HDTenEightyP/NetNews huggingface dataset:
From: kgrossha@radford.vak12ed.edu (Kurt Grosshans)
Subject: Re: Where should beginner begin?
Organization: Virginia's Public Education Network (Radford)
Date: Sun, 22 Nov 92 02:34:47 GMT

Above all, don't get discouraged. If you come to a passage in
the text that you do not understand, skip it and go on. Keep in
mind, if you understand only 10% of what you read, it's 10%
more than what you started out with.
-- 
Kurt Grosshans
kgrossha@radford.vak12ed.edu
From: paul@mtnmath.UUCP (Paul Budnik)
Newsgroups: sci.physics
Subject: Re: Lowneheim-Skolem theorem (was: Continuos vs. discrete models)
Date: 22 Nov 92 16:20:38 GMT
Organization: Mountain Math Software, P. O. Box 2124, Saratoga. CA 95070

In article <1992Nov22.002703.5865@CSD-NewsHost.Stanford.EDU>, pratt@Sunburn.Stanford.EDU (Vaughan R. Pratt) writes:
> In article <368@mtnmath.UUCP> paul@mtnmath.UUCP (Paul Budnik) writes:
> ...
> >The discussion on L-S has apparently misled you. I believe that the
> >space-time manifold is discrete, i. e. not continuous. There are many
> >ways to discriminate between a continuous and discrete model and this
> >has nothing to do with countability.
> 
> So why this raging debate about how many reals, then?

I have tried to move it with limited success to `sci.logic' where it belongs.
However there is one aspect of the debate that I think is relevant to
physics. It is my excuse for starting the debate here. There is a
tendency today to see the continuum as a natural God given entity similar
to how people once regarded Euclidian geometry. The Lowenheim and Skolem
theorem shows that there is a certain arbitrariness to this concept.

Paul Budnik
From: antennae@gn.apc.org
Newsgroups: sci.physics
Subject: Ghostbusters
Date: 21 Nov 92 23:08:00 GMT
Nf-ID: #N:gn:1541700010:000:854
Nf-From: gn.UUCP!antennae    Nov 21 23:08:00 1992



My 7 year old son won't go upstairs on his own because he is afraid
of ghosts.  I told him I'd give him a 'charm' to scare them off and
found a tiny, beautifully carved and painted, soapstone tiger which
seems to have done the trick.

Can you physicists do as well? 

1)  For the purposes of the exercise, assume that ghosts exist and
manifest themselves in the ways so often described - shimmering figures
that vanish through solid materials and into thin air - apparitions
dressed in long-outmoded fashions - sensations of coldness -  noises -
objects moved apparently by themselves.

2)  Can anyone suggest an explanation for any/all of these phenomena
that arises out of physics rather than metaphysics?

The purpose of this?  Not to prove that ghosts exist - I don't care
whether they do or not - but to see how inventive physicists can be.

Indra
Newsgroups: sci.physics
From: snyder@henry.ece.cmu.edu (John Snyder)
Subject: Re: UFO EVIDENCE VS. Carl Sagan
Organization: Physics Department, Carnegie Mellon University
Date: Wed, 18 Nov 1992 18:54:22 GMT

In article <kkretsch.721999974@unix1.tcd.ie> kkretsch@unix1.tcd.ie (kevin patrick kretsch) writes:
>In <16NOV199212515920@utkvx2.utk.edu> djpegg@utkvx2.utk.edu (PEGG, DAVID J) writes:
>
>>In article <kkretsch.721932625@unix1.tcd.ie>, kkretsch@unix1.tcd.ie (kevin patrick kretsch) writes...
>>>         Apparrently, the most closely guarded secret
>>>in the U.S. government regards how the UFOs were 
>>>powered. This, I believe, involves harnessing the
>>>potential energy of the earth's magnetic field.
>
>>The obvious question is:
>>	If they're powered by the earth's magnetic field, how
>>did they get to earth in the first place
>
>All right David, perhaps I should have generalised the statement.
>Let's say the following:
>              .....Powered by harnessing the potential energy of
>the magnetic field of an arbitrary planet.

