HDTenEightyP/NetNews huggingface dataset:
From: carl@aoa.aoa.utc.com (Carl Witthoft)
Subject: Re: Blue Sky
Organization: Adaptive Optics Associates
Date: Mon, 27 Jul 1992 18:55:07 GMT

In article <1992Jul23.010953.6388@math.ucla.edu> barry@arnold.math.ucla.edu (Barry Merriman) 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 
>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
x
You should move this thread to sci.military, where you probably can
get some refs to disruptive coloration, dazzle, and other tricks
of camouflage.  The short answer is: objects are made invisible by
matching irradiance, not color, to their background, or by breaking
their natural lines (e.g. bridgework on a ship) up into randomized
patterns.  Many birds such as the killdeer have bright stripes on
their body which helps them disappear into the grass.


-- 
Bobby Newmark, aka  Carl Witthoft @ Adaptive Optics Associates
aoa!carl@bbn.com  carl@aoa.utc.com
54 CambridgePark Drive, Cambridge,MA 02140 617-864-0201
**Just say NO to HMOs**
Newsgroups: sci.physics
From: crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass)
Subject: Re: Blue hawks (was Blue Sky)
Organization: University of Virginia
Date: Wed, 29 Jul 1992 18:04:28 GMT

In article <1128@kepler1.rentec.com> andrew@rentec.com (Andrew Mullhaupt) writes:
>In article <1852@snap> paj@uk.co.gec-mrc (Paul Johnson) writes:
>
>>Active illumination is not an option available to eagles.
>
>Is this obvious? Bioluminesence is at least theoretically possible, and
>the question is can the eagle generate a bright enough light. I can't
>think of bioluminesence which is bright enough but is there any good
>(i.e. theoretical) reason why they can't, (perhaps the color temperature
>of the sky is higher than what room-temperature chemical reactions can
>afford?)
>

     There is probably a severe evolutionary penalty for active illumination.

     In fact, it is my guess that the most inexpensive set would cost many
     tens of thousands of eagle-years labor, imposing large weight and
     aerodynamic penalties, and a whole bunch of standing around waiting
     for radar to be invented...

                                    dale bass




--
C. R. Bass                                           crb7q@virginia.edu
Department of Mechanical and Aerospace Engineering
University of Virginia
Charlottesville, Virginia                            (804) 924-7926
From: clarke@acme.ucf.edu (Thomas Clarke)
Newsgroups: sci.physics
Subject: Re: Twins Paradox Resolved
Date: 30 Jul 92 15:14:51 GMT
Article-I.D.: cs.1992Jul30.151451.12344
Organization: University of Central Florida

In article <Bs64Dz.Hw3@well.sf.ca.us> metares@well.sf.ca.us (Tom Van Flandern)  
writes:
> 
> Earlier, I wrote:
> 
> >> As for logical problems, one must give up totally on the concept of
> >> distant simultaneity; and one must accept that *apparent* aging depends
> >> upon direction of travel, approach or receding.  There is a way to avoid
> >> both of these considerable logical compromises.  But I do not argue that
> >> they cannot be possible, only that one must make a sacrifice
> >> (unnecessarily, it turns out) of "common sense" to accept this
> >> interpretation of the experimental data.
> 
>      Cute, but your point was lost.  What is it that you find impossible to
> believe?
>      a) SR
>      b) the need to give up on distant simultaneity
>      c) that apparent aging depends upon direction of travel
>      d) that other interpretations consistent with the experimental evidence
> are also possible
>      e) something else
> 

I should forget quoting from literature, the ease with which 
I can paste things from the Next Librarian distracts me from the
issues at hand.

Re-thinking about your statement, I realize that I have again
misread you.  My reading is to take b) as a corollary of a).
But I think you seperate the two.  Part of the mother's milk
of relativity is to become suspicious of simultaneity and to
handle any statements including "simultaneity" with kid gloves.

Your use of the word "distant" seems to imply a distinction 
between the cases when the seperation of two events is spacelike 
from when it is timelike; "simultaneity" being an invariant concept
in the former case.  I guess if you assume this, then your
argument leads to your conclusions.  But simultaneity is just
as suspect for spacelike intervals.

I think I am correct in saying that c) is a specific case of d).
I believe I am correct about SR being the unique theory that
makes relativizes Maxwell's equations, ruling out any d) arrived 
at by the style of reasoning your adopt.

