HDTenEightyP/NetNews huggingface dataset:
From: jbaez@euclid.mit.edu (John C. Baez)
Subject: Re: Order-of-Magnitude problems
Organization: MIT Department of Mathematics, Cambridge, MA
Date: Mon, 17 Aug 92 20:29:32 GMT


In article <1992Aug17.162216.9332@amhux2.amherst.edu> jkwatson@amhux1.amherst.edu (John K. Watson '92) writes:
>Rob Salgado (sal7@ellis.uchicago.edu) wrote:
>:         In trying to improve my physical intuition, I've been doing lots
>: of Order-Of-Magnitude (Back-Of-The-Envelope) problems.  
>: ...but I'm stumped by the following:
>:  
>:         Use the uncertainty principle to compute how long an ordinary
>:         lead pencil can be balanced upside down on its point.
>:                                                 [QM: Das/Melissinos p. 53]
>: Any ideas?

Guess the length L and mass m of a pencil. Suppose the top is an angle theta
away from the vertical, and suppose it is falling over at some angular 
velocity v.    Then it will fall over and hit the table at some time
t(theta, v).  I leave it to someone else to work out an an approximation
to this function t(theta,v) that is okay for small theta and v.  The
real answer will probably involve elliptic integrals, since they show up
in the formula for the period of a pendulum, but I think one should be
able to get a good-enough answer without resorting to these.  Okay, now
minimize t(theta,v) subject to the constraint  

m theta v L^2 = hbar

This constraint comes from the uncertainty principle: one can't know the
angle theta and the angular momentum m v L to accuracy better than hbar.
Of course the angular momentum is not exactly m v L^2 but that's close
enough for this sort of thing.


Newsgroups: sci.physics,sci.astro
From: carl@aoa.aoa.utc.com (Carl Witthoft)
Subject: Re: Fossil Paradox (was: Structure of Time)
Organization: Adaptive Optics Associates
Date: Tue, 18 Aug 1992 12:02:53 GMT

In article <1992Aug17.105752.29021@cco.caltech.edu> keith@cco.caltech.edu (Keith Allan Schneider) writes:
>bedding@physics.su.OZ.AU (Tim Bedding) writes:
>
>>"The Sound of Thunder", as I recall.  Which was what he heard when he got
>>back to the present to find it changed: his travelling partner blew him
>>away with a shotgun for being a jerk.  :-)
>the bullets would be collected, etc.  There was this walkway, but
>the man stepped off it and onto a butterfly.), finding that the spelling
>of a few words on a sign were changed.
x
Both of these comments accurately reflect portions of the end of this 
story.
'Nuff said by now,
I think. 
x
x
x

-- 
Bobby Newmark, aka  Carl Witthoft @ Adaptive Optics Associates
aoa!carl@bbn.com  carl@aoa.utc.com
54 CambridgePark Drive, Cambridge,MA 02140 617-864-0201
**Just say NO to HMOs**
From: sawyer@utahep.uta.edu (Lee Sawyer)
Newsgroups: sci.physics
Subject: Re: High Energy Physics Phenomenology
Summary: CFD: PDB subgroups
Date: 19 Aug 92 14:08:00 GMT
Organization: University of Texas at Arlington High Energy Physics Group
NewsSoftware: VAX/VMS VNEWS 1.41
NntpPostingHost: utahep.uta.edu
MessageID: <19AUG199208085853@utahep.uta.edu>
X-Bytes: 1577

In article <1992Aug18.234715.7364@cco.caltech.edu>, brahm@cco.caltech.edu (David E. Brahm) writes...
>moorthy@ferrari.cs.rpi.edu (Moorthy) writes:
>> I would like to know the electronic mailing lists/archival sources for
>> $K_{L} > \pi \mu \nu \gamma.$
> 
>[funny stuff deleted] 
>ObSeriousness:  I think a good place to look for such things is the SPIRES
>database PARTICLES (or REACTIONS for A + B > ...), which reproduces the
>PDB.  I see KL > pi e nu gamma (BR=1.3%), but not KL > pi mu nu gamma.
> 
>
>Staccato signals of constant information,  |   David Brahm
>A loose affiliation of millionaires and    |  (brahm@cco.caltech.edu)
>  billionaires and Baby ...                |
>These are the days of miracle and wonder,  | Disclaimer:  It was a joke,
>And don't cry, Baby, don't cry, don't cry. |   just a harmless ARGHHH...