However the question remains:  What do they do between planets, out in space,
travelling the mostly empty space between solar systems?  The (mainly dipole)
magnetic field of a planet dies-off rather quickly with distance (something
like 1/r**3).  So, how are they powered out there?

Or do they use an entirely different type of starship, and the UFO's that
we see are merely "shuttlecraft"?

Enquiring minds want to know...

John
snyder@henry.ece.cmu.edu


Newsgroups: sci.physics
From: palmer@sfu.ca (Leigh Palmer)
Subject: Re: Why "p" for momentum?
Organization: Simon Fraser University
Date: Mon, 16 Nov 1992 19:40:45 GMT

In article <1992Nov14.133853.10928@vpnet.chi.il.us> mox@vpnet.chi.il.us
(William Moxley) writes:
>Does anyone know why "p" was chosen to represent momentum?  Other than
>that "m" was already taken?

According to my old machanics text (Synge & Griffith) "P" stands for force (or,
perhaps, phorce). Newton's second law was written as

                         P = kmf

with appropriate boldface for vectors. f, of course, represents the
Gaelic for acceleration, which is "fastering".

Leigh
From: emarkp@soda.berkeley.edu (E. Mark Ping)
Newsgroups: sci.physics
Subject: Re: TIME HAS INERTIA. ABIAN replies to PING
Keywords: Principles (A1)  and (A2).  Repelling Forces explained
Date: 18 Nov 92 22:58:42 GMT
Organization: U.C. Berkeley, CS Undergraduate Association
NNTP-Posting-Host: soda.berkeley.edu

In article <abian.722057158@pv343f.vincent.iastate.edu> abian@iastate.edu (Alexander Abian) writes:
}>  Hmm.  This sounds extremely circular to me.  I barely even had to type the
}>second sentence (just cut and paste).  Sounds like you're not answering
}>anything.
}
}     Several times you have mentioned to me  " Abian, you're not answering
}anything".
}
}     Well, I am answering this:  I am not forcing you to read TIME HAS
}
}INERTIA.  Put this subject on your Kill File, like many have already done.
} 
}     Sincerely,
}                                              Alexander Abian

  I refuse to be forced off a thread by someone who utterly refuses to
substantiate a theory which he claims to be deserving of a Nobel Prize.

  The largest part of this thread is taken up by people saying "How does
your theory explain this?" -- then your answer, then many posts criticizing
your answer, etc.  However, you never back up your answers with more than A1.
But you cannot prove A1 by quoting it.  And if you deserve a Nobel Prize,
you should be able to satisfactorily prove it.

  I would like to address another short issue.  I find it offensive that you
claim to know the feelings of other people and their motivations for
posting.  Calling someone jealous for not coming up with your idea first
smacks of narcissism.  Perhaps they actually don't believe that your theory
is correct.  Or perhaps they (like me for instance) don't believe that this
belongs in physics, but in metaphysics at best.  You see, you are trying to
explain the great why, whereas physics tries do describe the great how.

------------
E. Mark Ping
emarkp@soda.Berkeley.EDU

  "Stand aside, I take large steps."  --Michael Dorn
  "Say, that's a nice bike."          --Cyberdyne Systems T-1000
  "Pituita es."                       --Unknown Latin Scholar
From: corleyj@helium.gas.uug.arizona.edu (Jason D Corley )
Newsgroups: sci.physics
Subject: Re: TIME HAS INERTIA    ABIAN replies to  INDRA
Keywords: Principles (A1)  and (A2).  Reply to INDRA  11-14-92
Date: 17 Nov 92 02:30:54 GMT
Organization: University of Arizona, Tucson, AZ

In article <1992Nov16.230803.10096@galois.mit.edu> jbaez@riesz.mit.edu (John C. Baez) writes:
>In article <1992Nov15.203056.14720@organpipe.uug.arizona.edu> corleyj@helium.gas.uug.arizona.edu (Jason D Corley ) writes:
>
>>Indra, the real answer is that this is caused by the electromagnetic
>
>You are clearly referring to Kaluza and Klein (two folks whose names
>begin with K!) but they proved no such thing, so this is thoroughly
>misleading.  They indeed came up with a theory that explained
>electromagnetism in terms of gravity in 5 dimensions, but this theory
>has never been widely accepted, much less "proved".

