HDTenEightyP/NetNews huggingface dataset:
From: bafta@cats.ucsc.edu (Shari L Brooks)
Newsgroups: sci.physics
Subject: Re: How do you draw a straight line?
Date: 7 Oct 1992 02:19:47 GMT
Organization: University of California - Santa Cruz, CA, USA
NNTP-Posting-Host: am.ucsc.edu
Summary: my answer


Mathematically:

The shortest distance between two points in a EUclidean universe is said to
lie on the one and only line that those two points have in common.  Therefore
one needs only a chalk string and two tacks.  :)

After that we can tie the ends of the string together and draw an ellipse.

Physically:

It is much easier to draw a vertical line.  The field lines for the local
gravitaional pull of the earth are straight.  Take the chalk string and
hang a plumb on the end of it.  For thousands of years this was how buildings
were determined to stand straight.

Now the inaccuracies in the above answers will be caused by ignorable local
curvature effects.  I say ignorable because the correction terms are so small
that we can safely ignore them.  For example, deviations from the local
vertical by earth's grvitational field lines result in about as much 
inaccuracy for a straight plumb line as considering the Sun a point mass
instead of extended body will result in deviations in computing earth's 
orbit....(I admit this is a guess)

-- 
If you blow fire against the wind, take care to not get the smoke in your eyes.
      Big & Growly Dragon-monster        |       bafta@cats.ucsc.edu
     ------> shari brooks <-------       |       bafta@ucscb.ucsc.edu
                             All opinions are my own.
Newsgroups: sci.physics
From: bhv@areaplg2.corp.mot.com (Bronis Vidugiris)
Subject: Re:  Simple observation about Quantum Kitty Cats
Organization: Motorola, CCR&D, CORP, Schaumburg, IL
Date: Wed, 30 Sep 1992 19:18:11 GMT

In article <1992Sep29.062215.18619@asl.dl.nec.com> terry@aslws01.asl.dl.nec.com (Terry Bollinger) writes:

)How about the non-trivial issue in my same email -- that is, whether
)my quantum/non-quantum bullet analysis is correct or not?  Anyone?

I thought that was a pretty thought-provoking piece.  A couple of
thoughts:

1)  I think you were right on about the usefulness of talking about actual
experiments.  I was surprised at the amount philosophical differences
hindered the previous attempts at discussing QM on the net h ere.

2)  Rather than looking at information 'left behind' might it not be
just as good to look at disturbance of the bullet?  So rather than to regard
the culprit behind not being able to measure the wave function of a bullet
when light was hitting it as an 'information' problem, one could say that it
was the disturbance of the photons that made the difference.  This would also
be more quantitiative, IMO (see point 3).  Also, it would mean that Fenyman
wasn't so wrong :-) :-).

3)  Gravity doesn't seem to affect interference fringes of particles - why
should it affect the interference fringes of bullets?  It seems that someone
suitably vessed in the arcane art of QM could figure out whether gravity was
theoretically 'enough' of a disturbance or not.

4)  Has anyone done interference effects with molecules?  I know there is
a technique called 'molecular beam epitaxy' that involves creating 'beams'
of molecules.  (The technique is simple too - you just heat something up
to a low vapor pressure in a vacuum - unless of course it's more complex
than that :-)).  Anyway, there might be a way to do actual experiments with
relatively large particles such as molecules - and maybe it's been done, I
really don't know.
Newsgroups: sci.physics
Subject: Re: Society's New Contract with Scientists (draft legislation)
From: jim@netlink.cts.com (Jim Bowery)
Date: Sat, 26 Sep 92 10:42:17 PDT
Organization: NetLink Online Communications, San Diego CA

Audit:  sci.physics,JBowery,1
 
On the debate between Cameron Randale Bass and Johan Wavers:
 
In large measure, they are both correct but they both suffer from
an impossible dilemma which, happily, is a false one:
 
Johan Wevers is correct that politicians prone to porkbarrel are 
very poor judges of appropriate priorities for scientific research.
He then chooses scientists themselves as the best arbiters.
 
Cameron Randale Base is correct that if scientists themselves are
the arbiters of the funding the public grants them, their lack of
accuntability will cause them to degenerate into politicians posing 
as scientists.  He then chooses openly elected politicians as the best 
arbiters.
 
This apparent dilemma is, fortunately, false.
 
