HDTenEightyP/NetNews huggingface dataset:
From: huber@cs.arizona.edu (Eric N. Huber)
Newsgroups: sci.physics
Subject: Re: Heard of VIRTUAL PARTICLES???
Date: 10 Apr 92 21:10:38 GMT
Organization: U of Arizona CS Dept, Tucson

From article <1992Apr9.233448.1@acad2.alaska.edu>, by assib@acad2.alaska.edu:
> The other day a friend of mine mentioned 'Virtual Particles...'
> Could I get some more info on this?
> 
> If you have any feedback, send to:
> ----------------------------------
>       ASSIB@ACAD2.ALASKA.EDU
Put simply, the are an artifact of the uncertainty principle.  One uncertainty
pair (for the sophisticated, read 'set of non commmuting operators') is 
energy and time.  The more certain you are about the energy of a system, the 
less certain you are about the time interval during which the system has the
given energy.  Conversly, if you measure the system over a certain time 
interval, the energy is slightly uncertain. 
	Here's the trick.  This 'extra' energy from the uncertainty in the 
energy measurement can take the form of a particle.  A new particle essentially
steals that energy from the uncertainty and uses it to create its self(e=mc^2).
The particle is free to exist during the uncertainty in the time interval.
	So what happens is the little bit of energy that may or may not be 
there is used to create a particle that only exists for the time that may
or may not be present; it sneaks out when no one is looking, these are 
virtual particles.
	Now the question comes of do these virtual particles really exist, or
like i, are they just a figment of our imagination?  The usual experiment I've
heard of involves a free electrical charge in space.  If virtual particles 
exist, they should be popping into existance around the electron in the form
of virtual positrons.  These virtual positive charges will 'shield' the
electron's charge, and the drop may be measured.  Neat trick!
	Hope that was easy enough to follow.

-- huber@cs.arizona.edu
From: DOCTORJ@SLACVM.SLAC.STANFORD.EDU (Jon J Thaler)
Newsgroups: sci.physics
Subject: Re: Right handed neutrino
Date: 7 Apr 92 21:41:32 GMT
Organization: Stanford Linear Accelerator Center

Erratum to my last post...

I've obviously been spending too much time with electronics lately.
The neutrino mass generation mechanism is "see-saw," not "push-pull."
Newsgroups: sci.physics
From: platt@watson.ibm.com (Daniel E. Platt)
Subject: Re: simple question
Date: Wed, 08 Apr 1992 17:34:59 GMT
Disclaimer: This posting represents the poster's views, not necessarily those of IBM
Organization: IBM T.J. Watson Research Center

In article <9204080901.aa00587@Paris.ics.uci.edu>, kibler@turing.ICS.UCI.EDU (Dennis Kibler) writes:
|> How is radioactive dating done?
|> 
|>  I understand that by knowing the current % (say Z) of X in Y,
|> and the half-life of X, that we can project backwards
|> and figure out the % (say Z') of X in Y at any previous time.
|> So to figure out the age of Y  we need to know the original
|> percentage of X in Y.  But how is that known?
|> 
|>  Let me put it in a more concrete form. Suppose we use carbon
|> dating to measure the age of a fossilized plant. I don't
|> understand why we aren't measuring the age of the carbon,
|> created I presume at the some time before the age of the earth,
|> rather than the age of the plant.

Carbon 14 dating is relatively short lived (could stretch it
to a few hundred thousand years).

The question you raise is not trivial.  There has been a lot of
research about this question, as it has been raised in the
context of trying to figure out if some cultural traits spread
through diffusion or emerged in parallel.  One of the pioneers in
the question seems to have been Colin Renfrew (a historian, not a
physicist).  One of the techniques they used in trying to
calibrate the amount of C14 was to match dates with tree-ring
data; they took samples from around the globe, and were able to
reconstruct a fairly continuous set of tree-ring matches at
several sites.  The results seemed to show that C14 was fairly
homogenous in the time scale of fluctuations; the fluctuations
were not small (its large enough that extrapolations backwards
sometimes come up with multiple roots to the equations).  If
there is ambiguity, it must be resolved in some other way
(pottery, geology, etc).  Renfrew wrote a book on this in the
early '70's.


