HDTenEightyP/NetNews huggingface dataset:
From: johan@blade.stack.urc.tue.nl (Johan Wevers)
Newsgroups: sci.physics
Subject: Re: Uncertainty Principle
Date: 4 Sep 92 15:05:27 GMT

prim!dave@germany.eu.net (Dave Griffiths) writes:
>
>I just read (Stephen Hawking) a nice explanation of the Uncertainty Principle:
>to measure the position accurately, you need very short wavelength photons
>which will have such a high energy that they will bash the particle so hard
>that it's momentum becomes uncertain.
>
>My question is, is this explanation a simplification for laymen, or is that
>how the UP was really derived?

I thought that this was the first way the UP was derived, but it is not
correct. The UP in essential for the wave formalism from the QM. The
interpretation of the uncertaincy is even today a subject for discusion,
and IMO Bohr was wrong about it (He explained by disturbing one thing
while measuing the other).

From the formalism of QM, you can derive the Robertson equation:

\Delta A \Delta B \geq \frac{1}{2}|<[A,B]>|

where \Delta A = \sqrt{<A^2>-<A>^2} is the standard deviation in the
probability distribution of the observable A, [A,B]=AB-BA is the
comutator of A and B. From this point on, it is very easy to derive
\Delta x \Delta p_x \geq \frac{1}{2}\hbar   and
\Delta E \Delta t \geq \frac{1}{2}\hbar   if you use
p_x -> -i\hbar\frac{\partial}{\partial x} and 
E -> i\hbar\frac{\partial}{\partial t}.

The only thing the UP says is that two probability distributions from
two non-cummuting observables can't become both arbitrarly narrow.

> I thought that the UP was somehow more
>"fundamental" and not just related to practical difficulties of measurement.

That's correct. The uncertancy in the measurement is something totaly
different.

>Does it make any sense to talk about a particle having an unknowable, but
>precise, position and momentum (which would be the case if the problem was
>simply one of measurement)?

Yes, but it is trickey. This is exactly the point the EPR experiment was
pointing on. Aspect's experiments prooved that this interpretation
should be handled with care, but some non-causal or non-local hidden-
variable theories exist which reproduce QM.

>Dave Griffiths

******************************************************************** 
* J.C.A. Wevers                *         u\  _\       /e+        2 * 
* johan@blade.stack.urc.tue.nl *     1 |   \ u \  X  /         |   * 
******************************** P = - |    >   >---<     + ...|   * 
*     The only nature of       *     N |   /   /     \         |   * 
*     reality is physics       *         u/   /d     u\            *
********************************************************************
From: bweiner@ruhets.rutgers.edu (Benjamin Weiner)
Newsgroups: sci.physics
Subject: Re: Report on Philosophies of Physicists
Date: 28 Aug 92 18:08:10 GMT
Organization: Rutgers Univ., New Brunswick, N.J.

Barry Merriman writes:
>Oh my god, what have we done!
>
>But, I'd think that if you learned anything from the survey, it
>would have been that this mushy, warm fuzzy [F. Capraesque :-)]
>philosphy is not the way to understand nature.

>Why not become a _real_ scientist, instead of an intellectual gadfly.

No fair, Barry, it seems to me that _was_ what Shoshana Billik deduced
from the survey.  There's nothing too disrespectable about metaphysics
(or even intellectual gadflies), why shouldn't people major in
philosophy if they want to.

