HDTenEightyP/NetNews huggingface dataset:
From: frank@rover.uchicago.edu (Frank - Hardware Hacker - Borger)
Subject: Re: Eating habits; was: Radioactivity and Superstition;
News-Software: VAX/VMS VNEWS 1.41    
Reply-To: frank@rover.uchicago.edu
Organization: Joint Center for Radiation Therapy
Date: Tue, 8 Sep 1992 15:22:00 GMT

In article <1992Sep8.125301.13874@sei.cmu.edu>, firth@sei.cmu.edu (Robert Firth) writes...
>your comment prompts the thought that, thanks to the population
>explosion, the largest source of radioactivity on the planet is
>probably humans.
> 
	No, natural background is about 0.1 rem, (old units, or 1mSv new ones.)
	Typical human exposure is about 0.1 rem
	Latest data indicates Radon may contribute about 0.2 rem.

	Average cigarette smokers receive about 8 rem/year.

   Frank R. Borger - Physicist    __       Internet:  Frank@rover.uchicago.edu
Michael Reese - Univ. of Chicago |___      Phone : 312-791-8075 fax : 567-7455
  Center for Radiation Therapy   | |_) _   
    2929 South Ellis Avenue        | \|_)  Dear son, don't come home and all is
    Chicago, Illinois 60616           |_)  forgiven. - Personal ad.
Newsgroups: sci.physics
From: jbaez@riesz.mit.edu (John C. Baez)
Subject: Re: How old is the universe?
Organization: MIT Department of Mathematics, Cambridge, MA
Distribution: na
Date: Sat, 12 Sep 92 19:39:22 GMT

SICHASE@CSA2.LBL.GOV (Scott I. Chase) writes:
>In article <1992Sep12.071024.11573@galois.mit.edu>, jbaez@riesz.mit.edu 
>(John C. Baez) writes...

>Surely you're joking, Mr. Sutherland!  The "center"?  Everyone knows
>that it's in Boston!  

>I think you meant to say "Cambridge," not "Boston."  We all know that the 
>center of the Universe is a couple of miles down the road from that little
>red schoolhouse, don't we?  

I was trying to be modest and you've gone and blown it.  Yes, for most
purposes Boston is a good approximation to the center of the universe,
but if you look in the CRC Handbook you'll see that it is exactly at
149A Bishop Allen Dr., Cambridge.  (Can't wait to get back!)

You may wonder how the center was determined.  Very simple: go there,
look around, and you will notice that the farther away objects are from that 
spot, the smaller they appear!


.
From: sgooch@uts.amdahl.com (Shelley H. Gooch)
Newsgroups: sci.physics
Subject: Re: E=mc2?
Summary: Single sentence
Date: 7 Sep 92 00:46:17 GMT
Organization: Amdahl Corporation, Sunnyvale CA

Having examined Einstein's original letter in the Smithsonian, I was
amazed to see that such an historically monumental letter consisted of
only one, or at the most 2 sentences.  It said only that he thought
that work toward developing an atomic bomb was likely to be fruitful,
and was signed A. Einstein.  Kind of like Reagan's one sentence memo
(executive order) giving the cia the right to conduct covert
operations inside the states and properties of the United States.

It's amazing how short and sweet these things can be.  Unlike...


-- 

ShellEy (not Shelly)

--------------------------------------------------
Shelley H. Gooch
sgooch@uts.amdahl.com
(408) 746-7652
M/S 316 O-16/Room 3537
From: matt@physics.berkeley.edu (Matt Austern)
Newsgroups: sci.physics
Subject: Re: Did electric/magnetic symmetry "break"?
Date: 10 Sep 92 16:53:05 GMT
	<1992Sep7.214235.24769@galois.mit.edu>
	<1992Sep9.204019.17182@asl.dl.nec.com> <mcirvin.716088539@husc8>
Reply-To: matt@physics.berkeley.edu
Organization: Lawrence Berkeley Laboratory (Theoretical Physics Group)
NNTP-Posting-Host: physics.berkeley.edu
In-reply-to: mcirvin@husc8.harvard.edu's message of 10 Sep 92 01:28:59 GMT