Dan
From: platt@watson.ibm.com (Daniel E. Platt)
Subject: Re: simple question
Date: Thu, 09 Apr 1992 14:16:49 GMT
Disclaimer: This posting represents the poster's views, not necessarily those of IBM
Organization: IBM T.J. Watson Research Center

In article <1992Apr8.193655.27457@cs.yale.edu>, rescorla@rtnmr.chem.yale.edu (Eric Rescorla) writes:
|> In article <1992Apr08.173630.1785@watson.ibm.com> platt@watson.ibm.com (Daniel E. Platt) writes:
|> >In article <1992Apr8.161532.24698@cs.yale.edu>, rescorla@rtnmr.chem.yale.edu (Eric Rescorla) writes:
|> >The concentrations have not been ~ constant over time.
|> >
|> >See some of Colin Renfrew's work...  You'd find it interesting...
|> It was my impression that they had been constant to within say 50%,
|> which was all I meant to suggest.

50%?  Wow!  That's essentially 1 half-life... or around 8,000 years...

In any case, people really needed to be able to tell whether technology
developed in parallel and independently, or whether it had occured by
diffusion.  Even a few hundred years makes a difference with respect to
that question.  Given such wide fluctuations, it is common for some
older artifacts to date younger than young artifacts on the simple
assumption of radiocarbon content...

Dan
From: sichase@csa1.lbl.gov (SCOTT I CHASE)
Newsgroups: sci.physics
Subject: Re: terminal particle energy for accelerators
Date: 17 Apr 92 19:02:36 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 <1992Apr16.155454.1@sscvx1.ssc.gov>, draper@sscvx1.ssc.gov writes...
> 
>Just to reiterate a point I made earlier, the limitation for an SSC-type
>machine is NOT the radiation, but the magnetic field used to constrain the beam
>into a circle. The magnetic field required to collapse a 20TeV ring to the size
>of a meter radius, whether it's electrons or protons or Buicks (the latter
>suffering almost no synchrotron radiation at all), would be 60,000 Tesla!
> 

Of course, if you had an accelerator that could yield 20 TeV/meter, then
there would be no need to make it a ring.  You would just make a 100 meter
long linear collider with 2000 TeV per beam.  Accelerators are only rings in
the first place because the feeble accelerating gradients must be applied over
and over again to get the high energies needed for useful physics.

-Scott

--------------------
Scott I. Chase
SICHASE@CSA2.LBL.GOV
From: sichase@csa2.lbl.gov (SCOTT I CHASE)
Newsgroups: sci.physics
Subject: Re: People against Supercollider???
Date: 7 Apr 92 20:11:07 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 <8070@sun13.scri.fsu.edu>, jac@ds8.scri.fsu.edu (Jim Carr) writes...
>In article <22528@dog.ee.lbl.gov> sichase@csa1.lbl.gov writes:
>>
>>  ... comments on value of investing in accelerator R&D deleted ...
>>
>>The reason that we don't is that the particle physicists are in a race against
>>time.  You don't do good physics by verifying someone elses result.  This
>>competative incentive to move fast is a strong driving force in the advancement
>>of science.  For the most part it is a very good thing.  However, in this case
>>I wonder if we are leaping just a little to soon, without looking quite enough.
> 
>Sometimes (?) you do not do good physics when you are in a hurry.  Shall we 
>forget the Oops-Leon particle (Lederman's miss on the Upsilon) among others? 

Lederman later got the Upsilon, did he not?  He also has been in on quite 
a few other of the most important discoveries in the last 30 years, such as
the proof of the existence of lepton families, for which he shared the Nobel
prize.  It's not quite fair to pull out one mistake from a career of excellence
matched by perhaps nobody currently living.  

>I think the competition is driving the field and not the physics.  If it 
>were the physics, the field would have said that we should turn off FNAL 
>as soon as top is found and put all of those resources into the critical 
>area, the SSC search for the Higgs.  It has not said this.  And do not 
>think I exaggerate: CERN has succeeded because it moved resources to attack 
>what it thought were the best physics problems, and it was correct. 
> 

But you have proved my point.  CERN was effective at winning the race.  They
chose well, focussed their resources, and got the big win.  It has driven the
field on to new and better things, opened up vast new research possibilities,
and been a haven for theorist and experimentalists to pursue the best
high-energy physics possible.  But it has not put ALL its eggs in one basket.
LEAR is running, and doing great hadron physics.  The SPS is still running 
protons and now runs heavy-ions for the high-energy nuclear physics community
as well.  And they have other machines on the drawing board.  They have a very
healthy program.  

>What will you do 2 years after the SSC is turned on and the Higgs found and 
>the race is over?  If the justification is the race, and not physics, it 
>will be hard to justify the field when the race is won or lost.