  Is there something sutble I'm missing about this reaction ? It seems kinamatically 
feasible, and there is (as David points out) a measured branching fraction for
the corresponding electron channel. But this one isn't listed in either the 
allowed channels, or the CP violating "search" channels. So what gives ?

  But the answer to the original question is : For online reaction data,
use SPIRES or the RALDurham database. Information on accessing these can
be found in the front of the Particle Data Group's Review of Particle Propereties
(Phys. Rev _D45_, part 2 (June 1992) if you are on this side of the planet).

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

         Dept of Physics
         Univ. of Texas
               at Arlington
Newsgroups: sci.physics
From: barry@arnold.math.ucla.edu (Barry Merriman)
Subject: Re: Graduate Programs in Physics
Organization: UCLA, Mathematics Department
Date: Wed, 19 Aug 92 02:59:23 GMT

In article <Bt7Bnw.CJ7@wpi.WPI.EDU> delphine@wpi.WPI.EDU (Delphine Clomenil)  
writes:
> I am about to start my senior year as a Physics Major at Worcester  
Polytechnic
> Institue and like many others I have been working on selecting a few graduate
> schools to apply to.

If you are good, check out the University of Chicago. A great physics
department. 

Bonus: 3 Nobel prize winners, at the moment (not so much
for research, but they give it a great ambiance)
From: bweiner@ruhets.rutgers.edu (Benjamin Weiner)
Newsgroups: sci.physics
Subject: Re: Hubble constant?
Date: 13 Aug 92 20:31:25 GMT
Organization: Rutgers Univ., New Brunswick, N.J.

willner@cfa.harvard.edu (Steve Willner) writes:
>If you are willing to accept a non-zero cosmological
>constant, though, you can have a flat universe with \Omega =
>\Omega_baryon = 0.2 and old enough to solve the horizon problem, the
>structure problem, and the "oldest stars" problem.

Is this what the "isocurvature baryon" universe is?  I like the 
baryonic possibilities because we already know that baryons exist,
and in addition I would rather that dark matter were something
astronomically interesting, like so-called Pop III star remnants
or whatever, rather than a bunch of dull photinos.

It has been pointed out, however, that having a non-zero but very
small cosmological constant is reminiscent of the flatness problem:
why should it have the value it does?  That's only a problem if you
think the flatness problem is really a problem.  [what tortured prose!]

Ben Weiner
baryonic and proud of it!
From: weemba@sagi.wistar.upenn.edu (Matthew P Wiener)
Newsgroups: sci.physics
Subject: Re: 'SSC and biochemistry?
Date: 12 Aug 92 17:21:13 GMT
Reply-To: weemba@sagi.wistar.upenn.edu (Matthew P Wiener)
Organization: The Wistar Institute of Anatomy and Biology
In-reply-to: phillies@wpi.WPI.EDU (George D. Phillies)

In article <BsvnwE.36I@wpi.WPI.EDU>, phillies@wpi (George D. Phillies) writes:
>[On a hypothetical confirmation of Z0-mediated origin of biochirality]
>The people who make the discovery will likely be able to publish it
>in Nature, and may well be able to take home a Nobel Prize.

I sincerely doubt that last.

>If you want to justify SSC, it must be done on the basis of the 
>alleged importance of HEP, not on the basis of spinoffs to other 
>fields.

No one has been justifying SSC via other field spinoffs.  Just pointing
out what may be. 
-- 
-Matthew P Wiener (weemba@sagi.wistar.upenn.edu)
From: bweiner@ruhets.rutgers.edu (Benjamin Weiner)
Newsgroups: sci.physics
Subject: Re: Blue Sky and Olbers' Paradox
Date: 18 Aug 92 23:42:17 GMT
Organization: Rutgers Univ., New Brunswick, N.J.

Andrew Mullhaupt writes:
> ...  So it's the issue of which blanks you
>feel confident about filling in, or to belabor the point - where do you
>choose to stop your explanation and start your observation.

