HDTenEightyP/NetNews huggingface dataset:
From: gswst@cislabs.pitt.edu (Gary S. Wachs)
Newsgroups: sci.physics
Subject: frustrating physics I problem
Date: 14 Dec 92 23:42:23 GMT
Organization: University of Pittsburgh, Electrical Engineering

I need help with the following physics problem, folks.  It's not homework,
but if you can't take my work for that then maybe you can at least give me
a hint 'cause I'm bashing my head against a wall with this darn thing!
 
A ball is propelled off a mountain-top at an angle of 't' degrees above the
horizontal.  It lands 'y' meters below and 'x' meters in front of the
cliff.
 
It terms of t, y, x, and any other constants you find handy, find:
 
a) the ball's total flight time 't'
b) the initial speed of the ball 'Vo'
c) the maximum height 'h' above the ground that the ball reaches
d) the angle 'p' at which the ball strikes the ground
 
                           ----                     apex
                       /    /\    \ 
                   /         |      \
                / )angle t   |         \
--------------* - - -        |           \          cliff height
     /\       |              |             \
      |       |              h              \
      y       |              |               \
      |       |              |                \
      |       |             \/       angle p ( \
     \/       |/___________ x _________________\*    ground 
              |\                               /
 
 
Many thanks...
Newsgroups: sci.physics,alt.happy.birthday.to.me
From: seanna@bnr.ca (Seanna Watson)
Subject: Happy Birthday Isaac
Organization: Bell-Northern Research, Ottawa, Canada
Date: Wed, 16 Dec 1992 02:58:22 GMT

God rest ye merry, physicists,
Let nothing you dismay,
Remember, Isaac Newton was born on Christmas day,
His gravity and calculus and F = ma,
Oh pillars of physics and math, physics and math,
Oh pillars of physics and math.
-- 
Seanna Watson   Bell-Northern Research, 
(seanna@bnr.ca) Ottawa, Ontario, Canada

Opinions, what opinions?  Oh *these* opinions. | Occam's razor split 
No, they're not BNR's, they're mine.           | hairs so well, I bought 
I knew I'd left them somewhere.                | the whole argument.


Newsgroups: sci.physics,sci.math
From: jbaez@riesz.mit.edu (John C. Baez)
Subject: Re: Why Wave Functions aren't Physical (Was: Re: QM non-causal?)
Organization: MIT Department of Mathematics, Cambridge, MA
Date: Sun, 13 Dec 92 20:42:33 GMT

In article <1992Dec11.220139.14066@newshost.lanl.gov> jlg@cochiti.lanl.gov (J. Giles) writes:
>In article <1992Dec10.192451.9924@lmpsbbs.comm.mot.com>, bhv@areaplg2.corp.mot.com (Bronis Vidugiris) writes:
>|> [...]
>|> P2:  Mathematically, if some measurable phenomenon C affects the
>|> probabilities of both A and B, one can mathematically state that
>|> 
>|> P(A) = intergal of Pa|c() * delta P(C)
>|> P(B) = intergal of pb|c() * delta P(C)
>|> 
>|> where Pa|c is the 'conditional' probability of A given C
>|> (I belive this is known as Baynes thereom)
>
>There are several problems with this.  One is that the formal mathematical
>properties of probability are not necessarily applicable to sub-QM physics.
>The second is that the definition of integration is not clear when the
>underlying functions are not continuous - or, at least, the number of
>discontinuities are infinite (and what proof have you that they are
>continuous?).  There are many other assumptions buried in the math.  
>The idea that conventional mathematics is necessarily applicable to 
>these physical domains is pure speculation.  Even the definition of 
>*multiplication* is a human invention which we have no reason - beyond

The relationship between probability theory and quantum mechanics is far
better understood that Giles seems to imply.  Quantum mechanics can be
thought of as a generalization of classical probability theory, and it's
easy to check in many cases which theorems of classical probability
theory extend to the quantum case.  Irving Segal (who was a statistician
before he went into mathematical physics) developed the formalism of
C*-algebras and noncommutative integration theory in the 40's and 50's
for exactly this reason (among others).  Bayes' theorem holds, in
particular.  (But Vidugiris has not stated Bayes' theorem... maybe he
really DID mean Baynes' thereom!  :-)  Bayes' theorem is that the
probability of F given E is the probability of E given F times the
probability of F divided by the probability of E.)  