Surely you know that the Higgs (or whatever really breaks SU(2)xU(1))  is not
the end-all of particle physics at the SSC.  There are many other goals, and 
dozens of experiments which have been proposed to perform a broad program 
of fundamental research, including the possibility of running heavy-ions for
you and me, Jim, sometime far into the future.

-Scott

Newsgroups: sci.physics
From: tolman%asylum.utah.edu@cs.utah.edu (Kenneth Tolman)
Subject: What is not being conserved?
Date: 9 Apr 92 21:38:32 MDT
Organization: University of Utah CS Dept

   In QM there is a probability that a photon will end up "hitting" a
certain spot.  If there is only one photon, and it has a nondetermined
end point, then some quantity is not being conserved.  Consider if I threw
a ball, and then it appeared randomly.  How can there be equal and opposite
reaction unless it is going to a specific place?

   Obviously I have something wrong.  Does a photon have absolutely zero
momentum?  I thought that the idea behind solar sailing was to take 
advantage of incredibly small momentums.

  The other possibility is that it retroactively changes the transmitter.
This seems pretty dubious.
   
  Any nondeterminisitic phenomena has this property.  In radioactive decay,
the unknown is time.  There never has been postulated a conservation of time,
so this violates no laws.  Also, the amount of time an electron is coupled
is a function of time, but again time is a friendly thing.

Comments?
From: DOCTORJ@SLACVM.SLAC.STANFORD.EDU (Jon J Thaler)
Newsgroups: sci.physics
Subject: Re: Interesting time travel paper
Date: 16 Apr 92 22:05:05 GMT
Distribution: sci.physics
Organization: Stanford Linear Accelerator Center

srctran@world.std.com (Gregory Aharonian) says:

> March 28, 1992 issue of New Scientist, page 23, has an interesting
> article reviewing an article in Physical Review D (October 1991) in which
> David Deutsch of Oxford uses the many-worlds hypothesis to show how one can
> how time travel without the paradoxes of killing your grandfather.  He
> argues that if you could travel back in time, you would end in a parallel
> universe, whose future you could affect, without affecting your own future.
> Interesting articles.

You might look at this article, by Igor Novikov (now at the Copenhagen
University Observatory):

THE JINN OF THE TIME MACHINE: NONTRIVIAL SELFCONSISTENT SOLUTIONS.
By A. Lossev, I.D. Novikov (Nordita & Moscow, ITEP & Lebedev Inst.), 1991.
NORDITA Copenhagen - NORDITA-91-41 (91,rec.Oct.) 20 p. (submitted to
Class. Quantum Grav.).

I haven't read it, but I heard him give a talk with that title.  He argues
that the lack of 'grandfather paradoxes' might just be a boundary condition
that is automatically satisfied.  I don't recall that he discussed any
specific mechanisms which might enforce this.
Xref: sparky sci.physics:6577 sci.math:5667
From: smith@gramian.harvard.edu (Steven Smith)
Newsgroups: sci.physics,sci.math
Subject: Re: What does HORIZONTAL mean to physicists?
Date: 6 Apr 92 18:18:21 GMT
Article-I.D.: gramian.SMITH.92Apr6131821
Distribution: sci.physics,sci.math
Organization: Harvard Robotics Lab, Harvard University
Cc: karim@oak.uncwil.edu

In article <1992Mar31.181342.19797@ecsvax.uncecs.edu> karim@oak.uncwil.edu (Omar A. Karim -- UNCW Physics -- 919-395-3467) writes:

> Quick, what does HORIZONTAL mean?

Why, given a smooth manifold M and letting B denote its frame bundle
and V_b the vertical space at b in B, it is a smooth choice of a
subspace H_b in the tangent space B_b for all b in B such that
B_b = H_b + V_b (direct sum) and {H_b}_b is right invariant with
respect to the action of GL(n) on B.

Steven Smith
From: eer36024@uxa.cso.uiuc.edu (Erik Reuter)
Subject: Re: Help--quotations of physicists
Organization: University of Illinois at Urbana
Date: Tue, 14 Apr 1992 13:26:50 GMT

Here are some of my favorites. I don't have any references to when or where
these were spoken/written. In fact, it may be that some of them are
inaccurate. But they are fun.