In article <mcirvin.716088539@husc8> mcirvin@husc8.harvard.edu (Mcirvin) writes:

> To express the potentials
> in such a way that electric and magnetic charge come in symmetrically
> in the Lagrangian, my guess is that you'd have to somehow put in
> more degrees of freedom: define a "dual potential" whose 4-curl
> would be the dual field strength tensor, and then put in constraints
> so that everything stays consistent, or some such thing.

Actually, I think it's pretty straightforward.  The gauge group for
electromagnetism is U(1).  From Noether's theorem you find that there
is a single conserved charge, which you may as well call the electric
charge.  (Although, as Jackson points out, this is a matter of
convention.)

If you want to treat electric and magnetic charge symmetrically, you
need to expand the gauge group to something with two generators---or,
in more physical terms, you need two vector potentials.  I imagine
that the gauge group would be U(1)xU(1).
--
Matthew Austern                   Just keep yelling until you attract a
(510) 644-2618                    crowd, then a constituency, a movement, a
austern@lbl.bitnet                faction, an army!  If you don't have any
matt@physics.berkeley.edu         solutions, become a part of the problem!
Newsgroups: sci.physics
From: phfrom@nyx.uni-konstanz.de (Hartmut Frommert)
Subject: Re: What do we know about choice of groups?
Organization: Dept. of Physics, University of Constance
Date: Fri, 11 Sep 1992 13:18:40 GMT

matmcinn@nuscc.nus.sg (Mcinnes B T (Dr)) writes:

>Suppose that the standard theory is right, and that the gauge group of
>the world is "SU3xSU2xU1"  [actually S[ U2xU3 ] of course]. Then we will
>have to understand why this particular group was chosen from infinitely
>many others. The same problem arises, albeit less urgently, if GUTs are
>correct: why SO[10]  [actually Spin[10] of course]  rather than SO[110]
>?
>What ideas have been proposed to solve this problem? 

Don't know and don't want to mention all ideas of course, but 
* the "321" theory is the *minimal* one required for a description of the
  experimental facts (i.e. particle spectrum: The particles observed show
  that there is a "321" inner gauge symmetry group, the corresponding
  gauge bosons have been observed, and the fermions can be classified as
  members of the corresponding reps, etc.)
* there is no experimental/observational evidence for any, nor for a certain
  GUT besides some correlation of the coupling constants and a rather good
  b-quark mass
so that the only physical requirement is that
* the SU3xSU2xU1 is contained in the group considered, and there must be a
  mechanism (generalized [?] Higgs) which condenses out that group as the
  one relevant at the low energies in present day accelerators.

So in principle you may start with an arbitrary supergroup of the "321"
(observing some QFT constraints), inhibit suited symmetry breaking to the 
321 (for example by suited Higgs mechanism(s)) which make that gauge bosons
supermassive that were not observed to now. Then figure out specific effects
(e.g. proton decay) where the theory differs from SM, and look at the 
experimental data: in most cases this gives some limitations to the ranges 
of some parameters, maybe some theory is even ruled out. But (without 
superstring theory or similar things) you will still have many possibilities
for modelling particle symmetries.
--
 Hartmut Frommert                 <phfrom@nyx.uni-konstanz.de>
 Dept. of Physics, Univ of Constance, P.O.Box 55 60, D-W-7750 Konstanz, Germany
                                            -- Eat whale killers, not whales --
Xref: sparky sci.physics:14282 alt.sex:28670
From: prem@prem.lbl.gov (Shirdi R. Prem)
Newsgroups: sci.physics,alt.sex
Subject: Re: BAROMETERS (was Re: Subject?)
Date: 8 Sep 92 19:18:14 GMT
Reply-To: prem@prem.lbl.gov (Shirdi R. Prem)
Distribution: na
Organization: Lawrence Berkeley Laboratory
NNTP-Posting-Host: prem.lbl.gov