Not to say that relativity is the last word, but revolution will
come from another direction.  Perhaps quantum gravity, perhaps
another little noticed chink in physics' armor.   
 

--
Thomas Clarke
Institute for Simulation and Training, University of Central FL
12424 Research Parkway, Suite 300, Orlando, FL 32826
(407)658-5030, FAX: (407)658-5059, clarke@acme.ucf.edu
Newsgroups: sci.physics
From: m14494@mwvm.mitre.org (Mike White)
Subject: Re: Blue Sky
Organization: The MITRE Corporation
Distribution: na
Date: Wed, 22 Jul 1992 15:42:33 GMT

Andrew Mullhaupt writes:
> Why is the sky blue?

You'll get lots and lots of answers, and I'll bet my tenure that not one 
of them will address the question "Why?"; they'll all address the question 
"How?".  They'll go on and on about scattering of light from Nitrogen 
molecules, but the question of "Why?" is much harder.  The mechanism that 
makes the sky blue is well understood, but why does that mechanism exist, 
instead of one that makes the sky, say, green?  This rapidly gets into 
metaphysics; I think the answer has to do with conditions that make it 
possible for us to exist to ask the question in the first place.

************************
* These are my opinions only.*
************************
Newsgroups: sci.physics
From: jmc@SAIL.Stanford.EDU (John McCarthy)
Subject: Re: Low Tech is Best
Reply-To: jmc@cs.Stanford.EDU
Organization: Computer Science Department, Stanford University
Date: 22 Jul 92 20:07:58

What about efficiency in human labor?  Why were all the belt systems
in textile mills replaced by electric motors?  I'll bet it was for
flexibility.
--
John McCarthy, Computer Science Department, Stanford, CA 94305
*
He who refuses to do arithmetic is doomed to talk nonsense.
From: mitsu@nic.cerf.net (Mitsuharu Hadeishi)
Newsgroups: sci.physics
Subject: Re: ***********MIND-BLOWING GEDANKENEXPERIMENT**********
Date: 25 Jul 92 03:09:45 GMT
Organization: CERFnet


In article <92206.164128MRG3@psuvm.psu.edu> MRG3@psuvm.psu.edu writes:
>If this is indeed the proposal from Physics Essays, then I have a few comments:
>That proposal has a fundamental, but subtle flaw, which may remain in this
>proposal.

        Yes, it seems the spin-flip process is the mysterious process
involved here.  Though I'm not sure that is the end of the story.  How
to account for the following set-up, a simple experiment which I came
up with while thinking about the Sarfatti experiment:

       Suppose you had a pair of correlated photons, and you detect
a vertical event at the left detector.  This guarantees, of course,
a vertical event detection on the right detector.  Now, rather than
passing the photon on the right through a birefringent crystal which is
rotated by 45 degrees, but through a crystal with the same orientation,
and you again pass the photon through a half-wave plate and recombine.
A "normal" uncorrelated photon passing through such an apparatus would
split and interfere with itself, and you would expect interference
fringes.  However, if the correlated photon on the left has *already
been detected* as vertically polarized, this means you have to
detect the photon on the right as vertically polarized.  Thus, it
should pass through the birefringent crystal via the V path, and hit
the detector with no interference with itself.  E.g., if you detect
the photon on the left, you would not get interference, if you
don't detect it, you will.  (When I say interference I mean, of course,
statistically speaking).  This apparatus seems to conserve probability
and also allow FTL communication, at least at first glance.  What is
wrong with this picture?  (if there is anything wrong).

Mitsu Hadeishi
General Partner, Open Mind Research
mitsu@cerf.net
mitsu@well.sf.ca.us
From: matt@physics2.berkeley.edu (Matt Austern)
Newsgroups: sci.physics
Subject: Re: "What's New" July-24-1992
Date: 25 Jul 92 13:36:43
Organization: Lawrence Berkeley Laboratory (Theoretical Physics Group)
Reply-To: matt@physics.berkeley.edu
NNTP-Posting-Host: physics2.berkeley.edu
In-reply-to: jmc@SAIL.Stanford.EDU's message of 25 Jul 92 12:39:47

In article <JMC.92Jul25123947@SAIL.Stanford.EDU> jmc@SAIL.Stanford.EDU (John McCarthy) writes:

> My opinion is that the physicists are mistaken about the space
> station, imagining they could get some of the money saved by the
> cancellation.