****

I do not like it, and I am sorry I ever had anything to do with it.
      -- E. Schrodinger [on quantum mechanics]
 
Those who are not shocked when they first come across quantum mechanics
cannot possibly have understood it.
	-- Niels Bohr
 
  Surely, Professor Bohr, you do not really believe that a horseshoe over
the entrance to a home brings good luck?
  No, I certainly do not believe in this superstition. But you know, they
say it brings luck even if you don't believe in it.
      -- A house visitor and Niels Bohr
 
The eternal mystery of the world is its comprehensibility.
	-- Albert Einstein
 
But in physics I soon learned to scent out the paths that led to the
depths, and to disregard everything else, all the many things that
clutter up the mind, and divert it from the essential. The hitch in this
was, of course, the fact that one had to cram all this stuff into one's
mind for the examination, whether one liked it or not.
	-- Albert Einstein
 
Do not worry about your difficulties in mathematics; I can assure you
that mine are still greater.
      -- Albert Einstein
 
Oh, that Einstein, always skipping lectures....I certainly never would
have thought he could do it.
	-- Herman Minkowski
 
For a successful technology, reality must take precedence over public relations,
for Nature cannot be fooled. 
     -- Richard P. Feynman
 
The fundamental principle of science, the definition almost, is this: the
sole test of the validity of any idea is experiment.
       -- Richard P. Feynman
 
Physics is very muddled again at the moment; it is much too hard for me
anyway, and I wish I were a movie comedian or something like that and
had never heard anything about physics!
	-- Wolfgang Pauli
 
By nature I am peacefully inclined and reject all doubtful adventures.
But a theoretical interpretation had to be found at all costs, no matter
how high . . . I was ready to sacrifice every one of my previous 
convictions about physical laws.
      -- Max Planck

****
Erik Reuter, e-reuter@uiuc.edu
From: fcrary@ocf.berkeley.edu (Frank Crary)
Newsgroups: sci.physics
Subject: Re: "what's new" Apr-10-1992
Date: 16 Apr 92 16:10:19 GMT
Article-I.D.: agate.sk8tbINN5d7
Organization: U.C. Berkeley Open Computing Facility
NNTP-Posting-Host: sandstorm.berkeley.edu

In article <14APR199212561646@sscvx1.ssc.gov> sawyer@sscvx1.ssc.gov (Lee Sawyer) writes:
> Seriously, isn't CIS the accepted abbreviation now ? "CIS and Baltic
>States" would include everyone.

Georgia isn't a member of the CIS either... But I think Park is using the
"FSU" (Former Soviet Union) to imply that things haven't settled down yet
and the Commonwealth may not last

                                                          Frank Crary
							  UC Berkeley
From: daryl@oracorp.com (Daryl McCullough)
Newsgroups: sci.physics
Subject: Neutrino Shortage Solved?
Date: 9 Apr 92 15:28:03 GMT
Organization: ORA Corporation

I read in a recent New Scientist (a British science magazine that is
about at the Scientific American level of technical detail) that there
is a new explanation for the missing solar neutrinos. The explanation
wasn't given in any detail in the article, but the rough idea is the
following:

The usual theoretical calculations done for nuclear fusion treats the
case of collisions of bare nuclei. That is, only protons and neutrons
are considered. However, in an actual nuclear reaction in the center
of stars, there are huge numbers of electrons floating around. The
electrons have an influence on the fusion reaction, because the
negatively charged electrons to a certain extent shield the protons
from the full effect of their electrical repulsion. Thus, the
electrons can act as a kind of catalyst for fusion reactions, thus
lowering the temperature necessary to achieve a sustained reaction.

I don't know enough about fusion to understand how the temperature
enters into neutrino calculations, but in the article it was claimed
that the effect of the electrons would explain the missing neutrinos.

Is there anyone familiar with this explanation who can give a more
complete explanation (or explain why it is nonsense)?

Daryl McCullough
ORA Corp.
Ithaca, NY
From: routd@woods.ulowell.edu
Newsgroups: sci.physics
Subject: EMAIL for ICTP,TRIESTE, ITALY.
Date: 14 Apr 92 20:52:32 GMT
Organization: University of Lowell

Dear netters,
		Could anybody send me the EMAIL address and/or FAX number
of Condensed Matter Secretary, International Center  for Theoretical Physics 
(ICTP), Trieste, Italy. 

