HDTenEightyP/NetNews huggingface dataset:
From: jac@ds8.scri.fsu.edu (Jim Carr)
Newsgroups: sci.physics
Subject: Re: Why is the sky blue?
Date: 16 Dec 92 19:11:10 GMT
Reply-To: jac@ds8.scri.fsu.edu (Jim Carr)
Distribution: na
Organization: SCRI, Florida State University

In article <1992Dec15.135457.13692@linus.mitre.org> m14494@mwvm.mitre.org (Mike White) writes:
>> In that case the classical Rayleigh theory ...
>> ... x = 2 pi a / lambda...
>> ...spectrum of the sun convolved with a fourth-power law...
>> Rayleigh scattering...
>
>All this talk about scattering etc. just misses the point.  We all
>understand *how* the sky is blue, but the question is *why*?

Because those of us who speak English associate the word blue with 
the stimulus produced by those cones in our retina which are mainly 
sensitive to photons at the upper end of the "visible" spectrum, 
and these photons are more numerous than those detected by the cones 
sensitive to other parts of the "visible" spectrum because the 
spectrum of photons produced by thermonuclear fusion in our sun, 
moderated by its photosphere, is altered by Rayleigh scattering 
in the Earth's atmosphere, which is mainly nitrogen and oxygen for 
reasons having to do with the geologic and biological history of 
this planet and the distance of its orbit from its sun. 

Is that better?  Hmmmm?

>The mechanism that makes it blue is clear, but why does that
>mechanism exist instead of one that makes it, say, green?  Yes,

Or ultra violet.  Actually, there may be people who see it as green 
due to some defect in their retina, but they also probably call it 
blue because everyone tells them "the color of the sky is blue". 
After all, I will guarantee you that the color of the sky I see here 
on a clear winter's day is different from what is seen in the mountains 
or at a more northerly latitude. 

>yes, I know: "physics describes, it does not explain".  I've always
>found that answer to be a cop-out (as we used to say back in the
>60s).  I think "why" is an excellent question.

I would add that physics does explain some of these things.  For instance, 
the biochemistry of carbon-based life requires certain atmospheric properties 
and temperatures.  Physics explains how the atmosphere moderates the climate. 
It places some limits on the properties of photoreceptors and the spectrum 
of photons that illuminate the earth's surface.  It cannot, of course, 
explain why the Weinberg angle and the neutron-proton mass difference is 
just right for things to turn out the way they did.....

--
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)
Organization: Senior, Physics, Carnegie Mellon, Pittsburgh, PA
From: acampane@magnus.acs.ohio-state.edu (Angelo Campanella)
Subject: Re: Pressures inside a boiler.
Organization: The Ohio State University
Date: Sat, 19 Dec 1992 07:31:21 GMT



1/ Use Mark's Mechanical Engineer's Handbook, any edition, to get some basic
working equations and some graphics that may aid modeling.

2/ Remember that the triple point of steam is about 600 degrees F and 600 PSI.

(Triple point is where the density of the steam and of the water is the same; 
the whole vessel fills up with very hot and very dense vapor; no meniscus!)

Luck!
From: ynecgan@cid.aes.doe.CA (Greg Neill)
Newsgroups: sci.physics
Subject: Re: TIME HAS INERTIA - ABIAN REPEATS overwhelmingly demanded (A3)
Summary: ABIAN repeats OVERWHELMINGLY
Keywords: pschology, crank, blithering idiots
Date: 16 Dec 92 19:36:27 GMT
Followup-To: sci.physics
Organization: HNSX Supercomputers

In article <BzD4v8.J31@news.cso.uiuc.edu> met48546@uxa.cso.uiuc.edu (Marc E. Talbot) writes:
>abian@iastate.edu (Alexander Abian) writes:
>
>>   I COUNT ON BRILLIANT  READERS OF  TIME HAS INERTIA AND THE YOUNG
>>IMAGINATIVE AND AGGRESSIVE MINDS FOR DEVELOPING AND INTRODUCING
>>(A1), (A2), (A4)  based on the CORNERSTONE OF THE NEW REVOLUTION IN THE 
>>PHYSICS  -  (A3)
>>   I was told that in Russia they are very seriously considering the
>>ramifications and implication of  TIME HAS INERTIA - very seriously,
>>without sarcasm, without childish kiddings, without putting me down
>>without sardonic remarks, without mockery, without vilification,
>>without slander and wretched brutish and beastly envy and hostility.
>
>Told by whom?  What research group?  What university?  Are you sure someone's
>not just sending you fake Email?  Or are you just making this up?  Come on,
>answer this one....
>


  It might be interesting to note that the last refuge of the hopelessly
deluded is to assert that they have gained enormous support from a
growing following of "true believers" in some far off place, usually 
claims which cannot be substantiated or refuted without undue effort.