Sure, and this originally started when you criticized the explanation
of the blue sky for stopping too early.  Your point boils down to the
statement that the "scientific method" (in theory or practice) does
not help you to choose when to stop.  In theory, sure; but in
scientific practice, you stop when it no longer seems productive or
illuminating to the question at hand.  That's quite subjective, and
you run the risk of missing something important; but it's the way that
researchers have to work, and science is what researchers do, not a
disembodied set of theories.  Having said that, I think I'll stop.
Newsgroups: sci.physics,sci.math
From: timg@jpl-devvax.jpl.nasa.gov (Tim Graham)
Subject: Re: Symmetries, groups, and categories
Organization: Jet Propulsion Laboratory (NASA)
Distribution: na
Date: Fri, 14 Aug 1992 00:47:40 GMT

In article <25475@dog.ee.lbl.gov> sichase@csa2.lbl.gov writes:
>That was awesome.  Where do you find the time to post such things?  

I have to second the "awesome" part of that John.  I'm glad you take the time
to post such interesting articles.  Running the risk of sounding too adulatory,
I'd go so far as to say that it's genuinely inspiring.  Keep it up!


-- 
Tim Graham	
timg@jpl-devvax.jpl.nasa.gov	(818) 306-6196
Jet Propulsion Laboratory / California Institute of Technology
M/S 525-C193, 4800 Oak Grove Drive,  Pasadena, CA  91109
From: matmcinn@nuscc.nus.sg (Mcinnes B T (Dr))
Newsgroups: sci.physics
Subject: Re: The dangers in microwaved food...
Date: 21 Aug 92 01:44:09 GMT
Distribution: na
Organization: National University of Singapore

Of course, I could be wrong.
From: yvent@ntua.gr (Yiannis Ventikos)
Newsgroups: sci.physics
Subject: Re: sea waves
Keywords: waves
Date: 22 Aug 92 07:04:16 GMT
Organization: National Technical University of Athens


You dont have to have shallow water for breaking to occur. A body moving
under the water (infinitelly deep water) will produce breaking waves under
certain conditions. (check my other posting on the matter)
BTW turbulence ("traditional" turbulence) has nothing to do with it


 
-------

******************************************************************************
* Yiannis Ventikos                              *        DISCLAIMER          *
* Viscous Flows Group,                          * Any and all opinions that  *
* Dept. of Naval Arch. & Marine Eng.,           * I have  expressed  so far  *
* National Technical University of Athens,      * reflect  thoughts of mine  *
* P.O. Box 64070, GR-15710, Zografos, GREECE    * and  mine alone and  have  *
* Voice: (301) 7700405                          * nothing  to do  with  the  *
* Fax:   (301) 7774478                          * policy of the  Department  *
* e-mail: yvent@areti.marinentua.ariadne-t.gr   * I currently belong to.     *
******************************************************************************
From: g88s8885@giraffe.ru.ac.za (MR TF SPEARS)
Newsgroups: sci.physics
Subject: Re: I can travel faster than light (A riddle)
Date: 14 Aug 92 10:34:37 GMT
Organization: Rhodes University, Grahamstown, South Africa

In article <1161@kepler1.rentec.com> andrew@rentec.com (Andrew Mullhaupt) writes:
...
>Ever worn a baseball cap, etc.? Had an X-ray at the dentist? Used a liquid
>crystal display? Opened a door with a photocell? Used a reticle or crosshairs
>in a telescope?

>(Putting his pseudo-philosopher hat on again...)

>Is there a difference between a shadow and a diffraction or interference
>pattern? For example is a holograph a shadow? It is pretty well known that
>there is a bright spot in the center of the shadow cast by a disk. Is this
>part of the shadow?

>Later,
>Andrew Mullhaupt

I would think so, but shadow isn't really a scientific term - I think your 
average English Professor (the sort of person who puts these words into 
dictionaries) would consider the bright spot part of (or an interruption in) 
the shadow of the disk.

To add to your list, I'd definitely consider the image of a slide projector 
or an overhead projector to be a shadow, not to mention backlit LCD displays.