I stand corrected.  When I wrote "proved" I meant it in the
mathematical sense, not the experimental.  (To tell the truth,
I can't envision an experiment that would be _able_ to prove
that these extrapolations are true).  Given, though, what we
know about gravity and how it works, the work is correct.
As for its acceptance, the part I believe not to have been
accepted is the result that the universe exists in 5 dimensions
(see above comments on experimentalism).  The actual mathematics
is unassailable (at least _I_ can't assail it ;-), but the
results it leads to may seem unacceptable.  However, with the
extra dimensions being proposed in superstring theory gaining
more and more acceptance, perhaps a review of Kaluza and Klein
and their ideas might be in the works!

	Jason
From: columbus@strident.think.com (Michael Weiss)
Newsgroups: sci.physics
Subject: Physics and metaphysics (was: Lowneheim-Skolem theorem)
Date: 19 Nov 92 10:51:53
Organization: Thinking Machines Corporation, Cambridge MA, USA
	<TORKEL.92Nov18114047@isis.sics.se> <361@mtnmath.UUCP>
	<TORKEL.92Nov18193457@bast.sics.se>
NNTP-Posting-Host: strident.think.com
In-reply-to: torkel@sics.se's message of Wed, 18 Nov 1992 18:34:57 GMT

First, I'd like to correct a typo in the subject line that has perpetuated
itself: Lowneheim-Skolem should be Loewenheim-Skolem.


Next: Paul Budnik says:

     >This would be a valid argument if uncountable had an absolute definition.
     >I think uncountable is only meaningful relative to some formal system.

Torkel Franzen replies:

     Yes. However, this is a peculiar philosophical dogma which on the face of
   it has nothing to recommend it, and in particular, has nothing to do with
   ordinary mathematics.

This is a philosophical argument that can go on for as long as
USENET stays up.  But I don't see that it has anything to do with the question:
what is right mathematical framework for modelling the physical universe?

Assuming one could axiomatize, say, QED as a consistent first-order theory
(insert obligatory comment by John Baez on how this hasn't been done yet--
that is, the combination of defining the formal system QED and proving
Con(ZF)-->Con(QED) hasn't been carried out), it follows that there is a
countable model that looks EXACTLY LIKE the continous model, so far as
statements we can make in the language of the theory.  And if the
axiomatization is worthy of the name, then such statements are all a
physicist cares about.  Metamathematics is metaphysics, in this case.

Paul has suggested that physics should be reformulated using finite
difference equations instead of partial differential equations.  Clearly we
are talking about a change that is visible WITHIN THE FORMAL SYSTEM, so the
Loewenheim-Skolem theorem-- and any philosophical opinions about what it
really means-- are all irrelevant.

More trivial, but still worth noting: someone who believes whole-heartedly
in the Platonic reality of the whole ZFC mathematical universe, could still
maintain that spacetime is, on a small enough scale, discrete.
From: ric@hpspdla.spd.HP.COM (Ric Peregrino)
Date: Thu, 19 Nov 1992 19:35:27 GMT
Subject: Re: Covariant vs. Lie Derivative in Gen. Rel.?
Organization: HP Stanford Park - Palo Alto, CA
Newsgroups: sci.physics


>Well, what you are calling "any non-null vector" is precisely what I
>would call "any non-null tangent vector."  To be precise, the formula
>
> j
>v A   (x)
>   i;j
>
>makes sense whenever v^j is a list of numbers, but this formula
>expresses in a certain coordinate system the covariant derivative of A
>in the direction given by the tangent vector v, which has components v^j
>in that coordinate system.

