HDTenEightyP/NetNews huggingface dataset:
From: lizi@ocf.berkeley.edu (Cosma R. Shalizi)
Newsgroups: rec.arts.sf.science
Subject: Lasers vs. Radiators
Date: 8 Apr 1992 23:17:12 GMT
Organization: Vampire Research Group at Berkeley :)
Distribution: usa
NNTP-Posting-Host: tsunami.berkeley.edu

In article <1992Mar13.205505.6345@helios.physics.utoronto.ca> neufeld@helios.physics.utoronto.ca (Christopher Neufeld) writes:
>   The question was what sort of efficiency could you get by pumping a
>laser for a photon rocket. I pointed out that you could get the same
>efficiency as you could get by just running the electric current through a
>heating coil behind a shadow mask on the back of the spacecraft, so the
   I realize I'm coming in on this thread late, and it may have been flogged
to death with a wet noodle already, but there _is_ a reason
lasers are more efficent. Namely, all the light is of the same frequency
(monochrome) and usually all in phase (polarized) so you don't get
destructive interference. Setting a newspaper on fire with a 10W laser
is trivial. Doing it with a 10W light bulb (non-polarized, polychrome
light) requires substantial patience. 
   Besides, the problem with heat radiation is that you need surfaces
perpendicular to the direction you want thrust - i.e. either an
extremely hot and small radiator, or a very wide and non-molten one. You'd
also need to rig it so its hottest _away_ from the body of your ship, other-
wise it would act as a break (hey, that might be useful...). To do this,
you need to expend more energy (the source of the heat you dump into the 
radiator is in the ship) or the 2nd law goes into screaming fits.
To get anything useful out of it at all you'd need to have a steep temp-
erature gradient, otherwise the thrust from the two sides would almost
exactly cancel out.
   This is starting to sound decidedly less simple.
   Lasers don't have these problems.
   Of course, if I'm wrong, flame me and feed me to a kzin (no sense giving
them a meal they'd _like_).
Cosma Shalizi (lizi@ocf.berkeley.edu)
physicist in training & VP of Campus Crusade for Cthulhu (for which
I _do_ speak)
"St. Isaac of the Robots, pray for us now and when psychohistory becomes
personally irrelevant."
From: mjg51721@uxa.cso.uiuc.edu (Michael James Gebis)
Subject: Re: Psychohistory
Organization: University of Illinois at Urbana
Date: Tue, 14 Apr 1992 22:22:39 GMT

I seem to remeber a quote about this...either by Isaac himself, or by some
other relatively famous person....It was something about since foundation was
written well before chaos theory, it is no wonder it seemed believable at the
time.
	(Yes, I can hear you all say 'gee whiz Mike, you sure are specific'
	Hopefully, somebody else heard this too and can elaborate
	:)

Mike Gebis  mjg51721@uxa.cso.uiuc  OR  m-gebis@uiuc.edu
"AIM MY SMILING SKULL AT YOU"
From: Shinji.Kono@newcastle.ac.uk (Shinji KONO)
Newsgroups: rec.arts.sf.science
Subject: Re: Psychohistory
Date: 14 Apr 92 23:51:00 GMT
Organization: University of Newcastle upon Tyne, UK NE1 7RU

In article <1992Apr13.171823.27610@murdoch.acc.Virginia.EDU> abb3w@fulton.seas.Virginia.EDU (Arthur Bernard Byrne) writes:
>    Hari Seldon: Well, my skills are not unique... 

But he was already in unique position at that time.

To reduce 15,000 dark years to 1500 years, he needs a trick. The function
of 2nd Foundation is not only maintaintenace of 1st Foundation's development
but also changing the humanity itself.

Without 2nd Foundation's support, 1st Foundation is a candidate of 2nd
Empire in 15,000 dark years in my opnion. 1st Foundation's 2nd Empire will
be very close to the first one, and it will fall down like the first one.

People in 2nd Foundation is very special, out of psychohistorical
assumption.  They are not human in some sense.  In 2nd Foundation's 2nd
Empire, 1st Foundation prepares physical representation which is very
much like original Empire, but it will never torn apart because of 2nd
Foundation's control. That the another reason why Dr. Asimov wrote
Foundation's Edge.

