HDTenEightyP/NetNews huggingface dataset:
From: moravec@Think.COM (Hans Moravec)
Newsgroups: sci.physics
Subject: Re: Blue hawks (was Blue Sky)
Date: 29 Jul 1992 19:54:51 GMT
Organization: Thinking Machines Corporation, Cambridge MA, USA
Distribution: world
NNTP-Posting-Host: turing.think.com

In article <1992Jul29.180428.29756@murdoch.acc.Virginia.EDU>, crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass) writes:
|> In article <1128@kepler1.rentec.com> andrew@rentec.com (Andrew Mullhaupt) writes:
|> >In article <1852@snap> paj@uk.co.gec-mrc (Paul Johnson) writes:
|> >
|> >>Active illumination is not an option available to eagles.
|> 
|>      In fact, it is my guess that the most inexpensive set would cost many
|>      tens of thousands of eagle-years labor, imposing large weight and
|>      aerodynamic penalties, and a whole bunch of standing around waiting
|>      for radar to be invented...

I remember a PBS (NOVA, I think) program on wartime camouflage, where a
British WWII daylight bombing raid was hidden (from fighters and
ground fire) by very bright lights mounted on the bombers.  It wasn't
necessary to cover the whole aircraft surface: just to generate enough
light to make the total brightness about the same as unobstructed sky.


    -- Hans Moravec
From: minsky@media.mit.edu (Marvin Minsky)
Newsgroups: sci.physics
Subject: Re: how do you do the one about an infinite mesh of 1ohm resistors ...
Date: 24 Jul 92 16:52:17 GMT
Organization: MIT Media Laboratory
Cc: minsky

In article <2798@ucl-cs.uucp> O.MostynOwen@cs.ucl.ac.uk writes:
>
>There's a problem I was told about years ago which I never managed to solve:
>
>You've got an infinite 2D grid if 1 ohm resistors. What's the resistance
>across 1 of them (no it's not 1ohm, 0 or infinity).
>
>              |                  |                   |
>         ------------1ohm-----------------1ohm------------
>              |                  |                   |
>              |                  |                   |
> .....      1ohm               1ohm                1ohm     .....
>              |                  |                   |
>              | A                | B                 |
>         ------------1ohm-----------------1ohm------------
>              |                  |                   |
>              |                  |                   |
>>
>I'd be grateful if someone laid this one to rest since it keeps on coming
>back to haunt me.

It's a superposition trick.  Imagine attaching a current source
between points A and B, and forcing 1 ampere through the circuit.
There's a theorem (I forget the name) which says that this is
equivalent to the sum of two separate experiments of forcing 1 amp
into A and of sucking 1 amp out of B.  The first experiment would push
1/4 amp into the resistor from A to B, and so would the second
experiment!  So we find that 1/2 amp flows through the resistor, hence
the voltage between A and B is 1/2 volt.  Then because R = E/I, we get
the resistance must be 1/2 volt over 1 amp at the terminals, so the
resistance is 1/2 ohm.  Wonderful example of a sort of circular reasoning.
Newsgroups: sci.physics
From: matmcinn@nuscc.nus.sg (Mcinnes B T (Dr))
Subject: The Modern Physicist in Calculus I
Organization: National University of Singapore
Date: Mon, 27 Jul 1992 05:40:53 GMT

TA: And here we have the graph of y = 1/x, x>0. As you can readily
verify, this is a perfectly well-behaved, continuous, indeed, infinitely
differentiable function on the open set (0, infinity).
Modern Physicist [excitedly] Clearly, we have here a SINGULARITY!
y=infinity at x=0. This is totally unacceptable!
TA: As I said, the domain is an open set. x=0 is excluded. There is
nothing remarkable about that.
MP: Nonsense! Next thing you'll be saying that there is nothing
remarkable about the SINGULARITY at the beginning of the Universe! Then
you will try to tell us that time is defined on an open set, and that
there is nothing remarkable about that either!
TA: Quite.
MP: No! Everybody knows that the prediction about the singularity shows
that "GR contains the seeds of its own destruction" [tm]. And now I
begin to suspect that the graph of y = 1/x proves that freshman calculus
also contains the seeds of its own destruction......