Well, what if I want to know the "covariant derivative of A in the
direction of w, and w=2v? Then this covariant derivative in the
"same direction" would not be the same. This use of "direction" is not
what I am familiar with.

>The best one can say in old-fashioned lingo is that the connection IS
>the Christoffel symbol Gamma (which Ric confusingly calls G

I used G for Gamma, which is not necessarily the Christoffel symbol of the
second kind. I understand from Warren that this G is the connection. A
particular connection would be G = {ij,k}. But there are an infinite set
of connections which produce a new covariant index on a tensor through
covariant differentiation.

> The answer is just that *every* vector on the
>manifold is in the tangent space (ie. every vector is tangent to some curve).

Then why bother calling it a tangent vector, when calling it a vector would
suffice? You save typing one word and confusing me with a non-necessary term.
Or is there some case where a mere vector would not suffice? (see above w=2v)

>Ric Peregrino's problems with what I'm saying may simply be due
>to not knowing some definitions, namely of "connection" and "tangent
>vector".

Agreed. Does a tangent vector always have norm = 1? If not, what about the
definition of direction?

Thanks for the reference. Hope I'm not too stupid.

--------------------------------------------------------------------
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: jfb@draco.macsch.com (John Baskette)
Subject: Re: Religion & Physics Don't Mix
Organization: MacNeal-Schwendler Corp.
Date: Fri, 20 Nov 92 19:46:31 GMT

Subject: Re: Religion & Physics Don't Mix

In article <1ei90dINNhgs@chnews.intel.com> bhoughto@sedona.intel.com (Blair P. Houghton) writes:
>In article <1ei39gINNf3o@chnews.intel.com> bhoughto@sedona.intel.com (Blair P. Houghton) writes:
>>won't last a tenth of the 7000 years the Great Pyramid's
>>owned the planet.
>
>Uh-oh.  7000?  I want to say 4500, but that's the
>Iceman's date.
>
>Nuts.  Anyone remember when the GP was completed?

The Great Pyramid was completed about 2650 B.C. by the Phaoroah
Cheops (aka Khufu) in the 4th dynasty of the Old Kingdom.

Your 4500 number is pretty much on the money.

John

Newsgroups: sci.physics
From: mccall@mksol.dseg.ti.com (fred j mccall 575-3539)
Subject: Re: History of AC vs DC Power
Keywords: alternating current, direct current
Organization: Texas Instruments Inc
Date: Wed, 18 Nov 1992 20:44:05 GMT

In <1992Nov11.154425.8399@speedy.aero.org> steve@pepe.aero.org (Steve Sedlacek) writes:

>A question came up at lunch yesterday:  Why is our power system completely
>AC?  What are the historical and physical factors which led to the present
>power grid?  I beleive there are some DC high power transmission lines in
>Europe.  A related question concerns the supposed effect of EMF on cancers,
>especially in children.  A new Swedish study apparently confirms a moderate
>correlation between living near high-power transmission lines and cancers.
>Possibly the static field of DC transmission would be "less damaging" than
>the fluctuating field from AC?  Again, what is the HISTORY and WHY should
>power transmission be AC (I assume it is more than just transformers to
>step voltage up and down being easy for AC).

Well, actually it isn't.  Isn't there some stupid rule that puts large
taxes on AC power transmission across state lines?  I seem to remember
that there is, and that what the power companies do is convert the
power to DC on the transmission side of the line, send it across (tax
free), and then change it back to AC on the other side for further
transmission (a process referred to as 'wheeling', if I'm remembering
correctly).  Even with the power losses involved in the two changes
and the expense of the 'wheeling' stations, it works out to still be
cheaper than paying the tax.