Of course always, there is another....
-- 
Shinji Kono @ Computing Laboratory, University Newcastle upon Tyne
kono@csl.sony.co.jp                     Room: 616 Claremont Bridge
from Sony Computer Science Laboratory, Inc, Japan.
From: mjg51721@uxa.cso.uiuc.edu (Michael James Gebis)
Newsgroups: rec.arts.sf.science
Subject: Re: Dyson Sphere
Date: 11 Apr 92 18:49:02 GMT
Article-I.D.: ux1.1992Apr11.184902.593
Organization: University of Illinois at Urbana

If I was an alien race (and who's to say I'm not?), and I was intent on building
a Dyson sphere, this is what I'd do:  I'd first make a sphere with the top and
bottom cut off.  This would basically be a REALLY thick ringworld.  (A
braceletworld?)  I'd also set it spinning, so as to prevent it from collapsing.
But this wouldn't satisfy me...I'd say, "I want a Dyson SPHERE, not a Dyson
cored apple!"  I would then build another braceletworld, just a tad bit bigger,
but with the holes pointing 90 degrees to the original world's.  This way, I'd
capture all of the sun's energy!  I'd also set THIS one rotating, perpendicualar
to the first one.
	You, being a logical human being, might say, "That's very impractical.
The second world is hardly capturing any energy at all, since most of it is
hidden behind the first world."  But I would just shrug, knowing that a Dyson
sphere IS impractical, and the only reason I'd want one is for asthetic reasons.



	Niven's ringworld is the predecessor to a Dyson Sphere.  But what's a
predecessor to a ringworld?  Well, first, you make about 100 equal sized planets
equally spaced about the sun, all occupying the same orbit.  Then, to make
transportation between the sub-planets possible, you link them with tubes 
capable of transporting a train-like vehicle between two adjacent worlds.

			O--O
		      /      \
		     O   **   O
		     :  ****  :
		     O   **   O
		      \     /
			O--O

	The name of this pre-ringworld?  Necklaceworld, of course!

Mike Gebis  mjg51721@uxa.cso.uiuc  OR  m-gebis@uiuc.edu
"AIM MY SMILING SKULL AT YOU"
Xref: sparky rec.arts.sf.science:1379 sci.physics.fusion:961 sci.engr.chem:207
From: szabo@techbook.com (Nick Szabo)
Newsgroups: rec.arts.sf.science,sci.physics.fusion,sci.engr.chem
Subject: Re: Magnetic sails
Summary: Use magsails to manipulate space plasmas?
Date: 7 Apr 92 08:11:44 GMT
Distribution: rec
Organization: TECHbooks of Beaverton Oregon - Public Access Unix

I'm interested in large, lightweight coils for their ability to manipulate
space plasmas.  For example, there are many chemical reactions
that occur in the tails of comets, driven by solar protons, UV, etc.
Here is a list of the processes (from Whipple) with examples:

Photodissociation: [hv + H2O -> H + OH]
Photoionization: [hv + CO -> CO+ + e]
Photodissociative ionization: [hv + CO2 -> O + CO+ + e]
Electron impact dissociation: [e + N2 -> N + N]
Electron impact ionization: [e + CO -> CO+ + 2e]
Electron impact dissociative ionization: [e + CO2 -> O + CO+ + 2e]
Positive ion-atom interchange [CO+ + H2O -> HCO+ + OH]
Positive ion-charge transfer [CO+ + H2O -> H2O+ + CO]
Electron dissociative recombination [C2H+ + e -> C2 + H]
3-body positve ion-neutral association [C2H2+ + H2 + M -> C2H4+ + M]
Neutral rearrangement [N + CH -> CN + H]
3-body neutral recombination [C2H2 + H + M -> C2H3 + M]
Radiative electronic state deexcitation [e + O(1D) -> O(3P) + hv]
Electron impact electronic state quenching [e + O(1D) -> e + O(3P)]
Radiative recombination [e + H+ -> H + hv]
Radiation stabilized positive ion-neutral association [C+ + H -> CH+ + hv]
Radiation stabilized neutral recombination [C + C -> C2 + hv]
Neutral-neutral associative ionization [CH + O -> HCO+ + e]

These reactions might be manipulated to produce useful products.  
For example, we might separate C13 out of a carbon-rich plasma and 
vapor-deposit it as diamond. I don't know how we could concentrate and 
collect the plasma with sufficiently lightweight coils, though.  How much 
more efficient is mass spectroscopy over 100's of kilometers in a vacuum? 