Giles' fears about discontinuities and such are uncalled for; measure
theory doesn't really care about discontinuities.  Of course, learning
probability theory, measure theory and C*-algebras takes work, and it
*is* wise to be cautious about this stuff before one has studied it.  

So where to learn this stuff?  Bratteli and Robinson's 2-volume book is
excellent but perhaps a little intimidating.  One could always go to the
locus classicus:

Segal, I. E.  A noncommutative extension of abstract integration, Ann.
Math. 57 p. 407, 58 p. 595 (1953).

Abstract probability spaces and a theorem of Kolmogoroff, Am. J. Math.
76 p. 721 (1954).

A note on the concept of entropy, Jour. Math. and Mech. 9 p. 623 (1960).
From: G.Joly@cs.ucl.ac.uk (Gordon Joly)
Newsgroups: sci.physics
Subject: Re: Can space-time intersect itself?
Date: 15 Dec 92 17:16:03 GMT


The answer probably lies in superstring theory...


Gordon Joly      Phone  +44 71 387 7050 ext 3703      FAX  +44 71 387 1397
Internet: G.Joly@cs.ucl.ac.uk        UUCP: ...!{uunet,uknet}!ucl-cs!G.Joly
Computer Science, University College London, Gower Street, LONDON WC1E 6BT

Newsgroups: sci.physics
From: zellner@stsci.edu
Subject: Re: Why is the sky blue?
Organization: Space Telescope Science Institute
Distribution: na
Date: Tue, 15 Dec 1992 23:30:10 GMT

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

A scientist is tempted to say that these are nonsense questions, but maybe
we should be more generous.  The "why" is a mixture of mathematics, physics,
history, environment, physiology, and culture.  Just a few examples:

Why does the sun have the spectrum it does?  Well the temperature of its
surface is determined (physics) by its mass, age, and original chemical
composition (history and environment).  What particular interstellar cloud
happened to collapse in what particular way, probably triggered by a nearby
supernova that just happened to go off at that particular time?

Then why does a black-body at temperature 5600K radiate the kind of photons 
that it does?  Well the only "physical" parameter in the equation is Planck's
constant.  I think why Planck's constant has the value it does is unknown to
present-day physics, though maybe not forever.

Why does Rayleigh scattering go as the fourth power of the frequency?  I
believe that's fundamentally a mathematical result, like asking why two plus
two equals four.

So why does the earth have a fairly clear atmosphere of uncharged molecules 
of oxygen and nitrogen?  History and environment, as above.

So why do our eyes contain structures specifically sensitive to light of 
wavelength 4300 to 4800A?  Physiology, really accidents of evolutionary history.
And why do we call that color "blue" and not "green"?  Culture. 

So why aren't we here during the red-giant stage of the sun?  That gets us to
the Anthropic Principle.  If all of the above wasn't the way it is (except for
the cultural factor), we wouldn't be here to ask the question!  The fact that 
we are here essentially REQUIRES that the sky be blue.  That's the ultimate 
"Why".

Cheers, Ben.
From: jonathan_scott@vnet.ibm.com (Jonathan Scott)
Date: Sun, 13 Dec 92 15:48:22 GMT
Newsgroups: sci.physics
Subject: Can you find any evidence against this theory
News-Software: UReply 3.0

My question is:

Have real experiments shown any evidence AGAINST a theory which gives
exactly a HALF of the QM correlation for the two-photon experiment?
(This question arises because a proportional decrease in correlation is
difficult to distinguish from background "false coincidence" noise).

The most obvious deterministic model for the two-photon experiment (as I
mentioned a few days ago in the referenced append) predicts exactly half
the QM correlation for photons with random polarization, or the full QM
correlation if either of the detectors is guaranteed to be aligned with
the photon polarization (which occurs for example when observing the
circular components of pure L or R circularly polarized photons which
have not been deflected, as I believe occurred in 3/4 of the path
configurations in the dynamic switch Aspect experiment).