-- 
"Insisting on perfect safety is for people who don't have the balls to live
 in the real world."   -- Mary Shafer, NASA Ames Dryden
------------------------------------------------------------------------------
Fred.McCall@dseg.ti.com - I don't speak for others and they don't speak for me.
Newsgroups: sci.physics
From: abond@rvgs.vak12ed.edu (Andrew H. Bond)
Subject: Re: A "Paradox"
Organization: Virginia's Public Education Network (Roanoke)
Date: Tue, 17 Nov 92 08:46:49 GMT

Benjamin.J.Tilly@dartmouth.edu  writes:
> Here is an interesting problem which I thought of. It is well known
> that a charged particle moving through a magnetic field does not gain
> or lose kinetic energy. However it is also well-known that a magnet
> moving through a magnetic field can gain kinetic energy. But a magnet
> is a collection of charged particles each of which does not gain
> kinetic energy so how can this be? I believe that I know the answer but
> I will just leave this to see if other people come to the same
> conclusion that I have.
> 
> Ben Tilly

The symmetry in electromagnetics suggests that electric field and electric
charge have counterparts in magnetic field and "magnetic
charge". The only problem with this idea is that there seems to
be no magnetic charges. That is there are no isolated point
objects from which magnetic field lines emerge. A magnetic
field comes from MOVING electric charges! I think that this is
sufficient to explain your "paradox" 

ref. Halliday & Resnick _Fundamentals_of_Physics_3rd_ed._ 
	Wiley 1988 (See ch. 30)
-- 
Andrew H. Bond, Roanoke Valley Graduate Center
From: jmorris@spider.co.uk (John Morris)
Newsgroups: sci.physics
Subject: Re: How can you measure the following ?
Keywords: stopwatch
Date: 20 Nov 92 14:13:03 GMT
Organization: Spider Systems Limited, Edinburgh, UK.

In article <1992Nov19.115552.16917@daimi.aau.dk> snil@daimi.aau.dk (Sven Nielsen) writes:
>In how many ways can you measure the height of a tall building using only
>these three tools : Stopwatch, barometer and tape measure.
>Now use your imagination. I'll give a few examples :
>
>1. Throw the barometer out from the top of the building and use the stopwatch
>to measure the time it takes before the barometer hits the ground. The height
>h = g/2 * t^2 ............
>
>2. Make a pendulum of the barometer and the tape measure. Lower the barometer
>until it almost touches the ground then let it swing and measure the period 
>using the stopwatch.  h = g * T^2 /(4*pi)^2   (I think ...)
>
>3. While doing 2. just read out the value on the tape measure.
>
4. Go to the architect who designed it and say "If you tell me how tall
that building is I will give you this fine barometer..."

:-)

John.


-- 
-John Morris-Spider Systems Ltd-031 554 9424-jmorris@spider.co.uk-GM4ANB@GB7EDN-
From: phys58@jetson.uh.edu (Hortvet, Douglas Richard)
Newsgroups: sci.physics
Subject: Lightning and Ball Lightning
Date: 20 Nov 1992 16:48 CST
Organization: University of Houston
Distribution: usa,world
NNTP-Posting-Host: jane.uh.edu
Keywords: Lightning, Ball Lightning
News-Software: VAX/VMS VNEWS 1.41    

I am interested in references, current and past, regarding experiments and 
theory regarding lightning, specifically ball lightning. I have heard there is
some work going on in Japan with artificial ball lightning generation attempts,
but have no information.

The literature on these topics is somehwat sparse, no doubt a result of the 
rarity of the natural phenomena, and the inability or great difficulty of 
artificial generation.

Any comments/reference recommendations would be appreciated.

					Thanks,


					Doug Hortvet	 
Newsgroups: sci.physics
From: bhv@areaplg2.corp.mot.com (Bronis Vidugiris)
Subject: Re: Auto-Deletes of Postings by Name/Phrase
Organization: Motorola, CCR&D, CORP, Schaumburg, IL
Date: Fri, 20 Nov 1992 23:14:18 GMT

In article <1992Nov20.153722.5966@asl.dl.nec.com> terry@aslws01.asl.dl.nec.com (Terry Bollinger) writes:
)Hi folks,
)
)Since there are a lot of different threads and authors on this group,
)I thought I'd mention that if you use "rn", you can do very broad
)auto-deletes that will ensure that you can keep the focus on what
)*you* want to talk about.