Tim
Newsgroups: sci.physics
From: matmcinn@nuscc.nus.sg (Mcinnes B T (Dr))
Subject: Re: Sarfatti Bio FYI
Organization: National University of Singapore
Date: Wed, 19 Aug 1992 05:19:32 GMT

What! No cosmic potato?!
Newsgroups: sci.physics
From: jbaez@zermelo.mit.edu (John C. Baez)
Subject: Re: Hubble constant?
Organization: MIT Department of Mathematics, Cambridge, MA
Date: Fri, 14 Aug 92 21:19:09 GMT

In article <1992Aug14.123540.3168@nuscc.nus.sg> scip1061@nuscc.nus.sg (Marc Paul Jozef) writes:
>
>  Dave, in your last response you write
>
>"The perturbation is not small. In fact it changes the
> large scale geometry"
>
>So you say. But Einstein doesn't agree with that. 

I think Einstein does.

I urge you again to take a look at the section of "Gravitation" on this
point.  Dave Ring, if I recall aright, has posted the page number.
Xref: sparky sci.physics:13082 sci.astro:9072
From: chad@aquarius.as.arizona.edu (Chad Engelbracht)
Newsgroups: sci.physics,sci.astro
Subject: Re: Fossil Paradox (was: Structure of Time)
Date: 19 Aug 92 21:40:44 GMT
Organization: University of Arizona, Tucson, AZ

In article <roelle.714249583@uars_mag> roelle@uars_mag.jhuapl.edu (Curtis Roelle) writes:
>carl@aoa.aoa.utc.com (Carl Witthoft) writes:
>
>>In article <1992Aug17.105608.421@ecc.tased.edu.au> ecc_jim@ecc.tased.edu.au writes:
>>>There was a short story like this where a guy trod on a butterfly and totally
>>>changed everything. What was it called?
>
>>[about time travel and all that...]
>>I know the story but forget its name.  The premise was that time travellers
>>could shoot prehistoric animals.  The guide scoped out the area so
>>they only shot animals about to die anyway, and then pulled out the bullet 
>>and took off.  I distrusted then (1970 or so) and still distrust
>>the idea that killing a butterfly is bad but killing a Tyrannosaurus
>>3 seconds early, ripping its guts open, etc. is OK  (from a time-
>>travel causality point of view :=) )
>
>Not to mention the impact of constructing the walkway used in the first place.

The story is "A Sound of Thunder" by Ray Bradbury
Newsgroups: sci.physics
From: bhoughto@sedona.intel.com (Blair P. Houghton)
Subject: Re: Hubble constant?
Organization: Intel Corp., Chandler, Arizona
Date: Thu, 20 Aug 1992 04:55:20 GMT

In article <Aug.19.18.17.20.1992.25237@ruhets.rutgers.edu> bweiner@ruhets.rutgers.edu (Benjamin Weiner) writes:
>I went into science so I wouldn't have to wear suits, silly.

If a silk fiber is so silky, what keeps a silk thread together?

				--Blair
				  "The Golden Triangle."
From: ric@hpspdla.spd.HP.COM (Ric Peregrino)
Date: Wed, 12 Aug 1992 21:33:56 GMT
Subject: Re: Annihilation?
Organization: HP Stanford Park - Palo Alto, CA
Newsgroups: sci.physics


Scott Chase writes:

>S-states must decay into an even number of photons, P-states
>into an odd number.

Matt McIrvin writes:

>Spin-aligned positronium can decay to final states with
>*more* than two photons.  For instance, a three-photon final
>state is possible.

These two statements look inconsistent. A ground state (S)
spin aligned positronium certainly can't decay into an
even number of photons with conservation of spin given that
no spin 0 photons exist. I see no problem with three photons.
Is this the source of the longer lifetime positronium?

What are the experimentally observed outcomes of an annihilation
of a positron and an electron? I assume these experiments have
been done.