-- 
szabo@techbook.COM  Public Access User --- Not affiliated with TECHbooks
Public Access UNIX and Internet at (503) 644-8135 (1200/2400, N81)
From: v118qpx9@ubvmsb.cc.buffalo.edu (BYTEMAN, OF COURSE)
Newsgroups: rec.arts.sf.science
Subject: Re: Dyson Sphere
Date: 9 Apr 92 16:43:00 GMT
Organization: University at Buffalo
News-Software: VAX/VMS VNEWS 1.41

In article <1992Apr7.183343.18093@murdoch.acc.Virginia.EDU>, jes2x@fermi.clas.Virginia.EDU (John Sommerville) writes...
>Could somebody tell me exactly what a Dyson sphere is, and in which books
>one plays a large part?  I would be most grateful.

Larry Niven has a collection of short stories call _A Hole in Space_.
I believe he has a short speculation piece on a variety of worlds that could be
built for exploration, living space, etc.  One of them was a Dyson sphere; he
even went so far as to describe one spinning to produce the necessary gravity! 
Very fascinating "article."

 ------------------------------------------------------------------------------
| Sean Souva                      |                                            |
| V118QPX9@UBVMS.CC.BUFFALO.EDU   |            JESUS SAVES SINNERS!            |
|       (Smile! I'm a nice guy!)  |(and redeems them for valuable cash prizes) |
|                                 |                                            |
 ------------------------------------------------------------------------------
Newsgroups: rec.arts.sf.science
From: jdnicoll@watyew.uwaterloo.ca (James Davis Nicoll)
Subject: Re: Cherryh's technology (was: SF about doing science ?)
Keywords: Don't read _Twistor_
Organization: University of Waterloo
Date: Thu, 16 Apr 1992 21:00:04 GMT

In article <1992Apr16.153642.17830@ux1.cso.uiuc.edu> mjg51721@uxa.cso.uiuc.edu (Michael James Gebis) writes:
>s5223927@titan.ucc.umass.edu (Daniel Lescohier) writes:
>
>>In article <1992Apr14.041927.16381@ccu1.aukuni.ac.nz> ecmtwhk@ccu1.aukuni.ac.nz (Thomas Koenig) writes:
>>>
>>>One other thing which peeves me are the speed and acceleration.
>>>Accelerating at 10 g's will not get you up to light speed in a matter
>>>of minutes.
>
>>	True.  It would take about 35 days to get to light speed at 10g
>>acceleration (3*10^8 m/s / 100 m/s^2 = 3*10^6 s = approx. 35 days.)
>>That's extremely fast compared to today's standards, however.
>
>Actually, if you believe Einstein, it would take FOREVER to reach light speed.
>(But I haven't read the book, so if she doesn't belive Al, don't flame)

	35 days, as measured on the ship, will get you to ~0.76 C.

	Cherryh has NAFAL ships in the early interstellar period, so
she does kinda acknowledge SR and GR. I think 'Heavy Time', which I
have not read, deals with that period.

	Any idea how the early interstellar economy worked, anyone? What's
worth investing the energy to get up to NAFAL that one couldn't duplicate
for less energy at home? Information cold be sent via EMR, which would be
cheaper.