In article <1992Sep4.165932.25043@wixer.cactus.org> purp@wixer.cactus.org (Jim Meyer) writes:
>In article <ZOWIE.92Sep1122151@daedalus.stanford.edu> zowie@banneker.stanford.edu writes:
 >>You are taken to a large, impressive-looking office building.  You may
 >>wander the building and its environs at will <etc. etc.> You are given
 >>an accurate barometer.  Your task is to determine the height of the
 >>building.
 >>
 >>Name at least six ways to accomplish this task. [before breakfast! ;-]
 >
 >Ok, here goes:
 >   :
 >   :
 >   :
 >Good 'nuff?
 >

	Er....You missed one......

	Go to the caretaker of the building. Offer to perform kinky sexual
	favours with the barometer, in exchange for information about the
	height of the building.
From: jac@ds8.scri.fsu.edu (Jim Carr)
Newsgroups: sci.physics
Subject: Re: Uncertainty Principle
Date: 5 Sep 92 02:17:13 GMT
Reply-To: jac@ds8.scri.fsu.edu (Jim Carr)
Organization: SCRI, Florida State University

In article <5273@tuegate.tue.nl> johan@blade.stack.urc.tue.nl (Johan Wevers) writes:
>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

but it does not require the wave formalism for its derivation, since 
the non-commutation of conjugate variables also appeared in the 
Heisenberg matrix method (to his puzzlement till this got sorted 
out in one of Dirac's nice papers). 

>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.    ....

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

Exactly.  And conjugate variables do not commute. 

The mathematics speaks.  The various explanations involving scattering 
wavelengths and measurement and so forth are pedagogical tools.  They 
are not wrong (since the results follow from QM) but they are not 
necessary parts of an explanation. 

--
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: mfterman@dae.Princeton.EDU (Mutant for Hire)
Subject: Re: Hidden variable theories, was: Uncertainty Princi
Reply-To: mfterman@phoenix.princeton.edu (Mutant for Hire)
Organization: Mutant for Hire, Inc.
Date: Thu, 10 Sep 1992 22:31:19 GMT

In article <BuDu1G.4JB@usenet.ucs.indiana.edu>, foxd@silver.ucs.indiana.edu (daniel fox) writes:
>What has bothered me about the "killing your grandfather time travel paradox"
>is that it seems to assume a Newtonian view of the universe.  I would think
>that if such an experiment were attempted (by using massive rotating cylinders
>or whatever) one would find that quantum mechanics would have to be used to
>figure out what happened.

In a lecture on closed timelike loops, someone pointed out that if you
had some wormholes that allowed one to go backwards in time, one could
have a ball fly between two wormholes, or fly up, get knocked into a
wormhole by its future self, fly out and knock its past self into a
wormhole, then fly on, and all sorts of higher order possibilities. Of
course, you could try to treat these as difference possibilities in QM
and let interference sort out what is actually going on. Granted a
more general case like going back in time to kill your grandfather
isn't so simple. Since closed timelike loops are neither [un]provable
or seen anywhere, I'm not going to sweat the issue.

-- 
    Martin Terman, Mutant for Hire, Mad Scientist, Priest of Shub-Internet
    Disclaimer: Nobody else takes me seriously, why should you be the first?
mfterman@phoenix.princeton.edu mfterman@pucc.bitnet terman@pupgga.princeton.edu
"Sig quotes are like bumper stickers, only without the same sense of relevance"
Newsgroups: sci.physics,sci.math
From: pratt@Sunburn.Stanford.EDU (Vaughan R. Pratt)
Subject: Re: Report on Philosophies of Physicists
Organization: Computer Science Department,  Stanford University.
Date: Mon, 14 Sep 1992 00:14:12 GMT

In article <1992Sep13.221834.5022@infodev.cam.ac.uk> gjm11@cus.cam.ac.uk (G.J. McCaughan) writes:
>Vaughan Pratt claims that set theory was always used foundationally,
>citing the use of set theory in general topology as proof.
>
>This sort of "foundational" use is Very Different from the idea of
>set theory as a foundation for all of mathematics.