I've tried looking at Phys Rev articles in my local university library
several times but I don't understand enough of the jargon to understand
how Aspect & co. got from the raw figures to the final conclusions, but
terms like "false coincidence" make me wonder how the background noise
is filtered out, and whether the results support equally well any theory
which gives a smaller but proportional correlation.

Jonathan Scott
jonathan_scott@vnet.ibm.com  or  jscott@winvmc.vnet.ibm.com
Newsgroups: sci.physics
From: ruppert@winx06.informatik.uni-wuerzburg.de (ralf ruppert)
Subject: Moessbauer applications searched
Organization: University of Wuerzburg, Germany
X-Newsreader: TIN [version 1.1 PL6]
Date: Thu, 17 Dec 1992 14:08:47 GMT


Newsgroups: sci.physics,alt.psychology.personality,sci.engr
From: noring@netcom.com (Jon Noring)
Subject: Re: Richard P. Feynman
Organization: Netcom - Online Communication Services  (408 241-9760 guest) 
Date: Sat, 12 Dec 1992 01:31:03 GMT

In article schumach@convex.com (Richard A. Schumacher) writes:

>>but I was.  I don't see why I can't enjoy (and understand) both Hannah 
>>Arendt and Oppenheimer or Feynman.  Please recall that Mr. Feynman 
>>specialized in physics but also painted and played the bongos, among many 
>>other endeavours not normally associated with 'scientists'.
>
>Not true!. Many scientists are interested in and appreciative of the arts.
>You must be thinking of engineers.


I believe there is a lot of truth to this.  I work with a lot of engineers,
and the real nuts'n'bolts type are, *on the average*, and with notable
exceptions, much more likely to be not interested in the arts than those who
can be called scientists (the distinction between engineers and scientists can
be blurry if you consider field of study alone - generally Ph.D. engineers are
more likely to be "scientifically oriented", to be much more intuitive.)

A few years ago I worked at Sandia Laboratories in Livermore, and worked with 
probably the best engineer they had (he received the DMTS award, etc.).  All
he cared for was working 8-4, going home, eating dinner, watch a little tv,
go to bed, and then get up the next day to go to work again.  On the weekend,
he really let loose and did things like mow the yard, etc - I think you catch
my drift.  When I asked him once about it, he said that if it paid well, he'd
just as soon work at a factory where he could turn his mind off for eight
hours!  He was a real nice guy, and a brilliant engineer (and Sandia has some
of the best), but outside of engineering he was extraordinarily dull.
(OK, I've crossposted this to alt.psychology.personality:  what is his
probable MBTI personality type?)

Jon Noring

-- 

Charter Member of the INFJ Club.

Now, if you're just dying to know what INFJ stands for, be brave, e-mail me,
and I'll send you some information.  It WILL be worth the inquiry, I think.

=============================================================================
| Jon Noring          | noring@netcom.com        | I VOTED FOR PEROT IN '92 |
| JKN International   | IP    : 192.100.81.100   | Support UNITED WE STAND! |
| 1312 Carlton Place  | Phone : (510) 294-8153   | "The dogs bark, but the  |
| Livermore, CA 94550 | V-Mail: (510) 417-4101   |  caravan moves on."      |
=============================================================================
Who are you?  Read alt.psychology.personality!  That's where the action is.
Newsgroups: sci.physics
From: sarfatti@well.sf.ca.us (Jack Sarfatti)
Subject: PS we may need half-wave plate after all.
Organization: Whole Earth 'Lectronic Link
Date: Sat, 12 Dec 1992 08:17:26 GMT


if we need it - stick it in! That is
|o-> -> |o+>

still by unitarity

<e+|o+> = 0 because <e+|o-> = 0

but the matrix element of S(&).... between e+ and o- might vanish
because of perpendicular polarizations while that between e+ and o+
does not vanish.
From: ynecgan@cid.aes.doe.CA (Greg Neill)
Newsgroups: sci.physics
Subject: Re: (A1) EXPLAINS THE PHYSICS from particle to Galaxies
Keywords: (A1)  12-11-92
Date: 11 Dec 92 20:08:31 GMT
Organization: Environment Canada (CID), Dorval, QC