							James Nicoll
Newsgroups: rec.arts.sf.science
From: gmartin@zia.aoc.nrao.edu (George Martin)
Subject: Re: Dyson Sphere & Ringworlds
Organization: National Radio Astronomy Observatory, Socorro NM
Date: Thu, 9 Apr 92 06:13:23 GMT

In article <1992Apr9.011209.17690@minyos.xx.rmit.oz.au> s861022@minyos.xx.rmit.oz.au (Harry the Dirty Dog) writes:

[In a thread about Dyson Spheres and Niven's Ringworld]
>
>Hasn't anyone heard of Orbitsville and Orbitsville Departure by Bob Shaw.
>Now that most definately features the idea of a Dyson Sphere.

I think that _Orbitsville_ appeared in print a very few months after
_Ringworld_ (and I think in one of the magazines but I am not sure).
Although there was no way it could have been, Shaw had to defend himself
against charges of plagiarism.  (So I seem to remember anyway!!!!)
-- 
George Martin
Systems Analyst                     NRAO/VLA                  Socorro NM
Internet: gmartin@zia.aoc.nrao.edu
"Skating away on the thin ice of the new day."  (Ian Anderson)
From: Shinji.Kono@newcastle.ac.uk (Shinji KONO)
Newsgroups: rec.arts.sf.science
Subject: Re: Psychohistory
Date: 11 Apr 92 20:31:44 GMT
Organization: University of Newcastle upon Tyne, UK NE1 7RU

In article <1992Apr10.201851.3739@spss.com> markrose@spss.com (Mark Rosenfelder) writes:
>Refutations: Read _War and Peace_, particularly the philosophical section
>at the end.  In brief, Tolstoy argues that human events *are* caused
>by masses of people.  (Of course, maybe both of you are wrong.)
>Comments:
>   Hari Seldon: My theory is that when you get enough people together
>     history is determinate.  I say the Galactic Empire is going to
>     fall apart for 30,000 years.  However, with careful management
>     this can be reduced to 1000 years.

The cause of history is depends on a product of time and masses of people.
History is predictable by psychohistory, but not necessarily deterministic.
You see the way of history prediction in "the second foundation". It is 
different from prediction book, it is a complex formula database. If you
have a large number of people in uniform caltures, these predictions become
simple. This is the first theorem.

Asimov find a need of *very* long life single person to change history.
So he wrote "Robots and Empire". Very logical. And he notices inevitable non-
deterministic nature of psychohistorical prediction, so he wrote "The edge of
the foundation". Clearly, he turns non-determinitc history into the free will
of the unified mind of masses of people, and it makes the whole stories
complete.

Of course, we don't know the detail of the unifed mind. It must not be a
totalitarian world. We have to investigate it. I think this is what Dr.
Asimov left to us to solve. 

Thank you, Dr. Asimov. We have all your idea.  Let us help to make it
real.
-- 
Shinji Kono @ Computing Laboratory, University Newcastle upon Tyne
kono@csl.sony.co.jp                     Room: 616 Claremont Bridge
from Sony Computer Science Laboratory, Inc, Japan.
Newsgroups: rec.arts.sf.science,alt.cyberpunk.tech,alt.cyberspace
From: mjg51721@uxa.cso.uiuc.edu (Michael James Gebis)
Subject: Re: Virtual reality, the brain, and high-speed modems.
Organization: University of Illinois at Urbana
Date: Sat, 11 Apr 1992 18:54:55 GMT