Yes.  I cited some 19th century mathematicians who talked about set
theory as giving them a foundations.  Whatever they meant by that,
that's what I meant when I said that mathematicians started using set
theory because they found it to be a workable foundations.  It was
Torkel Franzen who brought up your latter meaning.  I neither deny nor
affirm that the latter meaning is what the cited parties intended, only
that I meant nothing more than they.

-- 
======================================================| God found the positive
Vaughan Pratt   pratt@cs.Stanford.EDU   415-494-2545  | integers, zero was
======================================================| there when He arrived.
From: sichase@csa2.lbl.gov (SCOTT I CHASE)
Newsgroups: sci.physics
Subject: Re: 137, was: Did electric/magnetic symmetry "break"?
Date: 12 Sep 92 18:58:15 GMT
Organization: Lawrence Berkeley Laboratory - Berkeley, CA, USA
Distribution: na
Reply-To: sichase@csa2.lbl.gov
NNTP-Posting-Host: 128.3.254.197
News-Software: VAX/VMS VNEWS 1.3-4   

In article <82607@bcsaic.boeing.com>, davidk@bcsaic.boeing.com (Dave Kerlick) writes...
>(2 / alpha - 1) degrees Celsius.  It got published, to much merriment.
                 ^^^^^^^^^^^^^^^
Kelvin.

-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
From: thomas@trane.UUCP (Thomas Driemeyer)
Newsgroups: sci.physics
Subject: books on spectrography and surface analysis?
Date: 7 Sep 92 15:49:57 GMT
Distribution: na
Organization: Aurora Systems, Santa Clara, CA

I need to become an instant expert on spectrography and molecular surface
analysis. Are there any good books that I can understand without a physics
or chemistry degree?

Thanks for any pointers.

Thomas

--
Thomas Driemeyer         thomas%trane@pacbell.com           voice: 408 988 2000
			thomas@bitrot.in-berlin.de
From: johan@blade.stack.urc.tue.nl (Johan Wevers)
Newsgroups: sci.physics
Subject: Re: Hidden variable theories, was: Uncertainty Princi
Date: 11 Sep 92 09:09:22 GMT

In article <267@mtnmath.UUCP> paul@mtnmath.UUCP (Paul Budnik) writes:

>The Schrodinger equation is local. Quantum mechanics plus the collapse
>postulate is a nonlocal theory that predicts nonlocal experimentally
>detectable effects.  Any theory of any form that is consistent with quantum
>mechanics must also be nonlocal. 

I've always thought that the Schr\"odinger equation was non-local because
it contains only a first time derivate, just as the diffusion equation.
The only mathematical difference between the schr\"odinger equation and
the diffusion equation was (I thought) the complex numbers in the S.E..

Now who is wrong ?

******************************************************************** 
* 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: earl@netcom.com (Earl Vickers)
Subject: Why Do Mirrors Reverse Left/Right and Not Up/Down?
Date: Sat, 05 Sep 92 04:03:55 GMT
Organization: Netcom - Online Communication Services (408 241-9760 guest)
Distribution: na

Yes, I read the FAQ already, but the answer it gave ("Mirrors don't
reverse Left/Right") was too easy. The question should be, Why do
mirrors *appear* to reverse Left/Right, and not Up/Down?
If I have a mole on my left cheek, why does the guy in the mirror
have a mole on *his* *right* cheek?