There may well be some physicists who think this, but most, I think
are more realistic.

For myself, my opposition to the space station is because I would like
to see a healthy space program (and yes, one that includes human
flight, and probably one that includes a space station and a lunar
colony), and it is my opinion that this particular space station is
more likely to be detrimental to this goal than advantageous.  I
believe that it would be better to cut our losses (perhaps with the
shuttle as well), start over, and do it right.

I agree that when people argue that the space station is
scientifically unjustified, they are missing the point: science isn't
the reason why anyone wants to build it.  Still, the government and
the press treats it as a science project: how many stories have you
seen that talk about the space station, the human genome project
(HUGO), and the SSC as the government's major scientific expendatures?
It is worth pointing out that, unlike the SSC and HUGO, the space
station is not a science project, and not something that scientists,
qua scientists, have asked for.
--
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.
From: DOCTORJ@SLACVM.SLAC.STANFORD.EDU (Jon J Thaler)
Newsgroups: sci.physics
Subject: Preprint bulletin boards (was: GR/QC mailing list)
Date: 31 Jul 92 15:35:59 GMT
Organization: Stanford Linear Accelerator Center

baez@ucrmath.ucr.edu (john baez) says:

> There is now a preprint mailing list for the above subjects.
> Send a message to gr-qc@xxx.lanl.gov with header HELP and no
> message body for information.

For those who are interested, here are some other bulletin boards running
the same software.  The above procedure will work with any of them.

alg-geom@publications.math.duke.edu (algebraic geometry)
astro-ph@babbage.sissa.it           (astrophysics)
cond-mat@babbage.sissa.it           (condensed matter)
funct-an@babbage.sissa.it           (functional analysis)
hep-lat@ftp.scri.fsu.edu            (computational and lattice physics)
hep-ph@xxx.lanl.gov                 (high energy physics phenomenological)
hep-th@xxx.lanl.gov                 (high energy physics formal)
lc-om@alcom-p.cwru.edu              (liquid crystals, optical materials)
Newsgroups: sci.physics
From: dc@stars.gsfc.nasa.gov (Dave Cottingham)
Subject: Space Station & APS
Summary:  Building an interplanetary bureaucracy
News-Software: VAX/VMS VNEWS 1.4-b1  
Keywords:  infrastructure infrastructure infrastructure
Reply-To: dc@cobi.gsfc.nasa.gov
Organization: NASA/GSFC-Laboratory for Astronomy and Solar Physics
Date: Wed, 29 Jul 1992 17:17:00 GMT

There has been an active flame war here on the recent APS statement
on the proposed Space Station, which I want to jump into right here.

I have seen statements flying by that the APS opposes the Space Station.
However, if you read the statement you can see that the APS only opposes
the justification of SSF on the grounds of scientific research.
Basically, the supporters of SSF told the public "This will be great for
science" and the scientists have responded "It won't either".  The APS
does not comment on other purported justifications of the SSF.

Nor does the APS claim that no science will be done on the Space Station.
Indeed, we only have to look at the history of the shuttle to forsee
the future of space station science.  Experiments that would be better
and more cheaply done in rocket-launched satellites will be forced to
take a ride on the shuttle and get bolted to the Space Station.

 - Dave Cottingham
   dc@cobi.gsfc.nasa.gov
   Disclaimer: My opinions, not necessarily those of USRA,
               and obviously not those of NASA.
Xref: sparky sci.physics:11298 sci.astro:8203 sci.space:10613 sci.edu:890
From: danmac@maxwell.physics.purdue.edu (Daniel L. MacIsaac)
Newsgroups: sci.physics,sci.astro,sci.space,sci.edu
Subject: Compiling a list of Internet/BITNET Physics Education resources
Keywords: Physics instruction, electronic networking
Date: 21 Jul 92 21:44:54 GMT
Followup-To: sci.physics
Organization: Purdue University Physics Department

[descriptions of physhare, phys-l, tap-l, chemed-l, Spacelink, SpaceMet,
Newton deleted for brevity]

Thanks, Dave!

...maybe it is a trivial task to assemble an annotated bibliography on such
resources via email (if you will permit me the bandwidth).  I would LOVE to
edit together and repost/redistribute such an annotated bibliography if others
are willing to provide material for it.