Like many of us, I imagine, I am sometimes quizzed about the Tao of 
Physics and other such silliness, or about, say whether Einstein
proved that everything is relative.  Rather than dismiss the questioner
as a fuzzy-head or someone with a hidden New-Age agenda, I try to
carefully explain why I don't agree with that kind of stuff, and
to explain what the science really is, and emphasize the limitations
of it: you can't use physics to justify a moral/philosophical stance
like "everything is relative," etc.  Sometimes it works.  If
scientists want their public image to improve they have to spend more
time explaining what they do - otherwise Fritjof Capra will do it for us.
From: columbus@rachmaninoff.think.com (Michael Weiss)
Newsgroups: sci.physics
Subject: Re: Less Groups! More Representations! (was: Symmetries, groups, and categories)
Date: 4 Sep 92 09:53:52
Organization: Thinking Machines Corporation, Cambridge MA, USA
Distribution: na
	<1992Aug25.045603.13611@nuscc.nus.sg>
	<COLUMBUS.92Aug25114146@strident.think.com> <22035@galaxy.ucr.edu>
	<mcirvin.715559228@husc8>
NNTP-Posting-Host: rachmaninoff.think.com
In-reply-to: mcirvin@husc8.harvard.edu's message of 3 Sep 92 22:27:08 GMT

In article <mcirvin.715559228@husc8> mcirvin@husc8.harvard.edu (Mcirvin) writes:


   Indeed, the first course I took in abstract algebra dealt *only* with
   finite Abelian groups!  We thought a lot about factoring things into
   Z sub n's.  I didn't know what a representation was until grad school.

Only finite Abelian groups?! Matrix groups were not even mentioned? (I
don't mean anything elaborate, just the bare fact that, say, GL(n) is an
example of a group.)  How about Cayley's theorem?
Newsgroups: sci.physics
From: firth@sei.cmu.edu (Robert Firth)
Subject: Re: Rotating Bucket of Water in a Gravitation Field
Organization: Software Engineering Institute
Date: Mon, 31 Aug 1992 12:04:25 GMT

In article <ZOWIE.92Aug30125336@daedalus.stanford.edu> zowie@daedalus.stanford.edu (Craig "Powderkeg" DeForest) writes:

>A better way to do it is [am I giving this away?] to transform into a
>better reference frame where there isn't any motion; since this will
>be a non-inertial frame, there'll be fictitious forces in it that (in
>general) vary with position.
>
>From there, you can use variational techniques (see _The_Feynman_Lectures_,
>II-19, p. 3 for a description) to find the shape of the surface.

And you can take another shortcut.  In the rotating frame of reference,
the fluid is motionless, and is acted on by a constant downward force,
G, and an outward "centrifugal" force Cr that is linear in r.  Since
the surface is still, it must be an equipotential surface, ie everywhere
normal to the resultant force.  Hence, the slope of the surface varies
linearly as r, and the surface itself therefore varies as r^2, ie is
parabolic.  Since the system has axial symmetry and has zero outward
force in the middle, the surface must be a paraboloid of revolution
with apex at the origin and symmetric about the vertical axis.
From: sichase@csa1.lbl.gov (SCOTT I CHASE)
Newsgroups: sci.physics
Subject: Re: Radioactivity and Superstition; was: Re: Are Your Light Bulbs Radioactive?
Date: 3 Sep 92 19:01:58 GMT
Organization: Lawrence Berkeley Laboratory - Berkeley, CA, USA
Distribution: na
Reply-To: sichase@csa1.lbl.gov
NNTP-Posting-Host: 128.3.254.196
News-Software: VAX/VMS VNEWS 1.3-4   

In article <185ecnINN19p@hpsdlss3.sdd.hp.com>, johno@sdd.hp.com (John Ongtooguk) writes...
> 
>  I haven't read the book but being a stupid layman I thought it time
>  to speak up. I have a basic understanding of radioactivity, I'm not 
>  alarmed about any sources that I'm likely to encounter, I have
>  handled low level sources like tritiated thymidine during work on 
>  dna characterization, and I think that the primary reason for fear

Actually, if we worry about radation at all, it should be about things
like tritium.  Tritiated water, which is the starting point for the manufacture
of tritiated organics, is very hard to contain.  Water, as everyone knows,
evaporates and generally gets everywhere.  It is also commonly ingested.