  Note that in this instance the deluded one names no names, quotes no
quotes, and makes nothing but vague references.  Typical.

  Time to refer the patient to sci.psychology?  Could be worth a term
paper or two to someone with nothing interesting to do.

-- 
------------------------------------------------------------------------------
Greg Neill,               | "Man is certainly stark mad.  He can't make a worm,
HNSX Supercomputers   Inc.|  but he makes gods by the dozens."
ynecgan@cid.aes.doe.ca    |                      -- Montaigne
Newsgroups: sci.physics,alt.sci.physics.new-theories,alt.fan.warlord
From: kibo@world.std.com (James "Kibo" Parry)
Subject: Re: Ramsay's "Sorry Sarfatti".
Organization: Two rooms filled with typography, in downtown Boston
Date: Wed, 16 Dec 1992 07:30:34 GMT

In article <BzBwsx.8zz@well.sf.ca.us> sarfatti@well.sf.ca.us (Jack Sarfatti) writes:
>          _____________________
>        /     1+                \
>------/ I                      II \___________
>      \                           /
>        \_____2-_____|_|________/
>                 spin flip

This is the worst ASCII Australia map I've ever seen in a .signature.

								-- K.
From: tabitha@vms.huji.ac.il
Newsgroups: sci.physics
Subject: quantum cosmology
Date: 13 Dec 92 17:16:44 GMT
Distribution: world
Organization: The Hebrew University of Jerusalem

A question about quantum cosmology from a non-physicist.

If space and time came into existence with the big bang, in
what would the quantum fluctuation have occured?

-dennis turner
tabitha@vms.huji.ac.il
Newsgroups: sci.physics
From: wft@math.canterbury.ac.nz (Bill Taylor)
Subject: Re: Bayes' theorem and QM
Organization: Department of Mathematics, University of Canterbury
Date: Tue, 15 Dec 1992 02:08:09 GMT

In article <1992Dec14.003452.12884@galois.mit.edu>, jbaez@riesz.mit.edu (John C. Baez) writes:

|> I feel like adding that Bayes' theorem is a blatantly obvious
|> consequence of the following *definition* of conditional probability:
|> 
|> P(E|F) = P(E&F)/P(F).
|> 
|> and with a little algebra we get Bayes' formula:
|> 
|> P(F|E) = P(E|F)P(F)/P(E).
|> 
|> Thus while Bayes' theorem is very beautiful and sometimes has
|> unintuitive consequences, it's also utterly trivial.

Almost right. It *is* fairly trivial, in the sense you say; and that's something
I always tried to stress to students, (usually with juicy snide digs at
economists, sociologists and other non-mathematicians who seem to think there
is something magical about Bayes theorem.)

However, to be fair, there is just *slightly* more to Bayes theorem than the
above, as it is usually presented.  The missing ingredient is the idea of a
partition of the sample space.

We usually have not just one "F", above, but partition  F1, F2, ... , Fn.
(The partition can later be extended to countable, then continuous.)

Then it becomes

P(F|E) = P(E|F)P(F)/P(E).
~ ~      ~   ~ ~ ~
...where the underlining is as usual for vectors; though the product on the RHS
is just pointwise, not dot-product.  This also stresses that E (the "evidence") 
is a single event, whereas F is a whole range of possibilities, the true one
never being isolated.      ~

So Bayes theorem is still (almost) trivial, being a mixture of the definition
of conditional probability, and the summing of probabilities over a partition
[ which is hidden in the last P(E) ]. 

-------------------------------------------------------------------------------
              Bill Taylor              wft@math.canterbury.ac.nz
-------------------------------------------------------------------------------
                    All finite math is essentially trivial.
                    All continuum math is essentially false.
-------------------------------------------------------------------------------
Newsgroups: sci.physics
Subject: Re: Magnetic question (again!)
From: kiran@gacvx2.gac.edu
Date: 19 Dec 92 19:14:27 -0600
Organization: Gustavus Adolphus College, St. Peter, Minnesota

