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From: KFL@AI.AI.MIT.EDU ("Keith F. Lynch")
Newsgroups: net.space
Subject: Observing Dyson spheres
Message-ID: <[AI.AI.MIT.EDU].22502.860330.KFL>
Date: Sun, 30-Mar-86 12:23:21 EST
Article-I.D.: <[AI.AI.MIT.EDU].22502.860330.KFL>
Posted: Sun Mar 30 12:23:21 1986
Date-Received: Tue, 1-Apr-86 08:14:17 EST
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    From: ucdavis!ucrmath!hope!corwin@ucbvax.berkeley.edu (John Kempf)

    Interesting idea about the aluminum foil.  I had not considered
    just a shell, only a fully habitable sphere.

  The original idea was that the sphere would be many relatively small
asteroid-like objects.

    As far as visuals go, I was picturing things along the lines of a rotating
    flashlight from a half built sphere, to a strobe star from a partial sphere
    started from several locations.

  It would probably be built more or less all around the star at once,
and gradually become denser as more and more colonies, farms, and
factories are built, until finally none of the sunlight escapes into
interstellar space as all of it is intercepted.  Much like satellites
around the Earth (except that nobody expects satellites to become so
prevalent that they block all sunlight and moonlight from reaching
Earth).
  Of course it is possible that it might be built in the way you
describe, though it sounds pretty unstable to me.  And if it is
suspended by light pressure, it would not be rotating.  We would
either see the star or not depending on which way the hemisphere
happened to face.
  Probably what we should be looking for are room temperature IR
stars, stars that are unusually dim, stars that are getting rapidly
(on an astronomical timescale) dimmer, stars that do vary in
brightness in some hard to explain way, and of course anything else
unusual looking.

    Definately agree with launching more satellites and/or observatories,
    but why limit it to IR? Wouldn't radio also be a sign of civilization?

  Only if the aliens use strong but poorly aimed radio signals for
communications or some other purpose.  A more advanced technology
might consider radio obsolete.  But unless we seriously misunderstand
thermodynamics, any civilization which uses massive amounts of energy
for anything at all will have to radiate enormous amounts of infrared
into interstellar space.
								...Keith