Here at LBL, the Bevalac produces immeasurably small radation hazard to the
local community.  But the tritium labelling facility that we have regularly
releases measurable amounts of tritiated water into the environment - always
within Federal limits, of course, and closely monitored at stations all around 
the perimeter of the Lab.

-Scott
--------------------
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
Newsgroups: sci.physics
From: platt@watson.ibm.com (Daniel E. Platt)
Subject: Prigogine Citation Request
Date: Thu, 03 Sep 1992 15:46:34 GMT
Disclaimer: This posting represents the poster's views, not necessarily those of IBM
Organization: IBM T.J. Watson Research Center

Hi,

I understand Prigogine published some papers on foundations of
stat mech where he explored the problem that ergodic systems
will eventually return arbitrarily close to their initial
state from the standpoint of quantum mechanics.  If anyone
happens to know where he actually discussed these issues,
I'd appreciate citations.

Thanks!

Dan
From: balbes@ohstpy.mps.ohio-state.edu
Newsgroups: sci.physics
Subject: Re: My son would like to know about photons...
Date: 27 Aug 92 10:11:50 EDT
Distribution: na

In article <5156@dove.nist.gov>, gilligan@bldrdoc.gov (Jonathan Gilligan 303-497-3861) writes:
> There is a device called an optical parametric oscillator that will
> split a photon into two photons of lower energy. However, this is
> somewhat pedantic and Scott's answer is probably closer to the spirit
> in which your son asked his question.

Does these two photons retain all the properties of the original.  E.g.
besides just conserving energy and (I would imagine) momentum, do
they retain the original polarization?
Newsgroups: sci.physics,alt.sex
From: m14494@mwvm.mitre.org (Mike White)
Subject: Re: BAROMETERS (was Re: Subject?)
Organization: The MITRE Corporation
Distribution: na
Date: Wed, 2 Sep 1992 17:21:57 GMT

The Myth writes:
>> Your task is to determine the height of the building [given a barometer]

> 1) go to the building superintendant.  Tel him (her?), "I will give this
> barometer to you if you tell me how high the building is."

Excellent.... clap clap clap!  I never thought of that.

> 2) climb to the top of the building.  Throw the barometer off and time 
how
> long it takes to hit the ground (really you should drop it). y=.5*g*t**2.

Non-obvious, but I thought of this one too.

> 3) pace a certain distance out from the building.  Put the barometer on
> the ground.  Measure the height of the barometer.  Measure the angle 
between
> the ground and the line connecting the tops of both.  Use Trig to 
calculate
> the height.

Disallowed: you are not given a ruler. If you assume a ruler, why not
a surveyer's transit, and cut right to the chase?

> 4) tie a rope to the barometer and lower it off of the top of the 
building.
> mark the height of the building on the rope.  measure the rope.

Disallowed: no rope. See above; if a rope, why not a radar altimeter?

> 5) As above, but swing the barometer in pendulum fashion.

Disallowed: no rope (but very slick; I didn't think of this one)

> 6) Measure air pressure at the bottom and at the top.  find the density
> of air as a function of temperature and elevation.  measure the 
temperature
> at top and bottom.  Calculate the pressure.

The obvious one.

> 7) Build an adjustable catapault (variable launch speeds and angles).  
put
> the barometer in the catapault and launch towards building.  Repeat until
> the barometer just clears the top.  use the launch velocity and the 
distance

Disallowed: if you can invoke the time, money, and labor to
built and calibrate the catapault, why not just hire a surveyer
to tell you the answer.

Hmmm... 3 out of 7 by my count.  You get extra credit for
#1 and #5.

