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From: Alfke.PASA@Xerox.ARPA
Newsgroups: net.sf-lovers
Subject: Re: Those inquisitive aliens
Message-ID: <3187@topaz.RUTGERS.EDU>
Date: Thu, 8-Aug-85 13:59:00 EDT
Article-I.D.: topaz.3187
Posted: Thu Aug  8 13:59:00 1985
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Organization: Rutgers Univ., New Brunswick, N.J.
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From: Peter Alfke 

Dave Newman (Newman.pasa@Xerox) writes:
>Any alien in the solar system will notice us on Earth!!! ...
>It is very easy to see that something is
>happening on Earth if you look at a night-time picture of North
>America; you can identify most of the major population centers by
>the size and approximate location of the blob of light that sits
>there.

From a low orbit (i.e. a LandSat satellite, from which we get those
pretty pictures) only.	 From the distance of the moon, such features are
invisible.  In fact, ALL signs of civilization (except for radio
emissions, of which enough has already been said) are invisible.

					--Peter Alfke