In article <1992Dec17.183821.13124@topaz.ucq.edu.au>, freeman_l@topaz.ucq.edu.au writes:
> 
> Here's another dumb question about electrodynamics......
> 
> How does a charged particle "know" how fast it is moving through
> a uniform magnetic field, if the field is completely uniform and
> featureless?  
> It's a bit like this.... If you wipe your hand over a perfectly smooth
> tabletop, then it feels the same whether you move slowly or quickly.
> 
> Similarly,  if there is no structure in a magnetic fild that the particle
> can reference and say "ah, yes! i have passed so many of these field
> lines in such and such a time, i must be travelling THIS fast...so i
> should be experiencing such and such a force...."
> 
> I realize this is a sloppy way of saying it, but I still can't make a
> logical link between an electron's motion relative to a magnetic field,
> and the amount of force exerted on the electron.
> 
> The reason for this is the realization that while an electron may be
> blithely oblivious to it's own velocity in a straight line, (that depends
> on the observer), an acceleration , on the other hand is a very real,
> measurable thing to the particle.
> 
> That leads me to the following conclusions-:
> 
> A magnetic field must somehow provide a frame of reference for a charged
> particle.
> Not only that, but the field/particle system must also be aware" of time,
> because it can distinguish between fast motion and slow motion.
> 
> A magnetic field can move around in space. This seems at first thought to be
> a pretty obvious statement, but.... WHAT is actaually moving? Has a magnetic
> field got some fine internal structure, like the Classical lines of Force,
> so that you can say: THIS bit of the magnetic field is now over HERE!
> 
> It's hard to put these concepts into words, but I hope
> that you'll get the gist of what I'm saying.
> 
> PS I'm a programmer, not a physicist. (Face-saving admission).
> 
> Leo Freeman
> Physics Dept.
> Uviversity of Central Queensland,
> Rockhampton, QLD, Australia.
> 
Newsgroups: sci.physics
From: sawyer@utahep.uta.edu (Lee Sawyer)
Subject: Re: Here is what I meant about the kill files...[BINGO !]
News-Software: VAX/VMS VNEWS 1.41    
Organization: University of Texas at Arlington High Energy Physics Group
Date: Tue, 15 Dec 1992 19:14:00 GMT

 THANKS TO Michael J. Corrigan AND Jack Shirazi :

 The following works in VNEWS

/TIME HAS INERTIA/

       ================                           
         Lee Sawyer                                  

         Dept of Physics                          
         Univ. of Texas                            
               at Arlington                        

Newsgroups: sci.physics
From: kpearce@magnus.acs.ohio-state.edu (BULLDAWG)
Subject: Re: Why is the sky blue?
Organization: The Ohio State University
Date: Mon, 14 Dec 1992 19:05:41 GMT

In article <Bz80y2.Mw@news.cso.uiuc.edu> cburian@ux4.cso.uiuc.edu (Christopher J Burian) writes:
>Actually, I know *why*, ie. scattering... but why specifically blue?
>Does it matter what molecules are in the atmosphere, or just that
>there happens to be an atmosphere?


It is blue because gases scatter (inelasticly) photnons in a manner that
is goes as some power >2 (to an approximation) with the photon energy.
Since blue is the highest energy photon that our eyes can see, that is the
frequency that is scattered the most, and thus the frequency that we 
actually observe.  Of course for this effect to be observable, the gas would
need to be colorless, such as O2, N2, He, H2, etc.

>
>Would all planets with air breathable by earth creatures have to
>have blue skies?  (Referring to green/brown/orange skies so 
>prevalent on Star Trek)

Unless there was something else in the air such as dust from fall-out.

>
>I've seen pictures of Mars where the sky and ground were orange,
>and others with brown rocks and a blue sky.  What color is the
>sky on Mars? 

I remember seeing a photo where they showed that at the right angle one
could see that Mars has a blue sky, but mostly it looks black because the
athmosphere is so thin.

>
>Thanks for letting me indulge in stupidity.
>

I don't think it's a stupid question   }:)

Organization: Doctoral student, Urban and Public Affairs, Carnegie Mellon, Pittsburgh, PA
Newsgroups: sci.physics
Date: Fri, 18 Dec 1992 17:50:01 -0500 
From: Lawrence Curcio <lc2b+@andrew.cmu.edu>
Subject: Re: TIME HAS INERTIA - ABIAN replies to POLOWIN

It must be true. The more time this thread absorbs, the more inertia it
acquires.
From: wolf@doppel.first.gmd.de (Wolfgang Koehler)
Newsgroups: sci.physics
Subject: Re: Special relativity is SOOO irritating!
Date: 17 Dec 92 23:45:05 GMT
Reply-To: wolf@first.gmd.de
Distribution: sci
Organization: GMD-FIRST, Berlin
In-reply-to: d91andiv@IDA.LiU.SE's message of 15 Dec 92 22:47:47 GMT

In article <D91ANDIV.92Dec15234743@astmatix.IDA.LiU.SE> d91andiv@IDA.LiU.SE (Anders Ivner) writes:

   Consider a staff, one meter long. Now, given the speed v it 'shrinks'
   to half a meter. We then have a wall, and an easily controllable
   hatch placed .75 meters from the wall. The staff passes through the 
   hatch, and we close the hatch behind it (BEFORE it hits the wall!)
   The staff hits the wall, without being deformed (somewhat unrealistic!),
   and since its speed now changes to 0 it is now fully 1 meters long.
   What the **** happens????