***HERE IS THE PUNCHLINE***

If YOU have or know of a Physics education related resource available via
the internet or bitnet (such as textfiles, databases, BBS, listserv, news-
groups, telnet sites etc), please send its name, complete access/joining info
and a short (1-3 line) description to me.  (see examples appended)

I will assemble a 2 or 3 page catalogue and repost it.  After it has
settled somewhat, I will determine some method of achiving it so it is
accessible to all Bitnet and Internet users, and I will update it periodic-
ally with new information as it is made available to me.   I can cope with
being an archivist in the interest of remaining current on the topic of
physics education/the internet.

ADVthanksANCE

Dan

[Physics] '...is a narrow and rigid education, probably more so than any other
except perhaps in orthodox theology'
                        --  T.S. Kuhn, The Structure of Scientific Revolutions
Dan MacIsaac, Science Ed/Physics Grad Student, danmac@physics.purdue.edu

Examples:

> Listserves
>
> physhare
> subscribe at listserv@psuvm
> sharing resources for high school physics teachers
>
> phys-l
> subscribe at listserv@uwf
> college physics teachers with some K-12 participation
>
> tap-l
> subscribe at mailserv@appstate
> questions about physics, lab equipment - welcome K-12 questions

Catalogue so far (21 July 92):

physhare, phys-l, tap-l, chemed-l, Spacelink, SpaceMet, Newton 


[Physics] '...is a narrow and rigid education, probably more so than any other
except perhaps in orthodox theology'
                        --  T.S. Kuhn, The Structure of Scientific Revolutions
From: yergeau@cornu.phy.ulaval.ca (Francois Yergeau)
Newsgroups: sci.physics
Subject: Re: Blue Sky
Date: 28 Jul 92 15:34:03 GMT
Organization: Universite Laval, Quebec

In article <1992Jul27.224915.15755@das.harvard.edu> love@geophysics.harvard.edu  (Jeff Love) writes:
>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.

In his book "Optics", K.D. Moller offers just such an argument, but it
requires that you admit a couple of things that only further study will
prove (one may try Jackson).  Here goes:

We have a polarizable body of index n2, imbedded in a medium of index
n1.  A wave impinges on the body, inducing forced dipole oscillations
in it.  Said dipole oscillations will in turn re-radiate an outgoing
wave, whose amplitude will be inversely proportional to the distance
from the body.  Let's try to build an expression for the outgoing
intensity, using dimensional analysis:

  I
  - = f(r,V,lambda,n1,n2,theta,phi)
  I0

where r is the distance from the scattering body, theta and phi denote
the direction, V is the volume of the scattering body and lambda the
wavelength.  n1, n2, theta and phi fall out of the analysis, being
dimensionless.  Now if we assume that the _amplitude_ of the dipole
radiation is proportional to the volume of the body and inversely
proportional to the distance, the _intensity_ will be proportional to
V^2/r^2, or length^4; we must then have a lambda^-4 dependance to
balance the units.

QED, though not that convincing.

BTW, the often quoted requirement that the body must be much smaller
than lambda is implicit in the assumption that the radiated amplitude
is proportional to V.  If the body is too big, dipole radiation from
different parts of it will be out of phase and cancel out, and the
total amplitude will not grow as V anymore.
-- 
Francois Yergeau (yergeau@phy.ulaval.ca) |  Quand le doigt montre la lune,
Centre d'Optique, Photonique et Laser    |  l'imbecile regarde le doigt.
Departement de Physique                  |               -proverbe chinois
Universite Laval, Ste-Foy, QC, Canada    |
Newsgroups: sci.physics
From: crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass)
Subject: Re: ZERO Nuclear impact (was: Is car pooling for real? etc)
Organization: University of Virginia
Date: Sat, 25 Jul 1992 17:28:32 GMT

In article <1992Jul25.171557.4574@murdoch.acc.Virginia.EDU> crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass) writes:
>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. End users would then burn the  
>>hydrogen. Or even better use it to power fuel cells. It is likely (I am no  
>>expert) that is a more cost effective approach to solar energy than  
>>erecting solar panels on the East coast, say. 
>
>     Only two big problems.  1) It is not economical to do so,
>     2)  Hydrogen go boom.
>
>     [stuff deleted]

      I further expound upon this succinct and witty response (saying 
      so myself).  Economics are always left out of the
      discussion.  If it is 'economical' to do this with solar, it
      would be even cheaper to do this with coal or nuclear.  Once
      you see this, you see why it is silly to propose changing the energy 
      distribution infrastructure based on a gut feeling that 
      solar is somehow 'better'.