A third and optimal alternative is laid out in legislative 
language of my original message.  That alternative is to designate
all public funding to be for pure science only, under a preexisting
statutory definition of pure science, and then deligate authority to
disperse those funds to a group which has objectively demonstrated 
its grasp of the laws of nature AND public utility:
 
Inventors of royalty bearing patents.

--                    
INTERNET:  jim@netlink.cts.com (Jim Bowery)
UUCP:   ...!ryptyde!netlink!jim
NetLink Online Communications * Public Access in San Diego, CA (619) 453-1115
Newsgroups: sci.physics
From: platt@watson.ibm.com (Daniel E. Platt)
Subject: Re: Society's New Contract with Scientists (draft legislation)
Date: Mon, 28 Sep 1992 15:12:32 GMT
Disclaimer: This posting represents the poster's views, not necessarily those of IBM
Organization: IBM T.J. Watson Research Center

In article <71yPRB4w165w@netlink.cts.com>, jim@netlink.cts.com (Jim Bowery) writes:
|> Audit:  sci.physics,JBowery,1
|>  
|> On the debate between Cameron Randale Bass and Johan Wavers:
|>  
|> In large measure, they are both correct but they both suffer from
|> an impossible dilemma which, happily, is a false one:
|>  
|> Johan Wevers is correct that politicians prone to porkbarrel are 
|> very poor judges of appropriate priorities for scientific research.
|> He then chooses scientists themselves as the best arbiters.
|>  
|> Cameron Randale Base is correct that if scientists themselves are
|> the arbiters of the funding the public grants them, their lack of
|> accuntability will cause them to degenerate into politicians posing 
|> as scientists.  He then chooses openly elected politicians as the best 
|> arbiters.
|>  
|> This apparent dilemma is, fortunately, false.
|>  
|> A third and optimal alternative is laid out in legislative 
|> language of my original message.  That alternative is to designate
|> all public funding to be for pure science only, under a preexisting
|> statutory definition of pure science, and then deligate authority to
|> disperse those funds to a group which has objectively demonstrated 
|> its grasp of the laws of nature AND public utility:
|>  
|> Inventors of royalty bearing patents.

Actually, this is also not a good idea.  Funding decisions should be made
by a disinterested (not uninterested) population.  Inventors are not
disinterested.

Dan
From: jac@ds8.scri.fsu.edu (Jim Carr)
Newsgroups: sci.physics
Subject: Re: Question about electron spin
Date: 27 Sep 92 18:52:58 GMT
Reply-To: jac@ds8.scri.fsu.edu (Jim Carr)
Organization: SCRI, Florida State University

In article <1992Sep27.185539.594@prim> prim!dave@germany.eu.net (Dave Griffiths) writes:
>I've just been reading Roger Penrose's explanation in the Emperor's New Mind
>of the EPR experiment. In this he claims that it is possible to measure the
>spin of an electron in three different directions at 120 degrees to each
>other and obtain the result YES, the spin of the electron is aligned in
>that direction for each measurement. Surely this is incorrect? He has already

Nope.  It is correct. 

>shown that if you measure the spin in one direction and get the answer YES,
>then there is a probability of (1 + cos 120)/2 = 1/4 that a measurement at
>120 degrees to this will also give the answer YES. Fine. But surely, with 
>the wave function having collapsed, it's not possible for three measurements 
>at 120 degrees to each other _all_ to give YES?

Why not?  The wavefunction was "collapsed" in the original direction 
before you ran it through the first 120-degree analyzer.  The chance of 
getting three YES answers from the system described is just 1/4 * 1/4 * 
1/4 = 1/64 = 1.56%.  

The answer is identical to the answer you get for three Polaroid sheets 
laid at 120-degree angles on top of an sheet that defines the original 
polarization.  Surely you have seen (or done, find some friends with 
Polaroid sunglasses) the experiment where you have crossed (90 degree) 
polarizers and then insert one between them at 45 degrees and see it 
go from black to (dim) light.  Same thing with electrons. 

>If it is possible, has such a result ever been experimentally confirmed?
>
>Please say no.

Sorry, the answer is yes.  I know people who do this sort of thing all 
the time when doing experiments with polarized beams.  

Is your brain numb yet? 