Hello Anders,
you should read the sci.physics FAQ. It contains a similiar "paradox"
of SR, called "the barne and the pole". (And of course it's solution)
If you missed the FAQ, send me an email, I'll send it to you.

with greetings

wolf

--
-------------------------------------------------------------------------
    ... always look on the bright side of life ... (Monty Python)
-------------------------------------------------------------------------
Wolfgang Koehler                               wolf@first.gmd.de
GMD-FIRST an der TU Berlin              German National Research Centre 
Tel. (Berlin 030/049) 6704-2650              for Computer Science



Newsgroups: sci.physics
From: ST402676@brownvm.brown.edu
Subject: Re: Metals in liquid Nitrogen !!
Organization: Brown University
Date: Sun, 13 Dec 1992 13:31:02 GMT

>The nitrogen will boil for some time, like it boils when you drop anything
>in it, but then suddenly it will boil really hard, about 3 times more
>violently than it did before, for about half a second, and then it will
>just gently bubble away (When the metal is in thermal equilibrium with it,
>i guess...).
>
>	WHY ???????????????
>	WHY JUST METALS ???
>	

I am surprised no one has pointed out that the effect isn't unique to metals.
Ever pour lots of nitrogen ito a warm dewar? At first it boils moderately,
as it cools the glass but only through vapor. Then, it will suddenly boil
violently (liquid touches the walls) and then settle into its normal
quiet boil.

The same effect allows you to dip your finger into liquid nitrogen. If you
just dip it in and out, you won't even feel cold, as the vapor insulates
the finger from the liquid. Don't test how long you can leave it, because
when the liquid gets to the finger, you will be very unhappy.

Tamar (who thinks anything over a few mK is hot)
From: dseeman@novell.com (Daniel Seeman)
Newsgroups: sci.physics
Subject: Re: Annual Unintentional sci.physics Humor Award
Date: 14 Dec 92 18:05:53 GMT
Organization: Novell Inc., San Jose, Califonia

In article <Bz4w2D.GJE@news.cso.uiuc.edu> dnash@uxa.cso.uiuc.edu (Dave Nash) writes:
>Envelope please...thank you.  And the winner is... (rip):  Geez, can't you 
>guess by now?
>
>I have, in the past, wondered whether Abian was serious, a dreadful practical
>joker, merely bizarre, or the result of an AI experiment gone amuck.  Nope.
>None of the above.  In fact, the following paragraph dispells all doubt:
>
>>  You have to surrender to (A3), you have to introduce (A3) as the prime
>>principle of Physics as the CORNERSTONE of modern PHYSICS .  You have no
>>other choice!  No matter how you twist and twirl around to bend the inter-
>
>Ah!  It becomes clear now.  Abian is a Borg.  (Molecules are irrelevant! 
>Physics is futile!)
>
Funny!  That is just what I was thinking too!..."We WILL assimilate you..."

dks.
From: jac@ds8.scri.fsu.edu (Jim Carr)
Newsgroups: sci.physics
Subject: Re: When your sun forges iron...
Date: 17 Dec 92 18:52:23 GMT
Reply-To: jac@ds8.scri.fsu.edu (Jim Carr)
Organization: SCRI, Florida State University

In article <1992Dec17.081331.21425@u.washington.edu> lamontg@stein.u.washington.edu (Lamont Granquist) writes:
>
>In fact what happens is that you get a buildup of Fe-56 in the core.  After
>the pressure gets great enough the Fe-56 begins to start to fission.
>
>This is bad.

No, it is wrong.

The iron does not fission.  It just sits there.  Since no more fusion is 
taking place, no energy is released, and there is no longer any radiation 
pressure to oppose the gravitational attraction and the star collapses on 
itself until the nucleons reach a density where they feel the repulsive 
short-range core in the nucleon-nucleon interaction.  They "bounce" off 
of this repulsive potential, leading to the explosion of the star.  Along 
the way, electron capture occurs as well, producing the excess neutrons 
needed for r-process nucleosynthesis and the characteristic neutrino 
pulse detected from the most recent nearby supernova. 