I think there are a couple of answers, having more to do with
psychology than with physics, but I'll post them here anyway. :-)
First of all, people tend to be more or less symmetrical about a
vertical axis, but not about a horizontal one. Secondly, if a person
were to rotate and walk behind a mirror, he/she would be more likely
to rotate about a vertical axis than to flip upside down.
Therefore, when you see the "person behind the mirror," you think,
it's like I walked behind the mirror, only now my mole is on the other
cheek, therefore it's flipped left/right. But if we were symmetrical
about a horizontal axis, you might think, It's like I flipped upside down
to get behind the mirror - the guy in the mirror looks just like me,
except that if I flipped upside down to get behind the mirror, the mole
on my top cheek (or whatever) would be on the bottom, but this guy's
mole is on the top. (Left and right, however, appear un-flipped.)

Sorry if this isn't the clearest explanation, but it's a hard thing to put
into words. But simply saying that "mirrors don't reverse left and right"
ignores the real question, which is, Why is it so stubbornly obvious
that they do?

Please give me a minor footnote in the history of science for finally clearing
this matter up.

-- 
Earl Vickers		earl@netcom.com
From: ric@hpspdla.spd.HP.COM (Ric Peregrino)
Date: Tue, 15 Sep 1992 20:46:56 GMT
Subject: Re: Rotating Bucket of Water in a Gravitation Field...Part #2
Organization: HP Stanford Park - Palo Alto, CA
Newsgroups: sci.physics


Hmmm...

What if you imposed a condition for the cosmic matter distribution
in the large such that the effect of spinning the Earth was exactly
equal to that of spinning the universe around the Earth? Obviously
my one flashlight universe would have to be spun much faster than
the Earth was to give the same deformation of the waters surface.
Too much mass would make the opposite case, but wouldn't equal
effect give a condition for the mass distribution? Perhaps this
"boundary condition" leads to some closed form metric solution.

See pg. 102 of Einstein's "The Meaning of Relativity".

--------------------------------------------------------------------------
Ric Peregrino     c/o Hewlett Packard Co.        I represent only myself
ric@spd.hp.com    1501 Page Mill Rd. Bldg. 5M    I may be wrong, maybe not
415-857-7526      Palo Alto, CA 94304            Do DC photons exist?
--------------------------------------------------------------------------
Newsgroups: sci.physics
From: barry@arnold.math.ucla.edu (Barry Merriman)
Subject: Re: Uncertainty Principle
Organization: UCLA, Mathematics Department
Date: Sat, 5 Sep 92 22:39:23 GMT

In article <5400@dove.nist.gov> gilligan@bldrdoc.gov (Jonathan M. Gilligan)  
writes:
> In article <1992Sep4.170847.235@prim> prim!dave@germany.eu.net (Dave  
Griffiths) writes:
> >
> >I just read (Stephen Hawking) a nice explanation of the Uncertainty  
Principle:
> 
> Karl Popper points out that this argument fails to explain why we
> can't first...

> His point was not to show any inconsistency in quantum
> mechanics, but to show the shortcomings of thinking in terms of
> thought experiments.  


Perhaps Karl Popper should study theories of thinking, rather than 
physics. The purpose of such simple thought experiments is not to 
embody the exact uncertainty principle within a thought experiment. 
Rather, the point is to fit the concept naturally into one's own 
conceptual framework, so that it can be mentally manipulated and applied
with ease. 

I.e., these minimal conceptions allow one to use the 
tool readily. Once you've discovered a use, then you can go back 
and check that you didn't missapply. The purpose of these minimal
conceptions is _creative thought_, not _rigorous thought_.