Moral: Time is defined on an open set. Spacetime has no singularities.
From: sichase@csa2.lbl.gov (SCOTT I CHASE)
Newsgroups: sci.physics
Subject: Re: "What's New" July-24-1992
Date: 29 Jul 92 18:40:36 GMT
Organization: Lawrence Berkeley Laboratory - Berkeley, CA, USA
Distribution: na
Reply-To: sichase@csa2.lbl.gov
NNTP-Posting-Host: 128.3.254.197
Summary: more hypocracy
News-Software: VAX/VMS VNEWS 1.3-4   

In article <1992Jul29.042544.7010@murdoch.acc.Virginia.EDU>, crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass) writes...
> 
>     How exactly does one quantify 'the amount of new engineering'
>     in a project comprised of components that have never been built
>     before?   With this in mind, how do you state that there is
>     more 'new engineering' in SSF vs. SSC.  Both sets of designers
>     have attempted to keep the technological risks of their 
>     prospective toys down.
> 

At least for the SSC, the design emphasized known technology specifically
so as to downplay the need to depend on "new engineering." That was crucial
to insuring timely construction.  Surely as an engineer you know that it
is always possible to choose from a wide variety of materials and techiques,
some of which have proven track records, and others, though they might
promise increased performance, pose the risk of cost and time overruns which
might defeat the purpose of the project.

Although I don't know exactly how to "quantify" these things, I certainly 
know how to judge two designs side by side to decide which one seems a 
safer design choice.

-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: bhoughto@sedona.intel.com (Blair P. Houghton)
Newsgroups: sci.physics
Subject: Re: A Modest Proposal
Date: 24 Jul 92 04:05:46 GMT
Organization: Intel Corp., Chandler, Arizona

In article <24830@dog.ee.lbl.gov> sichase@csa2.lbl.gov writes:
>But, IMHO, the real strength of this newsgroup is that it has hooks into
>almost all the major labs and universities in the US, and many around
>the world.  This usually means, for example, that almost any subject will
>be treated in an expert manner by someone who *really* knows the subject
>who comes out of the woodworks to set the record straight.  

Well, I'll never deny fully that such a situation exists, since it
is from this benefit that our funding exudes.  (If it was just a
netload of dirty GIFs and 2d-amendment rhetoric the NSF woulda shut
this puppy down after the first ten phonons hit Duke...)

However, it's not so clean as you might imagine.  We now lack one
of our most valued members, in the late person of Larry Lippman,
who, as Marvin Minsky pointed out, would have forgotten more about
chemistry than we know of our own gastronomic preferences, were
Larry prone to forgetting anything, which he weren't.  This is
merely an irrevocable example of the gaps in our roster.  More
often, the real deal is just too busy to notice the latest periodic
peak in the flux of argument.  And I've never seen anything
discovered by the net, just a lot of "Professor, it hurts when I
know this," "So, don't know that," sort of thing.

I don't even know if the NSA's labs have a net.connection
(Hi, General Scowcroft!).

Still, Robert Park isn't the only guy with a teletype (well,
maybe the only guy who still posts from it...).

So I'll go along with it.

I'll post an annual "News from the AMD Xerox Room" posting
with all the really *good* schematics Intel's published
in the 12 months preceding the preceding 12 months.

				--Blair
				  "Well, those I can piece together
				   from the annual shredding/newfs'ing
				   parties..."

Disclaimer:  I don't even remember where I parked my car,
most days; you think _I_ talk for Intel?
Xref: sparky sci.physics:12123 sci.philosophy.tech:2922 talk.religion.misc:13141
From: sichase@csa2.lbl.gov (SCOTT I CHASE)
Newsgroups: sci.physics
Subject: Re: Super Conducting Supercollider
Followup-To: sci.physics
Date: 31 Jul 92 19:08:48 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 <5568@lhdsy1.lahabra.chevron.com> rcj@lhdsy1.lahabra.chevron.com (R.C. Jones) writes:

>> What are the more scientific opinions about the value
>> of the Super Conducting SuperCollider program?

I will not get involved in this thread again... I will not get involved in 
this thread again... I will not get involved in this thread again... I 
will not get involved in this thread again...  Rustum Roy was a moron...
I will not get involved in this thread again... I will not get involved in 
this thread again...