Fe-56 cannot fission any more than it can fuse.  It is at the bottom 
of the binding energy curve.   

--
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: weeks@hpscit.sc.hp.com (Greg Weeks)
Date: Fri, 18 Dec 1992 00:57:00 GMT
Subject: Axiomatic Quantum Gravity
Organization: Hewlett-Packard, Santa Clara, CA
Newsgroups: sci.physics

Not.  There is no axiomatic quantum gravity.  General relativity doesn't
have local observables.  I've never seen this asserted, so I'm asserting it
in this note.  The following argument is a bit shaky.  My hope is that
exposure will cure it or kill it.  So, here is why I say that general
relativity doesn't have local observables.


In special relativity, the metric g is viewed as a part of space-time.  The
isomorphisms of space-time make up the Poincare group.  All observables are
Poincare-invariant.  (It's obvious that no experimental result would be
changed if the universe were uniformly translated two feet in some
direction.)  And yet the "observables" of special relativistic theories --
the energy-momentum tensor, the electromagnetic field, the electric
current, and so on -- are Poincare-covariant, not Poincare-invariant.  The
resolution is that it is possible to establish physical coordinate systems
using clocks, yardsticks, and such.  These coordinate systems do not affect
the systems being observed, and vice versa.  The values of
Poincare-covariants measured with respect to a physical coordinate system
are Poincare-invariant.

In general relativity, the metric g is not viewed as a part of space-time.
The isomorphisms of space-time are the diffeomorphisms.  All observables
are diffeomorphism-invariant.  Now, is it possible to establish physical
coordinate systems?  I don't think so.  [Here is where things get shaky.]
If the physical coordinate system is much more massive than the system
being observed, then it will significantly affect the system being
observed.  If the physical coordinate system is much less massive than the
system being observed, then it will be significantly affected by the system
being observed.  So, the notion of a physical coordinate system is
problematic at best.  My feeling is that the notion doesn't make sense.
So, without local diffeomorphism-invariants and without physical coordinate
systems, there are no local observables.

And without local observables, there is no quantum theory, leaving me
feeling as sick as mud.


Incidentally, it is reasonable to ask: If there are no local observables in
general relativity, why does it seem as if there are?  There is an answer
to this.  In practical circumstances, space-time is very nearly flat.  It
is natural to consider coordinate systems in which the metric g is very
nearly the same as in special relativity.  This restricts the symmetry
group of space-time to the Poincare group plus "infinitesimal"
diffeomorphisms.  Furthermore, in the systems where gravity is considered,
massive objects move very slowly (compared to light).  And it just so
happens that, to first order in these velocities, the equations of motion
of massive bodies are invariant under the infinitesimal diffeomorphisms.
So, to a good approximation, in practice we have flat space-time with
Newtonian gravitation.  This influences our intuition.


Greg Weeks
Newsgroups: sci.physics
From: bcr@cernapo.cern.ch (Bill Riemers)
Subject: Re: TIME HAS INERTIA - PLEASE IGNORE ALEXANDER ABIAN 
Organization: CERN, European Research Center for High Energy Physics
Date: Sun, 13 Dec 1992 12:45:31 GMT

In article <21765.723981323@jinr.dubna.su> vignat@lnp01.jinr.dubna.su writes:

>  Don't consider please my little remark as an intention to share your
>  Nobel Prize. I am absolutely sure, that it is you, who should get it.

I admit I was playing this game just as hard as everyone else.  i.e.
Inflatting Alexander's ego by pretending to go along with him, and
then presenting a new arguement to see how he would react.  However,
it is now clear to me that this is long past the point of being funny.
This person has serious problems and we are only making him worse!
Unfortunately, there is no way we can get help for Alexander Abian,
so our best bet is to ignore him until he gets borred with this
idea.  Then he may seek out help, or he may pick-up on another 
bizzare idea.  However, maybe next time he will pick a way of
presenting his idea that allow people to force him to get help.

                           Bill


--
"Yeti!  Saw them in the London Underground twenty years ago.  Ghosts!
A headless woman used to walk through my bedroom at midnight.  Mermaids?
Grandpa was rescued from the Marie Celeste by one.  Vampires?  I always
wondered where my dad went to at night.  Telepathy?  Right now you're
thinking that I'm talking crap.  So what can you tell me that I won't
believe in?" - Andrew Hunt, "CAT'S CRADLE: WITCH MARK"
Newsgroups: sci.physics