(description of kill-files omitted)

One thing I should mention - if you are insatiably curious, and concerned
that you might 'miss something', you can replace the command 'j' to
junk an article with :=:j to display the title of the deleted article and
THEN junk it.

I.e. /^From: bhv@/h:=:j will select articles authored by me, display
the subject line of said articles, and then 'junk' them.


Newsgroups: sci.physics
From: torkel@sics.se (Torkel Franzen)
Subject: Re: Scientists debunk astrology...and what else?
Organization: Swedish Institute of Computer Science, Kista
Date: Wed, 18 Nov 1992 12:07:35 GMT

In article <1992Nov16.190651.8644@sierra.com> ande@sierra.com (Ande Rychter) 
writes:

   >Astrology is to astronomy what MacDonald's food is to gourmet dining.  

  That's a pretty odd comparison. Could you elaborate? (I take it you
are not saying that astronomy is an absurdly expensive swindle?)
From: firth@sei.cmu.edu (Robert Firth)
Newsgroups: sci.physics
Subject: Re: Continuos vs. discrete models Was: The size of electrons, ...
Date: 16 Nov 92 13:12:02 GMT
Article-I.D.: sei.1992Nov16.131202.17710
Organization: Software Engineering Institute

In article <350@mtnmath.UUCP> paul@mtnmath.UUCP (Paul Budnik) writes:

>This well known result is called the Lowneheim and Skolem theorem. The
>idea of the proof is that a formal system is a computer program for enumerating
>theorems. The names of all real numbers created by such a program are
>obviously countable.

Well, yes, the names of any set of things created by an "enumeration"
program muct be countable, by definition.  But that's not what you
originally claimed.  You said:

>For example the real numbers definable in any consistent formal system
>are countable.

By what sleight of hand did "definable" change into "enumerable"?  Isn't
that the old constructivist premise (or fallacy, as most of us think).
Newsgroups: sci.physics
From: dacosta@prl.philips.nl (Paulo da Costa 42147)
Subject: Re: TIME HAS INERTIA.   Att:  PRATT  FUND. THM. OF ALGEBRA 
Keywords: CORRECTION        FUNDAMENTAL THM. OF ALGEBRA
Organization: none
Date: Wed, 18 Nov 1992 17:56:01 GMT

In article <abian.722071648@pv343f.vincent.iastate.edu> abian@iastate.edu (Alexander Abian) writes:
>In <abian.721303213@pv343f.vincent.iastate.edu> abian@iastate.edu (Alexander Abian) writes:
[...]
>>(3)   1/(kz^n + ...+ bz + a)  =  (1/k) z^(-n) + ........
>> 
>>But (3) shows that  0  is an essential isolated singularity of 
>>                   
>>                    1/(kz^n + ...+ bz + a)
>> 
>>contradicting (2).  Hence our assumption is false and the Theorem is
>>proved.

This step fails miserably. Reality check: You must have a<>0 (otherwise
your polynomial would have a root at z=0, contrary to your assumption).
In this case, the inverse of the polynomial at z=0 is just 1/a.  Your
talk of "essential isolated singularity" is total crap, the function is
even CONTINUOUS there (i.e., your expansion under (3) is plain wrong --
"long division" is not what you did there).

>> PS.  I know all the standard proofs e.g., by Liouville's Thm.
>       But no proof is as gorgeous as the above. [...]

That's because those are right, the above is wrong.

What a crackpot.
-- 
-- Paulo da Costa           /\/\   Minha terra tem palmeiras   /\/\
-- dacosta@prl.philips.nl   \/\/   Onde canta o sabia'...      \/\/