-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: dk@imager (Dave Knapp)
Newsgroups: sci.physics
Subject: Re: Converting the masses
Date: 22 Jul 92 22:32:18 GMT
Organization: Laboratory for Experimental Astrophysics

In Article <1992Jul22.193837.18095@sfu.ca> palmer@sfu.ca 
(Leigh Palmer) writes:

> In order to illustrate my point, do you claim that a lump of
> condensed matter has a the same mass as the sum of the masses of
> its elementary constituents? Of course you don't.  That only
> begins the parade of difficulties attendant to using the currently
> fashionable definition outside its proper area of use.

> To further confuse the beginning physics student you could explain
> that the mass of that lump of matter is independent of its
> temperature.

  This caricature of the "currently fashionable definition of mass"
is pretty twisted.  Surely you can't be claiming that the use of
"rest mass" as "mass" implies that one must use the sum of
constituent masses to obtain the mass of an object?  If you are, then
how do you think particle physicists define the proton mass?  As the
sum of the masses of the constituent quarks?  Not likely.

  Hmmph.  I think I smell a straw man.  -- Dave


-- 
  *-------------------------------------------------------------*
  * David Knapp        dk@imager.llnl.gov       (510) 422-1023  *
  *            98.7% of all statistics are made up.             *
  *-------------------------------------------------------------*
From: jmc@SAIL.Stanford.EDU (John McCarthy)
Subject: Re: Low Tech is Best
Reply-To: jmc@cs.Stanford.EDU
Organization: Computer Science Department, Stanford University
Date: 22 Jul 92 21:37:27

In article <1992Jul23.033818.14931@usenet.ins.cwru.edu> bj368@cleveland.Freenet.Edu (Mike E. Romano) writes:

   Actually my original question is poorly worded.
   I am not an engineering major so I do not know the applicable formulas.
   Also my title is misleading and probably creates wrong impression.
   The physics problem is simply this:
   can a suitable wire transfer mechanical or work energy with less loss
   over a long distance (say a quarter mile) than an electric line of
   similar length?
   I am not stating that human labor is superior to machine labor, nor
   that we should return to the pre industrial era.
   -- 
	       Mike Romano     Univ. Calif. Berkeley

It seems to me that part of the question is whether energy conversion
is required at either end.  If so, the losses in the conversion(s)
are likely to exceed the losses in transmission.

In the electrical case, the losses can be made extremely low by using
a very fat cable.  At some point the interest on the capital investment
in the cable exceeds the saving from reducing ohmic loss.  I would suppose
that the usual cable sizes come close to this optimum.  Another
factor is the voltage used.  High voltages transmit energy with low
losses, but the conversion losses are likely to dominate unless the
energy is generated and used at a high voltage.

For very long distances (1,000 miles), it pays to convert the
electricity to very high voltage DC and convert it back again.
The lines taking electricity from the dams in the Pacific Northwest
to Central and Southern California are high voltage DC.

I don't see what the dominant losses would be in the mechanical
transmission of energy for 1/4 mile.  Some kinds of loss are

1. air resistance of the moving cable

2. flexing of the cable

3. bearing losses in the pulleys

I gather the Amish object to using electricity for religious reasons.

In my capacity as an Amish theological expert, I consider it not in
the spirit of the religion to get around its prohibitions by
introducing new-fangled mechancial devices.
--
John McCarthy, Computer Science Department, Stanford, CA 94305
*
He who refuses to do arithmetic is doomed to talk nonsense.
From: dlg47782@uxa.cso.uiuc.edu (Tegid Tathal)
Newsgroups: sci.physics
Subject: YAG laser wanted - I lost the post on the one for sale.
Date: 31 Jul 92 17:10:11 GMT
Organization: University of Illinois at Urbana


In a post not so long ago, someone was offering a YAG laser,used for sale.
I absentmindedly lost the post am interested if anyone knows of the post
of which I speak, or can give me the e-mail info, I would be very thankful.
Please e-mail responses.
Thanks.

Tegid.