************************
* These are my opinions only.*
************************
From: sichase@csa3.lbl.gov (SCOTT I CHASE)
Newsgroups: sci.physics
Subject: Re: Why do protons outnumber antiprotons?
Date: 4 Sep 92 03:02:45 GMT
Organization: Lawrence Berkeley Laboratory - Berkeley, CA, USA
Distribution: na
Reply-To: sichase@csa3.lbl.gov
NNTP-Posting-Host: 128.3.254.198
News-Software: VAX/VMS VNEWS 1.3-4   

In article <3SEP199220131399@zeus.tamu.edu>, dwr2560@zeus.tamu.edu (RING, DAVID WAYNE) writes...
>sichase@csa3.lbl.gov writes...
>>This interpretation is about 50 years out of date.  Consider a simple
>>process, beta decay:  n -> p + e + nu.  How does your picture account
>>for the production of an electron without leaving a positron around somewhere?
> 
>For one thing it's an antineutrino, which is just a different component
>of the positron-antineutrino SU(2) doublet. So this example is a little
>unfair. I think the real problem with the hole theory is that bosons
>also have antiparticles, and the 'sea' can't fill up because there's no
>exclusion principle.

I don't understand your objection.  Can you elaborate?  You're not 
just worried that I wrote "nu" for the antineutrino, are you?  In
my example of beta decay, production of the electron should leave an 
electron hole, which appears as a positron.  Since this does not happen, 
I think that this is a pretty good example of what's wrong with thinking
of antiparticles as the holes left behind when you pop a particle out
of the Dirac sea.

-Scott 
--------------------
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
Newsgroups: sci.physics,sci.environment,misc.consumers
From: schow@bqneh23.bnr.ca (Stanley T.H. Chow)
Subject: Re: Radioactivity and Superstition; was: Re: Are Your Light Bulbs Radioactive?
Organization: Bell Northern Research Ltd, Ottawa
Date: Fri, 4 Sep 1992 15:02:41 GMT

In article <betel.715614400@camelot> betel@camelot.bradley.edu (Robert Crawford) writes:
>de5@ORNL.GOV (Dave Sill) writes:
>>>I stand corrected by John De Armond.  I believe his figures, but I'll
>>>undercut his price.  I'll eat as many as Jym Dyer will supply at a mere
>>>$5k a bulb.  See Jym, we capitalists really do compete.
>>If the threat is as insignificant as you say, why not do it for a nominal fee?
>>$5000/bulb is awfully high for a threat supposedly on a par with a banana.
>
>	Regardless of the health threat, there is the fact that it's
>unpleasant to force feed yourself bits and pieces of light bulbs.
>However, I am willing to do it for $2.5k...

People (or should I say "fellow capitalist scumbags"?), this 
undercutting is getting out of hand! Pretty soon we will be 
paying for the privledge of eating the disgusting light-bulb bits
that are RADIOACTIVE!

We must not allow this to happen. I mean, where's the profit in
that? Following in the foot steps of OPEC and other fine examples,
I suggest we form the OLEP-TRB  (the Organization of Light-bulb Eating
Persons - The Radioactive Bits). The first action of OLEP-TRB will be 
to fix the price (oops, I mean stablise the market) at $5K per bulb.

Think of the potential! Along with OLEP-GEB (Glass Envelope Bits)
and OLEP-MM (Misc Metal), we could fully utilize the ingestibiliy ot
every part of the light-bulb *while* proping up the prices!

--
Stanley Chow            InterNet: schow@BNR.CA
Bell Northern Research  UUCP:     ..!uunet!bnrgate!bqneh3!schow
(613) 763-2831
Me? Represent other people? Don't make them laugh so hard.
Newsgroups: sci.physics
From: crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass)
Subject: Re: Impure Mathematics
Organization: University of Virginia
Distribution: na
Date: Fri, 28 Aug 1992 18:18:21 GMT