In article <abian.724093986@pv343f.vincent.iastate.edu> abian@iastate.edu (Alexander Abian) writes:
>To the Readers of TIME HAS INERTIA
>
>Att:  RIEMERS and Indra SINHA
>
>        (A1) EXPLAINS PHYSICS from particle to Galaxies
>
> 
>What Galileo, Newton, Maxwell, Planck, Einstein and Schroedinger
>failed to notice, deduce and conclude is that
>
>    In accordance with (A1) and as (A1) predicts and explains
>
>     THE SPACE ITSELF  AS ANY PARTICLE  TENDS TO MAINTAIN  ITS
>     NEUTRALITY and reacts by trying to annihilate the concentration
>     of particles at any place -  With weak and small particles
>     it succeeds by decaying them explicitly under our eyes; with big 
>     masses the decaying process  takes  TIME.  The  resulting
>     energy is irretrievably dissipated to move TIME forward.


Is this your description for the mechanism of radioactivity?

-- 
------------------------------------------------------------------------------
Greg Neill,               | "Interfere!?! Of course we should interfere!
HNSX Supercomputers  Inc. |  Always do what you're best at, that's what
ynecgan@cid.aes.doe.ca    |  I always say."  - Dr. Who
Newsgroups: sci.physics
From: sidles@stein.u.washington.edu (John Sidles)
Subject: Re: Passive Magnetic Levitation (was: Science Fair Project)
Organization: University of Washington, Seattle
Date: Wed, 16 Dec 1992 21:05:51 GMT

>In article <1992Dec16.163743.24669@asl.dl.nec.com> terry@aslws01.asl.dl.nec.com (Terry Bollinger) writes:
>In article <1992Dec11.202853.8041@murdoch.acc.Virginia.EDU>
>crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass) writes:
>
>> My guess is that torsional perturbations do you in. The levitated [three
>> disk magnets connected by long arms] simply flops out of your carefully
>> arranged [three ring magnets] and proceeds to ... resting on the ground.
>
>Dale is correct.  I was focusing on the arms on the *assumption* that the
>disk-over-ring arrangement was capable of creating a shallow but real
>potential well that provided lateral stability.  After trying it out with
>some real magnets, I'm now convinced that this potential well does not
>really exist, and thus the entire arrangement cannot depend on its lateral
>stability.
>

From a theoretical point of view, here's a simple proof that you
can't levitate either (1) a magnetic moment (like a small bar magnet)
of (2) a small permeable sphere.  My apologies if its already been
posted.  But its simplest to just work it out for yourself.

(1) Both moments and permeable spheres can lower their potential
    energy by moving to a region of greater field strength.

(2) Therefore, the stable position is one at which "B dot B" is
    a local maximum.

(3) If "B dot B" is a local maximum, then "delsquared" "B dot B"
    (where "delsquared" is the Laplacian differential operator)
    must be less than zero.

(4) But on working out the components of "delsquared" "B dot B",
    the terms involving second derivatives vanish (using the
    fact the B is divergence-free and curl-free), and the term
    involving first derivatives are sums of squares, hence positive.

(5) Therefore "B dot B" never has a local maximum in empty space, so

(6) You can't levitate small magnets or small pieces of iron with
    a static field.

However, I can't prove that extended objects can't be levitated.
In fact, it seems likely to me that they can be levitated.

If anyone does it, please post! .... John "question authority" Sidles


---------------------------------------------------------------------
John A. Sidles, Ph.D.               email: sidles@u.washington.edu
Associate Professor                 phone: (206) 543-3690
Department of Orthopaedics RK-10    FAX:   (206) 685-3139
School of Medicine
University of Washington
Seattle WA 98195
---------------------------------------------------------------------
From: gwe3409@bcsaic.boeing.com (Gerald Edgar)
Newsgroups: sci.physics
Subject: Re: Cappucino Noise
Date: 17 Dec 92 15:47:42 GMT
Organization: Boeing Computer Services, Seattle

I have an uninformed opinion about the moise of steam in water:
as steam is realsed into water the steam cools and condences
into water. For cold milk the steam bubles collapse quickly
and make the higher pitched noise. as the milk heats, the
steam cools less quickly and the noise spectrum shifts to
a lower frequency since the bubbles collapse more slowly.
When the milk reaches boiling point the steam bubles do not
collapse at all and you only get the sound of bubbles
collapsing when they reach the surface of the milk.