--
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)
Newsgroups: sci.physics
From: jlg@cochiti.lanl.gov (Jim Giles)
Subject: Re: Simple observation about Quantum Kitty Cats
Organization: Los Alamos National Laboratory
Date: Wed, 30 Sep 1992 17:12:47 GMT

In article <297@mtnmath.UUCP>, paul@mtnmath.UUCP (Paul Budnik) writes:
|> In article <1992Sep28.134825.29472@oracorp.com>, daryl@oracorp.com (Daryl McCullough) writes:
|> > 
|> > 1. QM, with its quaint axioms
|> > about measurement processes is an enormously successful theory; there
|> > are absolutely no hints to the limitations to its applicability.
|> 
|> That depends on what you consider a hint. Quantum mechanics predicts that
|> by changing the setting on an instrument we can influence what happens
|> arbitrarily large distances away.  [...]

No.  QM predicts that changing the setting on a local instrument will
influence what happens locally in such a way that these local occurrences
correlate differently with distant events.

|. [...]                                    There has never been a shred of
|> experimental evidence supporting such action at a distance.  [...]

Since no *action* at a distance is predicted by QM, there is no
problem.  Only *correlation* at a distance is predicted.  Such
correlation is quite commonplace in non-QM contexts using hidden 
variables.  The QM difference is that hidden variables have been
shown *not* to be involved.

-- 
J. Giles
From: rlp@bsu-cs.bsu.edu (Ralph L. Place)
Newsgroups: sci.physics
Subject: Joke
Date: 1 Oct 92 18:37:16 GMT
Organization: CS Dept, Ball St U, Muncie, Indiana

There may be a problem with the cross between an elephant and a grape,
that is, neither are vectors.  Now, a mosquito is, and the flea.  So
    mosquito x flea = |mosquito| |flea| sin(theta)
is valid.

:-)

R.Place
Dept of CS
Ball State University
Muncie, IN 47306
rlp@bsu-cs.bsu.edu

Newsgroups: sci.physics
From: daryl@oracorp.com (Daryl McCullough)
Subject: Re: Defining local, causal etc., was: Hidden variable theories
Organization: ORA Corporation
Date: Fri, 25 Sep 1992 15:04:01 GMT

In article <1992Sep24.131427.6543@oracorp.com>, From:
daryl@oracorp.com (Daryl McCullough) writes: (in response to Robert
Firth)

> That's what I mean by saying that what quantum mechanics says is
> unclear. You contradict me, call me confused, and then make the same
> point that I was making (in a much more long-winded way).

>[and other rudeness]

I apologize for the tone of my response. Your article was not
long-winded, it was very thoughtful and informative. I must have been
in an ornery mood that day.

Daryl McCullough
ORA Corp.
Ithaca, NY
Newsgroups: sci.physics
From: raicu@netcom.com (Eugen Raicu)
Subject: Newton's 3rd law and relativity
Organization: Netcom - Online Communication Services  (408 241-9760 guest) 
Date: Thu, 1 Oct 1992 04:28:58 GMT

Is there anything in relativity that, in the classical limit,
becomes Newton's 3rd law?
-- 
Eugen Raicu
raicu@netcom.com
Newsgroups: sci.physics
From: micha@ecrc.de (Micha Meier)
Subject: Re: How do you draw a straight line?
Reply-To: micha@ecrc.de
Organization: European Computer-Industry Research Centre
Date: Mon, 5 Oct 1992 15:42:11 GMT

In article 24242@access.usask.ca, choy@skorpio.usask.ca (I am a terminator.) writes:
>How do you know that the line you draw is really straight? What
>defines straightness?

This is something I've been wondering about since a long time. Although we can
make a circle as precise as we want, I think we cannot make a really
precise straight line - every straight line is made from another one or from a tool
that has been made using some older straight lines - so it all comes down to
copying a line that has been made thousands years ago. Although we have precise
instruments and tools, we can only make better and better lines (so that eventually
the error is less than an atom, and we are there), but IMHO there is no
process to create a straight line directly. Or is it?

--Micha
---
Micha Meier			------------------------------------------------
ECRC, Arabellastr. 17		The opinions expressed above are private
D-8000 Munich 81		and may not reflect those of my employer.
micha@ecrc.de, Tel. +49-89-92699-108, Fax  +49-89-92699-170
From: mcirvin@husc8.harvard.edu (Mcirvin)
Newsgroups: sci.physics
Subject: Re: black holes & thermodynamics
Date: 5 Oct 92 02:17:59 GMT

00jcbenson@bsu-ucs.uucp writes:

>It seems to me that a Black Hole is an object which orders the universe.  It 
>brings matter together into a point.  Now the Law of Thermodynamics concerning
>Chaos seems to suggest that the universe tends to bring down rather than to
>order itself.  So, my question is, why can a Black Hole exist if it continually
>orders the universe instead of breaking down?  

