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From: Dale.Amon@H.CS.CMU.EDU.UUCP
Newsgroups: sci.space
Subject: Probes vs Large scopes
Message-ID: <533014214.amon@h.cs.cmu.edu>
Date: Fri, 21-Nov-86 22:30:00 EST
Article-I.D.: h.533014214.amon
Posted: Fri Nov 21 22:30:00 1986
Date-Received: Sun, 23-Nov-86 03:43:57 EST
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I find myself in disagreement with Paul on the value of an interstellar
flyby, but he does bring up an interesting point.

Let us assume there exists an earth like planet around another star
with interesting structures on it's surface, be they water, mountains,
cities, or what have you.

What are the theoretical limits to the distance at which they can be
seen by an optical scope? Are there quantum effects that will limit
resolution? How much effect does intersteller dust and gas between us
and the object have on theoretical resolution? What is the relationship
between the scope size and the distance to the interesting surface
feature?

Given that a scope could be built that could detect a city or town at a
distance of Alpha Centauri, what are the cost comparisons?

I don't expect to find a city anywhere nearby, but I expect that things
such as cratering and surface history of objects around other stars,
particularly of varied spectral class, would tell us very interesting
general things about planetary evolution, and would no doubt give us
some surprises. Is plate tectonics common? Is it truly dependent on the
presence of oceans? Is a large moon(s) helpful in driving it?

My gut feel is that it might be easier to build the probe. Not to
mention, it is as good a test bed for really advanced engines as just
about anything, and will probably grab the 21st century imagination
because it will prove that IT CAN BE DONE.

Once a probe proves it, it is only a matter of time (within 50-100 years of
the probe pictures coming back) before people do it. But then, the
people might well pass it up, as someone noted about obsolete
propulsion systems.

Gary: Too bad about the solar system picture. Maybe we need a high
inclination shot to get the inner solar system from 10 AU's or so over
the solar pole. Maybe ISPM could get an interesting shot, if it had
cameras. (Although it is not going to be all that high above the
ecliptic)