--------------------------------------------------------------------------
Ric Peregrino     c/o Hewlett Packard Co.        I represent only myself
ric@spd.hp.com    1501 Page Mill Rd. Bldg. 5M    Buy low, sell high
415-857-7526      Palo Alto, CA 94304            Does a DC photon exist?
--------------------------------------------------------------------------
Xref: sparky sci.physics:13123 sci.skeptic:14707 alt.folklore.science:3071
From: tlouie@athena.mit.edu (Tom Louie)
Newsgroups: sci.physics,sci.skeptic,alt.folklore.science
Subject: Re: The dangers in microwaved food...
Date: 20 Aug 92 14:37:12 GMT
Organization: Massachusetts Institute of Technology

In article <1992Aug20.015531.7842@nuscc.nus.sg> matmcinn@nuscc.nus.sg (Mcinnes B T (Dr)) writes:
>there are serious health risks in eating.

There are serious health risks.
Newsgroups: sci.physics
From: bucknerb@bnr.ca (Brent Buckner)
Subject: Re: cos(reflection phase beam splitter) = 0 ? NO FTL?
Organization: Bell-Northern Research, Ontario, Canada
Date: Fri, 14 Aug 1992 17:33:54 GMT

In article <BsyoHE.37H@well.sf.ca.us> sarfatti@well.sf.ca.us (Jack Sarfatti) writes:
       [deleted]
>
>At last a refutation that makes sense. If
>true it would definitely mean that my device would not work.
       [deleted]
>Then, if
>it is true, we must see what happens if there is absorption.

How about recombining using a prism rather than a beam-splitter?

Wouldn't the same basic descriptions hold, with the exception
of b representing the difference in the phase shifts of the beams
encountering the prism (instead of the phase shift of the
beam reflected by the beam-splitter)?  With b=0, since the
beams incident upon the prism would undergo the same phase shift,
the analysis continues as before.

-- 
at Bell-Northern Research
voice:        (613) 765-2739
Canada Post:  P.O. Box 3511, Station C, Ottawa, Canada, K1Y 4H7
I do not claim that BNR holds these views.
From: tjn32113@uxa.cso.uiuc.edu (Thomas J. Nugent)
Newsgroups: sci.physics
Subject: Re: "What's New" July-24-1992
Date: 13 Aug 92 19:33:03 GMT
Organization: University of Illinois at Urbana

jac@ds8.scri.fsu.edu (Jim Carr) writes:

>All of which seems to ignore the one design that we actually launched! 
>Skylab was designed, two of them built, one launched and used for 
>quite some time.  It is presumably man-rated and that design could be 
>built again.  Of course one might wish to update it, but Mir has shown 
>that a simple and conservative design is the best way to get up there 
>early and stay there for an extended period of time.  

Perhaps.  But I would also consider what you are able to do up there besides
sit (float?) on your hands.  Simply put, Freedom can do alot more than Mir.
There was an excellent post recently, perhaps in sci.space, regarding the
differences between Freedom and Mir.  Freedom has more power, more space, etc.
etc. etc.  

>Except for unfortunate delays in the shuttle program, the one that we 
>launched could have been kept up there and still be used as the base 
>platform for a larger system. 

>The one thing I really do not understand in all of the discussion of the 
>need for long-term study of human biology in orbit and the recent story 
>about problems in zero-g adaptation is why none of this was studied back 
>in the days of Skylab.  

They were busy studying other things?  I imagine that there was some study
of the effects of zero-g on the astronauts.  But two(?) missions, each less
than 84 days, is definitely not enough to complete the book (probably not
even the first chapter) on the effects of zero-g on humans.

"Far better it is to dare mighty things, to win glorious triumphs, even
though checkered with failures, than to rank with those poor spirits who
neither enjoy nor suffer much, because they live in the gray twilight that
knows not victory nor defeat."
		- Theodore Roosevelt 
-- 
"To be average scares the hell out of me." -- Anonymous
Tom Nugent		e-mail: tjn32113@uxa.cso.uiuc.edu
Newsgroups: sci.physics
From: scip1061@nuscc.nus.sg (Marc Paul Jozef)
Subject: Re: Hubble constant?
Organization: National University of Singapore
Date: Mon, 17 Aug 1992 05:48:04 GMT

Dave, although you did not want to say it directly,
you have chosen to reject the idea that the global
metric of spacetime can be approximated by a
Friedmann metric. So when using G(g) = T in cosmology
-whatever the udealization for T- you tell us we are
no longer allowed to assume g Friedmann.
(You haggle about _exactly_ Friedmann. That is irrelevant;
if g is approximatley Friedmann, then G(g) is approximately
G(friedmann). If not, then explain why GR uses so
confidently G(Friedmann) = T(perfect fluid).)