This is my theory and has no basis other than my opinion
and it seems to fit my observation and assumptions:
mainly that the speed at which steam bubbles collapse
is inversely proportional to tempurature of the milk,
and that as the bubbles collapse they make a shock wave.

Gerald Edgar
gwe3409@bcsaic.boeing.com
"Whose opinion? not my companies-- only my own"
Newsgroups: sci.physics
From: radford@cs.toronto.edu (Radford Neal)
Subject: Re: Special relativity is SOOO irritating!
Organization: Department of Computer Science, University of Toronto
Distribution: sci
Date: 18 Dec 92 17:48:59 GMT

In article <1992Dec18.000855.11867@novell.com> dseeman@novell.com (Daniel Seeman) writes:

>>If you prefer, we can assume that the staff really does impact the wall.
>>In this case, however, one can't assume that the staff is perfectly rigid,
>>since that would require that the impact be propagated to the end of the
>>staff instantaneously. What will happen is that the staff will be compressed
>>(in the intertial frame in which it was previously at rest). We _can_ assume
>>that this is temporary, and that the staff will later rebound to its origninal
>>length. In this case, the answer is that the hatch can be closed, and that
>>the tail end of the staff will smash into it when the staff rebounds to its
>>full one metre length.
>>
>>    Radford Neal
>
>Hey, isn't that pretty much what I said in my posting?  One would see sort of a
>"virtual" rebound as the rod accelerates back into the rest frame of the wall
>and the hatch so the stick would poke back through the hatch.  So, is this idea
>correct or not?

Yes and no. Your original assumption that the staff is stopped by the
wall without being deformed is not just unlikely, but quite
impossible, according to special relativity. You have two choices -
either the staff is stopped by the wall, but is deformed, in a very
real sense, or it is stopped by some other process that leaves it
undeformed, and just happens to come to rest in front of the wall. The
answers in the two cases are different. In the first cases, the rod
does rebound and hit the hatch, but this rebound is not in any sense
"virtual" - it is just as real as the rebound of any other compressed,
elastic object. In the second case, there is no rebound, and you can't
even close the hatch to start with.

    Radford Neal
Newsgroups: sci.physics
From: matmcinn@nuscc.nus.sg (Brett McInnes)
Subject: Re: TIME HAS INERTIA.  (A3) DEDUCES (A5)!
Organization: National University of Singapore
X-Newsreader: Tin 1.1 PL4
Date: Mon, 14 Dec 1992 05:11:31 GMT

tao@fine.princeton.edu (Terry Tao) writes:
: 
: BUT ENERGY IS DISSAPATED BY TIME.  SO TIME IS THE ENEMY OF THE UNIVERSE.
: 
I propose that all further postings on this theme be titled               
        TIME IS A SON OF A BITCH				              : NOW
: 
: ;-) FTHI
: 
Newsgroups: sci.physics
From: crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass)
Subject: Re: Metals in liquid Nitrogen !!
Organization: University of Virginia
Date: Fri, 11 Dec 1992 21:49:59 GMT

In article <1992Dec11.211603.7564@magnus.acs.ohio-state.edu> kpearce@magnus.acs.ohio-state.edu (BULLDAWG) writes:
>In article <Bz4470.4ps@knot.ccs.queensu.ca> polowin@chem.queensu.ca (Joel Polowin) writes:
>>In article <1992Dec11.200321.6333@magnus.acs.ohio-state.edu> kpearce@magnus.acs.ohio-state.edu (BULLDAWG) writes:
>>
>>>Go back to fundimental chemistry.  Phase changes are generally exothermic.
>>
>>Um.  Exactly half of them are exothermic.  The other half are endothermic.
>>:-)
>>
>
>I don't think I ment that the reactions in the reverse direction are
>distinct.

     Then 'all' of them are endothermic as well?

                          dale bass
-- 
C. R. Bass                                          crb7q@virginia.edu        
Department of Mechanical, 
     Aerospace and Nuclear Engineering
University of Virginia                              (804) 924-7926
Xref: sparky sci.physics:20961 talk.bizarre:41314