After mulling this over a bit, I _STILL_ don't think it's impossible...just
pretty difficult.
        1)  It would probably be nearly impossible to simulate the entire
input from the nervous system, so some other method would probably be used.
(Then again, 15 years ago, people thought Atari 2600 was hi-tech...who knows
what lies ahead.)
        2)  Much more information about the brain would have to be known.
The interface would also have at least part of it inside of the brain....this
would allow the interface to tell the brain, "You see a car there," as 
opposed to sending a total graphic representation to the brain.
        3)  A good AI processor would help in this situation.
        4)  Implantation of the device would requite advanced nanotechnology.
(Or, I suppose, you could undergo surgery that lasted a significant portion
of your life, as doctors painstakingly manipulated billions of neurons.)
        5)  If I wanted to write a story with an interesting twist, I'd make
it so that the interface would be implanted in the womb, as the brain was        
developing.  Why?  Because the nanos would also make sure the brain developed
in a way that insured the technology would work.  The philosophical
implications of altering a child could make a story, somehow.
        6)  If I wanted to justify some already existing stories, where VR is
addicting and even life threatening, I'd do this:  The interface doesn't         
need input to keep autonomous body functions going...in other words, it 
keeps the heart beating, it breathes for you, and it does all of the boring
bodily functions.  A user's brain soon becomes acclimated to NOT doing this
stuff.
        7)  All those stories in which the hero 'plugs' into a terminal with
an interface not much more complicated than a headphone jack are probably not
very realistic.   Also, there's no WAY my 2400 baud modem could work...I'd 
need AT LEAST a 9600 with v42.bis and MNP 5.  (Yes, this is my attempt at 
humor...)
	8)  There would have to be a REALLY useful application for VR for this
this type of thing to be worthwhile, and I personally can't think of anything
that would justify the effort.
	9)  Anything I forgot?

Mike Gebis  mjg51721@uxa.cso.uiuc  OR  m-gebis@uiuc.edu
"AIM MY SMILING SKULL AT YOU"
Newsgroups: rec.arts.sf.science
Subject: Re: Kevlar Balloon Space Station mk II
From: jjfink@skcla.monsanto.com
Date: 16 Apr 92 09:30:41 GMT
Organization: Searle, Skokie, IL
Nntp-Posting-User: fleet

In article <1992Apr16.005054.39402@kuhub.cc.ukans.edu>, 2frssprout@kuhub.cc.ukans.edu writes:
> To summarize the issue:  Why not use Kevlar balloons as space station hulls?
> 
> Problems:  Radiation (hard, soft, and electromagnetic), affecting both the
>            Kevlar (James William Stepanek claims polymers tend to break down
>            under intense UV) and the people (EM and hard stuff).  
> 
> Response:  Fix UV and EM problems by an outside layer of aluminum foil?
> 
> Another thought:  - Space is cold.  Station is warm.  Brittleness problems?

Probably, this has been said, but after you inflate the darn baloon, spray
the inside or outside with concrete made from lunar soil.  It's a lot
cheaper to move than earth stuff, is insulating, durable, etc.

Anybody got a blueprint of a microgravity cement mixer?
From: nickh@CS.CMU.EDU (Nick Haines)
Newsgroups: rec.arts.sf.science
Subject: Re: Alternate Universes
Date: 17 Apr 92 17:36:50 GMT
Article-I.D.: VOILA.NICKH.92Apr17123650
	<1992Apr16.231955.5421@onetouch.COM>
Organization: School of Computer Science, Carnegie Mellon University
Originator: nickh@VOILA.VENARI.CS.CMU.EDU

In article <1992Apr16.231955.5421@onetouch.COM> csmith@onetouch.COM (Craig Smith) writes:

   [in answer to Steve Albany's question, the expansion of the
	universe is like a balloon inflating]

   Now, if I interpret your question correctly, you are asking what is inside
   the balloon and/or outside the balloon.  Am I right?

   The answer is: No one knows, and speculations abound, most of which do
   not effect this universe.  The main result of the analogy to the balloon
   is that our 3-D universe exists in a 4-D space (at least) and we really
   are not sure what is "blowing it up" (no, it is not the force of the BB,
   since a force in 3-D cannot cause changes in other directions, unless a
   direct relationship exists between space and matter/energy.  Any theories
   on that?). Anyone have speculations on what is blowing up the universe?

Well, you do not actually need other physical dimensions (the `4-D
space') to allow that the universe is curved. In our world, one cannot
have curved objects without another dimension to `curve in', but
the Universe/balloon analogy starts to break down. The `curvature' of
space is just a tensor equation---it need not imply other dimensions.