The key is not to take too seriously the identification of entropy with
"disorder".  Disorder is a term that can be interpreted to mean all kinds
of things, whereas entropy has a fairly specific meaning.  It's the entropy
of the universe that doesn't decrease, and a black hole's entropy increases
as it grows; though I don't understand this completely, the entropy is
apparently proportional to the area of the event horizon, so the entropy
goes *up* as matter goes in. 

A somewhat more precise definition of the entropy of a system is that it
is proportional to the logarithm of the number of microscopic states of
the system that are macroscopically indistinguishable.  Since a black hole
renders many states of its interior completely indistinguishable (you can't
see in), it seems reasonable to regard larger black holes as having more
entropy.

Black holes can shrink too, by Hawking radiation, and then the entropy of
the black hole is very slowly shed in the form of thermal photons.  One way
to think about this is to think of the black hole as a device that converts
anything that falls into it (eventually) into thermal photons, with a
corresponding increase in entropy.  

-- 
Matt McIrvin, posting nonsense again
From: bhoughto@sedona.intel.com (Blair P. Houghton)
Newsgroups: sci.physics
Subject: Re: Quantum Nights 1
Date: 5 Oct 92 23:35:35 GMT
Organization: Intel Corp., Chandler, Arizona

In article <1aib0hINNlp0@agate.berkeley.edu> ted@physics.Berkeley.EDU (Emory F. Bunn) writes:
>"photon picture".  After all, either the charge IS emitting photons
>or it ISN'T, right?  Wrong.  I eventually learned enough physics to 
>decide that everything was OK in the photon picture too, but if I
>tried to explain why, I'd screw it up.  I'll leave that job to
>someone else.

Someone else...

				--Blair
				  "Anyone?  Anyone?  Bueller?"
Newsgroups: sci.physics
From: jbaez@riesz.mit.edu (John C. Baez)
Subject: Re: Black hole + anti-Black hole = ?
Organization: MIT Department of Mathematics, Cambridge, MA
Date: Wed, 30 Sep 92 01:31:51 GMT

In article <80722@ut-emx.uucp> johncobb@ut-emx.cc.utexas.edu (John W. Cobb) writes:

>Most (All that I have ever seen) "no-hair" theorems are proved for classical
>systems. What about quantum systems? If a true quantum description of Hawking
>radiation (not just a semi-classical estimate) is finally worked out, is
>it not possible for it to depend on "the hair". for example, if a proton/
>anti-proton pair is created out of the curvature field just inside the horizon,
>will both the proton and anti-proton have exactly the same probability to
>tunnel beyond the horizon? Might not these probabilities be affected by the
>overall baryon number of the black-hole. Perhaps this is a way to restore
>baryon conservation in collapse situations --- then again, black holes may
>not respect baryon numbers, even in a complete quantum description.

A couple of weeks ago I posted a reference to an excellent expository
paper on this subject.  Unfortunately I no longer have the reference on
me.  Maybe someone can mail it to John Cobb - this reference is what
contained the business about "if you throw an encyclopedia into a black
hole, can you recover the information from the Hawking radiation
emitted?"... leading to many jokes here on sci.physics.  The paper
is available electronically from hepth, the high-energy physics
preprint service.  

In any event, at least in toy models quantum black holes can have
hair.  In 4 dimensions quantum gravity is too hard for us to know yet,
but people who have taken the trouble to learn string theory have
developed a lot of expertise in 2-dimensional physics, and in particular,
one can supposedly exactly solve the quantum black hole in 2 dimensions
and look for hair.  I.e., look for more quantum numbers.  They find
them, so quantum hair is a hot topic.  As you point out, this relies on
a true quantum description of the black hole, not a semiclassical
approximation in which the gravity field is treated classically and the
electrectromagnetic and other fields are treated quantum-mechanically.
(Hawking makes yet another approximation, treating the shrinking of 
the black hole due to the radiation adiabatically, i.e., not studying
the effect of the shrinking on the radiation in detail.)  

So there is some room for hope that a true quantum description will
restore baryon number (or other better quantum numbers, like lepton
number) conservation.  However, the author of this review paper gives
reasons why he thinks quantum hair will not save the day.  They are nice
but hand-wavy arguments and I am a bit too tired now to recall and
explain them.