In article <Aug.28.13.28.14.1992.13802@ruhets.rutgers.edu> bweiner@ruhets.rutgers.edu (Benjamin Weiner) writes:
>Scott Chase writes:
>>I agree with everything you wrote, even the parts I have omitted.  But I
>>still object to someone jumping in to censor other people's postings.
>>Maybe this person had a well-reasoned argument to make in defense of her
>>position that rape should never be the subject of humor - especially in
>>male-dominated crowds in which women are already uncomfortable.
>>So then let her make the argument in public [ ... ]
>
>Disclaimer: I never saw the original posting, nor Suzanne's comments
>[except quoted fractions] - but I think I saw the offending bit of
>"humor" a few years ago, it sounds familiar.
>
>What I wanted to say is, does Suzanne really need to make a well-
>reasoned argument that jokes about rape aren't funny?  Just sit back
>and think about it for a moment.  They're _obviously_ not funny, and
>people who can't figure that out are probably beyond hope.
>
>Given how common such offensive behavior is (not to mention the
>commonness of actual rape) I can see how someone could get fed up.
>Men in male-dominated fields can get even more isolated than most
>from what signals they are sending, so they ought to be extra
>careful.  Hence the reason I'm posting this to sci.physics.

     However, I note with interest that most of the men in my completely
     male-dominated profession are married and most of the rest of us
     are involved in a relationship with a woman.  Thus, the vast majority
     have viewed at least one woman outside our otherwise monastic existence.
     Some of us even spend more time with that woman than we do
     with our colleagues, if you can believe that.

     Getting fed up with 'Men' in general and implying such behavior
     is an appropriate response (albeit one we should be 'extra
     careful' to avoid) when a profession is male-dominated
     seems to make about as much sense as choosing to hate all women
     because one once had a bad nurse.

     And the reason I posted this is that I am tired of the insinuation
     that because we are in a male-dominated field we have to somehow
     behave differently than we do in other parts of our lives that
     are not male-dominated.  I prefer to try to behave like a human
     at all times, others prefer to be dolts.  I suspect that dolts'
     behaviors do not change outside the workplace, and I do not appreciate
     being told to walk on pins and needles because of the behavior
     of dolts any more than I appreciate the implication that men are 
     commonly rapists.

     I guess maybe I read the equality stuff too literally ...

                                 dale bass


-- 
C. R. Bass                                           crb7q@virginia.edu
Department of Mechanical and Aerospace Engineering
University of Virginia
Charlottesville, Virginia                            (804) 924-7926
From: lordSnooty@cup.portal.com (Andrew - Palfreyman)
Newsgroups: sci.physics
Subject: Re: FTL BREAKTHROUGH! NEW UNITARY DESIGN
Date: Tue, 25 Aug 92 11:12:50 PDT
Organization: The Portal System (TM)

Funny thing is, I remember someone posting this next week too.
 --------------------------------------------------------------------------
| lord snooty @the giant | Would You Like Fries With That?                 |
| poisoned electric head |              andrew_-_palfreyman@cup.portal.com |
 --------------------------------------------------------------------------
Xref: sparky sci.physics:14062 sci.environment:11053 misc.consumers:16100
From: jgd@dixie.com (John De Armond)
Newsgroups: sci.physics,sci.environment,misc.consumers
Subject: Re: Radioactivity and Superstition; was: Re: Are Your Light Bulbs Radioactive?
Date: 3 Sep 92 23:21:56 GMT
Organization: Dixie Communications Public Access.  The Mouth of the South.

jmc@SAIL.Stanford.EDU (John McCarthy) writes:

>Jym Dyer complains about the concentration, but the total possible
>exposure is surely more relevant.  If someone will supply me with
>the previously posted data about the amount of radioactivity, I'll
>try to do a calculation and decide whether to offer to eat the
>radioactive part for a reasonable payment, e.g. $10,000 for every
>day it reduces my life expectancy.  Am I allowed to encapsulate
>the active element in something that protects me from its chemical
>neighborhood?

You don't want to do it that way or you won't make anything.  Do it
for, say $10k a bulb.

The active material is typically Kr-85 which is a gas.  It is in the
STARTER of non-electronic CF bulbs.  The starter is in the plastic 
base of the bulb.  The quantity is typically 0.1 uCi or less.
My thin window pancake probe on my GM counter will not discriminate it
above background.  My NaI-based gamma spectrometer will barely see it
after several hours of counting and then only with heavy shielding.