*******************************************************************************
* "Many are the wand bearers, but few are the mystics."                       *
*                                                                             *
*   dlg@fourier.tam.uiuc.edu                                                 *
*       University of Illinois                                               *
*          Department of theoretical and applied mechanics                   *
*              129 Talbot Laboratory                                         *
*                  104 S. Wright St.                                         *
*                      Urbana, IL 61801                                      *
*                         (217) 333-0012                                      *
*******************************************************************************
From: mdd@nextc.Princeton.EDU.ampr.org
Newsgroups: sci.physics
Subject: Re: ZERO Nuclear impact (was: Is car pooling for real? etc)
Date: 24 Jul 92 22:13:51 GMT
Reply-To: mdd@nextc.princeton.edu
Organization: Princeton University
Originator: news@ernie.Princeton.EDU

No one seems to have mentioned this yet...There are other ways to  
distribute solar power besides using an electrical grid. Solar power can  
be used to convert water to hydrogen quite efficiently and the hydrogen  
could then be transported through an infrastructure similar to the natural  
gas infrastructure that already exists. End users would then burn the  
hydrogen. Or even better use it to power fuel cells. It is likely (I am no  
expert) that is a more cost effective approach to solar energy than  
erecting solar panels on the East coast, say. 

Another renewable energy source that doesn't contribute to global warming  
would be gasification of biomass. Biomass grown and harvested specifically  
for energy use can be turned into hydrogen and methane that can then be  
transported in pipelines and burned. There is no net increase in  
atmospheric CO2 if things are managed correctly. 

It seems pretty clear to me that people need to think about these new  
technologies. The picture of solar energy as a panel on every rooftop is  
somewhat outdated. New nuclear power is not much more than a stopgap  
measure, at least in its present form. And certainly any new nuclear  
plants should not be in the old style. Safer, smaller plants of uniform  
and well-tested design is the preferred direction. I seem to recall that  
there is only about 70 years worth of fissionable uranium to be found,  
although breeder reactors would be able to get around this shortcoming. 

In summary, there are several different alternative energy sources that  
are environmentally benign and could be quickly developed and implemented  
if we chose to vigorously pursue them. And, finally, there certainly can  
be nothing wrong with encouraging conservation. New building designs that  
can greatly reduce the amount of power used for heating and air  
conditioning is one area of active research. Conservation is certainly  
cheaper and more cost-effective than building new plants. Why else would  
power companies offer $30 million for an efficient, CFC-free refrigerator?

Well I have gone on enough so I'll stop here. 

Mark Doyle, Almost Ph(inishe)D.
mdd@nextc.princeton.edu
Newsgroups: sci.physics
From: crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass)
Subject: Re: "What's New" July-24-1992
Organization: University of Virginia
Distribution: na
Date: Wed, 29 Jul 1992 20:39:40 GMT

In article <25027@dog.ee.lbl.gov> sichase@csa3.lbl.gov writes:
>In article <1992Jul29.182755.426@murdoch.acc.Virginia.EDU>, crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass) writes...
>> 
>>     This 'new engineering' thread is probably not a fruitful thread
>>     to pursue since a 'safer design choice' is not well-defined
>>     in this context.  I 'know' that a space station can be put
>>     in orbit that will satisfy the performance objectives.  I do not
>>     'know' that such can be done for the SSC.  Which is 'safer'
>>     in this context.
>> 
>
>Well, the designers of the SSC claim that their design meets or exceeds all
>the design objectives.  Why would you doubt their claim, based upon zillions
>of hours of computer simulation, more than you would doubt the designers 
>of the space station?  

     This is actually the point.  Design 'risks' of the SSC arise from,
     among other things, never having made magnets of that performance
     and never having put it together before.  Design 
     'risks' of SSF arise from, among other things, never having put something
     like that together *in space*.  I 'know' that it can be put
     together on the ground.   Which is more 'risky'?

     *I* do not know, and I suggest that those here who claim or imply that 
     they do are mistaken.

                                  dale bass
--
C. R. Bass                                           crb7q@virginia.edu
Department of Mechanical and Aerospace Engineering
University of Virginia
Charlottesville, Virginia                            (804) 924-7926
From: sichase@csa2.lbl.gov (SCOTT I CHASE)
Newsgroups: sci.physics
Subject: Re: "What's New" July-24-1992
Date: 29 Jul 92 18:31:53 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 <1992Jul29.010055.3863@murdoch.acc.Virginia.EDU>, crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass) writes...
> 
>    NIH is being forced to fund study into chiropractry(?) along with the
>    other 'alternative medicine' approaches. 
> 
>    As far as astrology goes, I'd think that such widespread antiscientific
>    beliefs would be of great interest to those in the APS apparently
>    interested in scientific purity.  