In any event, I would think the key thing in this business would be
to see if FOUR-dimensional black holes can have hair when treated
quantum mechanically.  I'm not asking for much here - only a fully
working theory of quantum gravity.  :-)  Until we get one I don't
see how to study these questions with any assurance of being right.
Experiment is out, alas.




Newsgroups: sci.physics
From: stone@cwis.unomaha.edu (Travis Stone)
Subject: Re: Mattel Protest
Keywords: So What?
Organization: University of Nebraska at Omaha
Date: Mon, 5 Oct 1992 12:59:20 GMT


So Mattel is going to market a dollie that says
"Math class is tough!"---so what?  People have
been bitching about math classes since the dawn
of time---boys and girls alike---so obviously
the vast majority of people out there MUST agree
with this sentiment; all Mattel is doing is having
their little plastic pals voice what is undoubtedly
on every child's mind.  The point is, EVERYONE IS
ALREADY CONVINCED OF IT, SO WHO CARES IF A TOY
REPEATS IT?  If a child is going to take a liking
to math, then he/she/it won't give a tinker's
damn what some stupid toy has to say about it.

Besides, the way math is taught in this country
(especially at the grade-school level), maybe it's
not such a bad idea to prep the kids so they know
what an uphill slog it will be---and just think:
Mattel may be doing the nation's kiddies a service
by protecting their fragile self-esteem.

Billy: "Hi, Johnny! Hey, didja getcher report card?"
Johnny: "Yeah. I dint do too good, 'specially in Math.."
Billy: "Yeah? Too bad...Hey, I got a B-plus! Not bad, huh?"
Johnny: "Yeah..Way cool, Billy...I only got a D-plus, though."
Billy: "Uh-huh--Well, better luck next time, Big J."
Johnny: "Aww...I ain't worried about it, Billy...after all,
         even my sister's Barbie Doll says that math is tough..."

See? A little good can come out of every dark situation, nicht?...


T.R. Stone
University of Nebraska-Omaha
Where, yes, as you might have guessed, I'm doing
Grad work in Applied Math...
From: pad@galaxy.nsc.com (Paul Denny x8349)
Newsgroups: sci.physics
Subject: Re: Measuring Q
Keywords: FTL Communications Experiment
Date: 28 Sep 92 20:40:18 GMT
Organization: National Semiconductor, Santa Clara

In article <4350@cruzio.santa-cruz.ca.us>, snarfy@cruzio.santa-cruz.ca.us writes:
> 
> 
>   In message-ID: <1992Sep23.001937.23567@voder.nsc.com>(Paul Denny) writes:
> 
>    What  is  "w"?   If  it  takes  an  infinitely  long time to measure this
>    quantity and I get paid by the hour  it  sounds  like  a  very  expensive
>    proposition . I hope you've looked into the alternatives :

It is the usual electronics notation for angular frequency in radians.seconds^-1
and is simply 2*pi*frequency.

> 
>    MY physics book gives me the following formulas for Q:
> 
>    Q=Xl/R  (Xl = inductive reactance)

	Xl=2*pi*f*L  (f=frequency = need to know frequency to calculate Q)

> 
>    Q=Px/Pr (Px = reactive power , Pr = real power)

	Px and Pr are averages over one period of the fundamental
	frequency = need to know frequency 

> 
>    Q=El/Er (El = voltage accross the inductance  Er  =  voltage  across  the
>             resistance)
	
	El and Er are averages over one period of the fundamental
	frequency = need to know frequency

> 
>    Q=Fr/BW (Fr = Resonant frequency  , BW = bandwidth)

	Fr is frequency = need to know frequency

> 
>    Q=Il/Ir  (Il  =  current  through  the inductor , Ir = current through the
>              resistor)

	Il and Ir are averages over one period of the fundamental
	frequency = need to know frequency

> 
>     > How are you measuring instananeous changes in Q ?

I note in a later post you concede the point that you can't measure frequency
instantaneously so I hope from the above you can see that your theory that
Q changes instantaneously is meaningless and even if it were true you would
not be able to transmit information by this technique.

 - Paul

P.S. There are more definitions of Q than those we've covered - if you look at
any of them the above will apply - this is no surprise as you are just looking 
at alternative ways to measure the same thing.
Newsgroups: sci.physics