      Of course, this argument usually comes from people who do not
      believe that nuclear plants are pretty benign.

                                 dale bass
--
C. R. Bass                                           crb7q@virginia.edu
Department of Mechanical and Aerospace Engineering
University of Virginia
Charlottesville, Virginia                            (804) 924-7926
From: alexa@hpnmdla.sr.hp.com (Alexander Anger)
Date: Thu, 23 Jul 1992 22:28:39 GMT
Subject: Re: Blue Sky
Organization: Hewlett-Packard, Santa Rosa, CA
Newsgroups: sci.physics

>In sci.physics, andrew@rentec.com (Andrew Mullhaupt) writes:
>
>    Why is the sky blue?


I'm not a physicist, but I am aware of the traditional Rayleigh scattering
theory.  My question to the experimentalists out there is the following:

Has anybody ever checked on the quantitative contribution to the blue
color in the sky due to the effect of ozone?  My CRC tells me that ozone
is a bluish gas, and you'd think that just as with a bluish lens, the 
light coming through would be slightly blue, so a bluish gas would make
the light coming through slightly blue, wouldn't it?  Of course, the key
is the amount contributed by scattering versus the amount contributed
by ozone.  Since the ozone layer is so thin, maybe its effect on the
blue sky is completely negligible (8 orders of magnitude down maybe).
But it would be kind of fun if ozone actually played a more important
quantitative factor.  I'm afraid I don't have time to pursue this question,
but if anyone else has ever heard or thought of this hypothesis, how
about replying?

Thanks,

Alexander Anger
From: rsf1@RA.MSSTATE.EDU (Robert S. Fritzius)
Newsgroups: sci.physics
Subject: Re: Relativity
Date: 25 Jul 92 18:18:50 GMT

Oops!
 
In article <9207251756.AA07822@Ra.MsState.Edu> I said:
 
In article <1992Jul22.150401.15820@news.endg.convex.com> Steve Warren
writes:
 
> [See text below.]
 
That should have been:
 
In article <14pn2cINNhsv@agate.berkeley.edu> emarkp@ocf.berkeley.edu
E. Mark Ping writes:
 
>. . .
>...When particles get zinging around near c in, say, the Bevatron
>here at Berkeley, not only does it require more enery to accelertate
>them, but when they smash into something (...) the energy released
>is significantly *more* than can be accounted for by the particles
>rest mass...
 
Sorry for the mixup.
 
--------------------------------------------------------------------------
 
 
             Robert S. (Bob) Fritzius  rsf1@ra.msstate.edu
                   I have a slobber-proof keyboard!
      Low-Tec  P.O. Box 1327 Starkville, MS 39759   (601) 324-1284
From: crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass)
Newsgroups: sci.physics
Subject: Re: Space Station & APS
Date: 31 Jul 92 00:47:44 GMT
Organization: University of Virginia

In article <1992Jul30.214339.38024@ns1.cc.lehigh.edu> jmp1@ns1.cc.lehigh.edu (JEFFREY MICHAEL PARSONS) writes:
>Can anyone confirm what Sen. Grahm (Texas) said on CBS This Morning (7/30/92)?
>I believe that he said that governmental funding of science research has gone
>from a former (stable) 5% of the budget to 1.8% (1.6% without the SSC) under
>the current Congress.  He noted that this trend appears to be continuing.  I
>would also add that it is my impression that a smaller percentage of federal
>science funding is going to physics.  Does anyone have a source which confirms
>or refutes these facts?  Dale, what does your crystal ball have to say? :-)

    If he said it, it is likely true.  However, what it means and how
    it was determined is anyone's guess.  

    I will point out that the portion of the budget due to things
    like social security and medicare are rising rapidly and that we
    a running a deficit that will probably be larger than $300 billion
    and possibly $400 billion.  So the fact that it may be a smaller
    percentage of a fast-growing budget does not really surprise
    me.

    The numbers, if even true or fair, are hardly a justification for
    ramming protons together at high energy for $10 billion, no disrespect
    to the honorable Mr. Gramm.

    There was a very enjoyable discussion of the SSC on the PBS news
    tonight.  For fans of the project, Dale Bumpers said that he probably
    does not have the votes to defeat it.

                              dale bass


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