Imagine connecting a
>one amp current source between A and B.  Now split this image into two
>separate cases which we will later superimpose.  In one case, the current
>goes in to terminal A, but doesn't come out anywhere.  In the other case,
>the current comes out terminal B, but doesn't go in anywhere.  I doubt
>you ever did anything like this in EE 101.  (I sure didn't!)

But it's not hard to set it up. Rub a glass rod to a piece of wool. Touch
it to a grounded circuit. If you have enough wool and can repeat quickly
enough you can put one amp into the circuit (which for our purposes includes
the entire 'ground'). :-)

Dave Ring
dwr2560@zeus.tamu.edu