Now that you have rejected this fundamental assumption
of GR cosmology, could you tell me how GR copes with
this loss? It just so happens that nearly all numerical
assertions about global scale are expressed in terms of
Friedmann metrics. Especially the `deceleration parameter q_0'
whose value is the central issue of our argument (I say
it is zero, you say it is not) is defined in terms of
Friedmann metrics.

In answer to your last question, few matter distributions
produce a pumpkin cosmology, especially if the pumpkin
is parabolic and fanning out like a flower. I would
say the only matter distribution resembling a pumpkin
is a pumpkin itself.
Through our correspondence I have learned how to prove
such assertions: because I'm right!

Lest the reader thinks that MTW has dealt with this
subject seriously, consider page 739 for a good laugh.

Newsgroups: sci.physics
From: matmcinn@nuscc.nus.sg (Mcinnes B T (Dr))
Subject: Re: That "Vision Thing"!/Teleology in Modern Physics
Organization: National University of Singapore
Date: Fri, 14 Aug 1992 04:32:54 GMT

I vote for "acid trip".
From: sichase@csa3.lbl.gov (SCOTT I CHASE)
Newsgroups: sci.physics
Subject: Re: Physics News Update #92 (8/19)
Date: 20 Aug 92 19:36:11 GMT
Organization: Lawrence Berkeley Laboratory - Berkeley, CA, USA
Distribution: usa
Reply-To: sichase@csa3.lbl.gov
NNTP-Posting-Host: 128.3.254.198
Summary: Second posting of PNUP to sci.physics
Keywords: physics news interesting cherry
News-Software: VAX/VMS VNEWS 1.3-4   

>THE ELECTRICAL CHARGE OF ANTIPROTONS AND POSITRONS has been studied
>using data from cyclotron- frequency experiments (which monitor the
>behavior of particles in a magnetic field) comparing protons with
>antiprotons and electrons with positrons, as well as spectroscopic
>measurements of short- lived states containing antimatter, such as
>positronium and antiprotonic atoms.  Richard Hughes of Los Alamos and
>B.I.  Deutch of the University of Aarhus in Denmark have calculated
>that the charges of the positron and electron are equal to about one
>part in 10**8, while the charge of the antiproton equals that of the
>electron to about one part in 10**5 (Phys. Rev. Lett., 27 July).  The
>precision of these calculations would improve if researchers could
>study antihydrogen, an atom consisting entirely of antimatter.
>(Science News, 15 August 1992.)

Of course, the author *meant* to say that they showed that the charges
were equal to *better* than a part in 10**8, etc.  No differences were found.
I might add that it is known that the charge of the electron and proton
are known to be identical to better than a part in 10^27 (though 10^24 might be 
the highest published value.)  That's how I got started in experimental
physics - as an undergrad at MIT I worked for about a year with John 
King, who did this original work, on an improvement of a few more orders
of magnitude.  The experiment went on after I left, and I don't even
know whether results were ever published, but it convinced me that 
physics is the thing to do (as if I had any doubts before that.)

-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: xie@phoenix.Princeton.EDU (Yan-bo Xie)
Subject: Re: How to make big bucks using supersymmetry
Originator: news@nimaster
Organization: Princeton University
Date: Sat, 15 Aug 1992 15:45:27 GMT

From article <1992Aug15.013809.13677@nuscc.nus.sg>, by matmcinn@nuscc.nus.sg (Mcinnes B T (Dr)):
> There is one item that you gentlemen have forgotten. Do you really think
> that american pennies will still be legal tender in 2010? By then, the
> smallest coin will be small disc of brass with $1000 inscribed on one
> side, and a portrait of R Reagan on the other.

Also SUSY may only become evident at 10**12Gev.  I would expect
a huge machine called SSSSSSC will be built (cost $60.00)
in antarctic around 2310.