		Thanks.
From: gsteckel@vergil.East.Sun.COM (Geoff Steckel - Sun BOS Hardware CONTRACTOR)
Newsgroups: sci.physics
Subject: Re: Question about dimmer switch and lamp.
Date: 13 Apr 92 23:50:46 GMT
Reply-To: gsteckel@east.sun.com (Geoff Steckel - Sun BOS Hardware CONTRACTOR)
Distribution: na
Organization: Omnivore Technology, Newton, Mass. (617)332-9252
NNTP-Posting-Host: vergil.east.sun.com

>In article <1020006@hpdmd48.boi.hp.com> rrr@hpdmd48.boi.hp.com (Rudi Rynders) writes:
>
>    Given an incandescent lamp with a dimmer switch. The lamp is on.
>...
>    switch up, no matter how slow, the light always comes on rather
>    suddenly and much brighter than in the reverse process .
>
>>This is not a physics problem, it is an electrical engineering problem.

Yes, but it has to do with the circuit triggering the triac.
The manufacturer was cheap.  Very simplified, the triac is
triggered from a `diac', a bidirectional 5-layer breakdown diode,
a variable resistor, and a capacitor.  The R-C circuit charges from
the line, and when the voltage exceeds the breakdown voltage of the
diac, the capacitor discharges through the gate of the triac and
the triac turns on.

If the diac has not triggered recently, the capacitor holds a
residual charge from the previous half cycle, opposite in polarity
to the voltage necessary to trigger.  To overcome this charge
(which is refilled every half cycle) it is necessary to advance
the control (decrease the resistance) such that the current cycle
can charge the capacitor enough to trigger the diac->triac pair.

However, once the diac has fired, there is much less residual
charge on the capacitor, so now the capacitor can charge to the
trigger voltage much sooner in each cycle, so the lamp is now
on brightly.

The cheapest cure is to use an asymmetrical trigger diac.  This
costs a few cents more than the symmetrical ones.

See a triac manufacturer's application notes for more info.

I hope this is not too confusing.
	geoff steckel (gwes@wjh12.harvard.EDU)
			(...!husc6!wjh12!omnivore!gws)
Disclaimer: I am not affiliated with Sun Microsystems, despite the From: line.
This posting is entirely the author's responsibility.
From: jfw@ksr.com (John F. Woods)
Newsgroups: sci.physics
Subject: Re: Fusion reactor disasters --- impossible
Date: 6 Apr 92 12:47:16 EDT
Distribution: na

franl@centerline.com (Fran Litterio) writes:
>Isn't liquid lithium forseen as the medium used to absorbe the
>neutrons speeding away from the fusion reaction?

Yes.

>Over time the
>lithium becomes radioactive and needs to be replaced.  Being a liquid
>would actually make it harder to manage the storage of waste over many
>decades

*Liquid* lithium is a very hot molten metal.
*Cold* lithium is a fairly reactive *solid* metal.  Easy to store.  (Of course,
you'd probably want to react it to turn it into a non-reactive ceramic or glass
for even easier storage).

Note that lithium is used to absorb neutrons because that turns it into
helium and tritium (instant fuel).  The bulk lithium might well become
radioactive from picking up bits of induced-radioactive material from pipe
walls, etc.
Newsgroups: sci.physics
From: rcain@netcom.com (Robert Cain)
Subject: Re: Interesting time travel paper
Date: Wed, 15 Apr 92 19:59:11 GMT
Organization: Netcom - Online Communication Services  (408 241-9760 guest) 
Distribution: sci.physics

But you *could* end up in a precedent of your thread.  How does he preclude
this?
-- 
Bob Cain    rcain@netcom.com   408-358-2007

"There are some strings.  They're just not attached."
                                                    Victoria Roberts
Newsgroups: sci.physics
From: platt@watson.ibm.com (Daniel E. Platt)
Subject: Re: simple question
Date: Wed, 08 Apr 1992 17:36:30 GMT
Disclaimer: This posting represents the poster's views, not necessarily those of IBM
Organization: IBM T.J. Watson Research Center

In article <1992Apr8.161532.24698@cs.yale.edu>, rescorla@rtnmr.chem.yale.edu (Eric Rescorla) writes:
|> In article <9204080901.aa00587@Paris.ics.uci.edu> kibler@turing.ICS.UCI.EDU (Dennis Kibler) writes:
|> > Let me put it in a more concrete form. Suppose we use carbon
|> >dating to measure the age of a fossilized plant. I don't
|> >understand why we aren't measuring the age of the carbon,
|> >created I presume at the some time before the age of the earth,
|> >rather than the age of the plant.
|> The percentage of C14 in the atmosphere is ~constant over time.
|> As long as you're alive, you exchange carbon with the atmosphere
|> and maintain the atmospheric concentration of C14 in your system.
|> When you die, you stop exchanging and that's the zero-time.

The concentrations have not been ~ constant over time.

See some of Colin Renfrew's work...  You'd find it interesting...


Dan