Scientific organizations generally do, and should, only take political stands
when their specific expertise lends special credibility to their claims.
What does the APS know that every congressman doesn't already know about
astrology?  And what do they know more than the AMA about alternative
medicine?  It would be unethical for the leaders of the APS to put
themselves forward as experts on medicine, even if they *do* know enough
to judge this particular issue.  That's the role of the AMA.

I think that it is a credit to the APS, not a demerit, to point out that
they are selective in choosing issues on which to take a stand.  

It seems like dale would have bashed the APS one way or the other.  If they
said nothing, surely he would point out that they have no guts to stand
up for what they believe in.  And if they ever did get up to complain
about funding for chiropractry, he would point out that they were butting
their noses in where nobody wanted them.

-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: snyder@henry.ece.cmu.edu (John Snyder)
Subject: Re: What are those things called...
Organization: Physics Department, Carnegie Mellon University
Date: Fri, 24 Jul 1992 06:34:59 GMT

In article <1992Jul23.205300.7720@microplex.com> hsk@microplex.com (Harjeet Kalsi) writes:
>
>I know I've seen them in physics labs (including mine when I was in school) 
>but forgotten what this "box" with two antennas, that has a high
>voltage spark travelling between the antennas from bottom to top,
>is called.
>
>Also, does anyone have any instructions on how to make one?
>
>Please respond via e-mail or public forum if it's of general interest.
>Many thanks in advance.
>
>
>
>hsk@microplex.com


I believe that it's called a Jacob's Ladder.  It's interesting to note that
in any of the Star Trek episodes where Spock had to improvise equipment
from archaic (i.e. 20th century) technology, one of those was always
included in the rig.  As far as I know, they do not perform any electonic
function, but are rather a science-museum type demonstration piece, so
I have no idea what function they were supposed to perform for the 
time-travelling Star Trek crew.

I hope this helps

John
snyder@henry.ece.cmu.edu

Newsgroups: sci.physics
From: allenk@vex.ugcs.caltech.edu (Allen Knutson)
Subject: Why does 3D => fermions and bosons?
Organization: California Institute of Technology, Pasadena
Date: Mon, 27 Jul 1992 01:52:11 GMT

I posted something recently explaining why rotational symmetry causes there
to be wave-functions that change by only +/- 1 under 360 degree rotations.
But how does this mix with how the wave-function has to change when you
take two identical particles and switch them? After all, the two-particle
system doesn't have the SO(3) symmetry anymore, just O(2).

(And am I thinking right that "two identical particles" means "two
equivalent irreducible representations of the underlying symmetry group
of the physics"? And that people discovering additional quantum numbers
is equivalent to them extending their group? There seem to be so many
more books out there to explain math to physicists than physics to
mathematicians : -8 (						Allen K.
From: baez@ucrmath.ucr.edu (john baez)
Newsgroups: sci.physics
Subject: General Relativity/Quantum Cosmology mailing list
Date: 29 Jul 92 21:39:41 GMT
Organization: University of California, Riverside


There is now a preprint mailing list for the above subjects.
Send a message to gr-qc@xxx.lanl.gov with header HELP and no message body for
information.  
Newsgroups: sci.physics
From: Tom Pierce <pierct@rpi.edu>
Subject: WANTED: Concise text on Fourier Transforms
Organization: Physics Dept.
X-Useragent: Nuntius v1.1b1
Date: Wed, 29 Jul 1992 18:14:15 GMT

I'm trying to find a text on Fourier Transforms aimed at the intelligent
Physics student that is interested in applying them practically.  I'd
like a fair bit of examples, and clear, concise text.  Most of the books
I've read either pass them over with a "You should know this already"
attitude or go into deep mathematical theory.  I'm not partically
interested in their history, or what great aesthetic significance they
may have to ivory tower theorists.  I want to learn how to use them to
actually simulate (optical) processes.

Any help on this topic would be greatly appreciated.  If enough responses
come in I'll post a summary to the net for general use.  Please send any
responses to my individual email account:

pierct@rpi.edu

Thanks very much,
Tom Pierce
Physics Dept., RPI
Newsgroups: sci.physics