I think Popper should not be telling physicists how to think 
about things, seeing as he is a philosopher, and has not done
any creative work in theoretical physics 
(or thinking skills, apparently)

--
Barry Merriman
UCLA Dept. of Math
UCLA Inst. for Fusion and Plasma Research
barry@math.ucla.edu (Internet; NeXTMail is welcome)
From: snyder@henry.ece.cmu.edu (John Snyder)
Newsgroups: sci.physics
Subject: Re: Wave/particle duality
Keywords: photon,particle,dual slits,interference,quantum waves
Date: 14 Sep 92 20:18:36 GMT
Organization: Physics Department, Carnegie Mellon University

In article <1992Sep14.032341.19533@asl.dl.nec.com> terry@aslws01.asl.dl.nec.com (Terry Bollinger) writes:
>In article <BuJEy1.Gz5@nntp-sc.Intel.COM>
>bhoughto@sedona.intel.com (Blair P. Houghton) writes:
>
>> Read Feynman's Lectures on Physics, chapters 1-3 of volume III, carefully,
>> and if you start thinking of particles as waves go back and read them again.
>
>Dr. Feynman was even more explicit in stating that photons and electrons are
>particles in "QED: The Strange Theory of Light and Matter."  In that delight-
>ful little easy-reading book he begins by pointing out that if human eyes
>were about 10 times more sensitive the classic debate about whether photons
>were particles or waves never would have occurred.  In dim light everyone
>would have been able to SEE individual photons banging on their retinas as
>point-like flashes.
>
>(One wonders how the particle-wave debate would have unfolded had it first
>been undertaken by wise old owls instead of half-blind humans...)
>


Now I'm curious...Do owls really see in point-like flashes in low light?
Does anyone know?

John
snyder@henry.ece.cmu.edu
Xref: sparky sci.physics:14637 sci.math:11427
From: kmurali2@uoft02.utoledo.edu
Newsgroups: sci.image.processing
Subject: Sub-band coding of HDTV Images Help
Date: 8 Sep 92 22:17:40 EST
Organization: University of Toledo, Computer Services

Hi Netters,

	I am plannning to do my MS thesis in Sub-band coding of HDTV Images. 
Are there any easily undestanding (w/o much of abstract Mathematics) tehnical 
papers or text books avialable ? Is there any technique that can be used to 
reduce the bit/pixels. Any help would be appreciated.

thank you

murali. k 
Newsgroups: sci.image.processing
From: dickw@IASTATE.EDU (Richard Wallingford)
Subject: Re: ccd camera
Keywords: CCD cameras, radiometric calibration, flat field
Reply-To: dickw@IASTATE.EDU (Richard Wallingford)
Organization: Iowa State University
Date: Tue, 8 Sep 1992 16:01:41 GMT

In article <3093@ariel.its.unimelb.EDU.AU>, mark@sunrise.sli.unimelb.edu.au
(Mark Shortis) writes:
> Would anyone like to comment on the problem of calibrating the
> radiometry of individual pixels in a CCD array?  
> 
> Essentially the problem is that for applications which require accurate 
> radiometry (ie accurate grey levels are needed) the response of each pixel 
> becomes important.
> 
> This is the classic issue of "flat fielding".  That is, if you supply a
> perfectly uniform input, the response of every pixel can be calibrated.
> Do this at two light levels and an offset and gain for each pixel can be
> computed.

An alternative approach is to produce a calibration image for each
exposure which will not only remove the effects of CCD response
but nonuniform illumination.   

In my case, I have to deal with nonuniformities in the light box
when digitizing x-ray radiographs.  Thus, for each acquisition
session, I digitize the lightbox with no film and a neutral density
filter on the lens.  A calibrated image is then produced by dividing 
the image of interest by the calibration image (after bias and
dark current subtraction from both images).

In any case, if your illumination is constant over your measurements
and calibrations, there is no need for it to be perfectly uniform.
The illumination nonuniformities will be removed along with the CCD
nonuniformities.
 
--
+--------------------------------------------------------------------+
|Dick Wallingford      | Internet: dickw@iastate.edu                 |
|Center for NDE        | Packet  : wd0anb@n0an.ia.usa.na             |
|Iowa State University | "This river don't go to Aintree" - S.H.     | 
+--------------------------------------------------------------------+