Since Kr-85 is a noble gas which goes in and comes back out
every time you breath, at $10k a pop you could easily exceed the
net worth of Perot before you'd have to start  thinking about
risk.  What to do with all that yucky broken glass and  phosphor
though.  Can we do this as a team?

John
-- 
John De Armond, WD4OQC               |Interested in high performance mobility?  
Performance Engineering Magazine (TM) |
Marietta, Ga                         |Interested in high tech and computers? 
jgd@dixie.com                        |Write me about PE Magazine
Need Usenet public Access in Atlanta?  Write Me for info on Dixie.com.
From: barry@arnold.math.ucla.edu (Barry Merriman)
Newsgroups: sci.physics
Subject: Re: Report on Philosophies of Physicists
Date: 3 Sep 92 10:33:36 GMT
Organization: UCLA, Mathematics Department

In article <2697@news.cerf.net> mitsu@nic.cerf.net (Mitsuharu Hadeishi) writes:
> 
> 
> >What this has to do with QM is not clear to me. [B. Merriman]
> 
>         The basic issues of epistemology, etc., that are raised
> by most of the Eastern schools of philosophy and answered very
> differently from most logical positivist Western schools are exactly
> the kinds of issues raised by QM, particularly when you consider
> the measurement problem.  That is to say, if you've already gone
> into these issues in the context of Eastern philosophy, you will have
> a head start in trying to understand the philosophical problems
> associated with quantum measurement. 

That sounds good on paper. However, I must then ask: given their
conceptual headstart, why was QM developed in the west, not the east?

Perhaps the very same philosophical precepts that you  say
'favor' the eastern mind also discourage them from devolping
detailed scientific theories of nature.

--
Barry Merriman
UCLA Dept. of Math
UCLA Inst. for Fusion and Plasma Research
barry@math.ucla.edu (Internet; NeXTMail is welcome)
Newsgroups: sci.physics
From: andrew@rentec.com (Andrew Mullhaupt)
Newsgroups: sci.physics,sci.math
Subject: Re: Symmetries, groups, and categories
Date: 27 Aug 92 02:50:45 GMT
Followup-To: sci.physics
Distribution: na
Organization: Renaissance Technologies Corp., Setauket, NY.

In article <1992Aug24.151559.24464@galois.mit.edu> jbaez@zermelo.mit.edu (John C. Baez) writes:
>In article <1198@kepler1.rentec.com> andrew@rentec.com (Andrew Mullhaupt) writes:
>I've seen something on chaos in renormalization group theory in a
>mini-course I took at MIT recently... is this the sort of thing your
>last sentence refers to???  

I guess you can call analytic dynamics chaos theory. It's certainly related.
But the most interesting renormalizations are in number theory, and you
get exposed to them in the work of Mahler, Hardy, Ramanujan and Rademacher.

>What's Karmata theory?

If you have two incommensurate renormalization generators, then you can
eliminate some of the weird solutions to your asymptotics. Karamata's theorems
generally result in _slowly varying_ or _regularly varying_ asymptotics.

DeBruijn has some good stuff on this, basically the funny asymptotics are
what intermittency is all about (according to me and some other people).
Had I not joined the financial world this is what my research would have been.
Interestingly enough, the intermittency corresponds to phase transitions
in statistical mechanical language.

>>Then again the monoid action is more interesting than the monoid, but this
>>isn't news, right?

>True, and a good point.  The fact that a standard first-semester
>abstract algebra course discusses groups in detail but doesn't even
>MENTION their representations has always struck me as utterly
>villainous.  (Hence the cross-post to sci.math.)  What is the %^(ing
>point of groups other than the fact that they act as symmetries of
>something? 

Later,
Andrew Mullhaupt
Newsgroups: sci.physics