Nick Haines nickh@cs.cmu.edu
From: bg413893@longs.LANCE.ColoState.Edu (Brian Grossman)
Newsgroups: rec.arts.sf.science
Subject: cloning in Where Late the Sweet Birds Sang
Keywords: cloning clones social_implications
Date: 8 Apr 92 00:07:00 GMT
Article-I.D.: yuma.1992Apr08.000700.49016
Reply-To: bg413893@lance.colostate.edu
Followup-To: rec.arts.sf.science
Organization: Engineering Network Services, Colorado State University

Hi all,

For my medical anthropology class I have to write a term paper.  I have
secured permission to use the clone society described in Kate Wilhelm's
_Where Late the Sweet Birds Sang_ so long as I can show that her
extrapolation of cloning science is "reasonable".

The problems I find are these:  for each successive generation of
clones there is a corresponding degeneration in fertility and mutations
are increasingly prevalent.

At the fourth or so generation, fertility begins to rise but mutations
make survival for any individual clone precarious.  (It sounds to me
like cells are having a difficult time differentiating, leading to high
incidence of cancer-like problems.  Perhaps this is also the cause of
increased fertility?)  By the sixth generation, there is almost zero
survival.

I have been able to find general references to "mutations" from what
might be called data transmission problems.

What I need are specific references that address these generation
problems.  Does anyone out there have the background for this, or does
anyone remember running across any texts or articles that discuss
something similar?

It doesn't need to be technical (I need to be able to follow it ;); it
just needs to give an indication her extrapolation is reasonable.  The
main focus of the paper is on the cultural effects.

Send me email or post to rec.arts.sf.science - I don't care.


Brian Grossman

	Sig? sig?  Here sigsigsig!

    Internet:  bg413893@longs.lance.colostate.edu
    UUCP:  ...ncar!boulder!ccncsu!longs.lance.colostate.edu!bg413893
From: luther@ohstpy.mps.ohio-state.edu
Newsgroups: rec.arts.sf.science
Subject: Re: Parallel Universes
Date: 16 Apr 92 16:44:07 GMT


  As a number of people have pointed out the Many-Worlds interpretation of
Quantum Mechanics is just that - an interpretation of the results of QM
experiments.  It in no way differs in the experimental predictions it makes
from any other "interpretation" of QM such as the "standard" Copenhagen method
or the transactional interpretation.  There is no way to decide which is
"better" by experiment.  Each has its pluses and minuses as a method of
thinking about what "happens" in QM.
  It is important to understand that the Many-Worlds idea is based on the
assumption that there is no method by which the different Universes can
communicate with each other.  This, of course, makes for lousy SF plots so most
writers just ignore this problem.  An example of a plausible, (though
physically incorrect), use of the Many-Worlds interpretation is the book by
Hogan call The Proteus Experiment(?).  (Not positive on the title.)  In fact,
if memory serves he even has a brief discussion of the real Many-Worlds model
in an appendix to the novel.  Actually the book is very entertaining if you 
like the sort of hard core SF that Hogan writes.

                                        -Bryan Luther

The Ohio State Univ. Physics Dept.               Luther@mps.ohio-state.edu
Los Alamos Meson Physics Facility                luther@lampf.lanl.gov
-------------------------------------------------------------------------------
Newsgroups: rec.arts.sf.science
From: mvp@hsv3.uucp (Mike Van Pelt)
Subject: Re: Dyson Sphere & Ringworlds
Organization: Video 7 + G2 = Headland Technology
Date: Thu, 9 Apr 1992 20:32:02 GMT

In article <1992Apr8.205529.2374@ux1.cso.uiuc.edu> mjg51721@uxa.cso.uiuc.edu (Michael James Gebis) writes:
> ... I came up with 9.327x10^9 N/mm^2 (Yup, that's square MILLImeters)....
>equivalent to a millimeter thick thread holding up 2.1x10^10 lbs.

Now you know why Niven felt compelled to give up on 'real-world' 
materials and invent scrith, which whatever its tensile properties
are, stops 40% of neutrinos.
-- 
Mike Van Pelt          | It was a typical net.exercise -- a screaming
Headland Technology    | mob pounding on a greasy spot on the pavement,
mvp@hsv3.lsil.com      | where used to lie the carcass of a dead horse.
...ames!vsi1!hsv3!mvp 
Newsgroups: rec.arts.sf.science