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From: brad@looking.UUCP (Brad Templeton)
Newsgroups: net.movies
Subject: Why shouldn't time travel leave you in the same spot?
Message-ID: <323@looking.UUCP>
Date: Mon, 12-Aug-85 00:00:00 EDT
Article-I.D.: looking.323
Posted: Mon Aug 12 00:00:00 1985
Date-Received: Sat, 17-Aug-85 05:59:58 EDT
References: <9793@ucbvax.ARPA>
Distribution: net.movies
Organization: Looking Glass Software, Waterloo, Ont
Lines: 19

Everybody goes on and on about how if you time travel, you should end
up way out in space because the Earth is whizzing around the sun.

Not quite true.  Aside from the rotation of the Earth about its axis,
the planet is in an inertial frame.  To suggest a time traveller would
appear where the Earth "was" implies some sort of absolute frame that
the planet moves in.

So in theory, if you come back at the same siderial time of day that
you left, you would arrive at the same place.

Of course, it's probably true that photon pressure and solar wind make
the orbit of the Earth deviate slightly from an inertial frame.  Does
anybody know by how much?

A time travel story where they claim they can only arrive at the same
spot if they pick the exact time of day - that would impress me.
-- 
Brad Templeton, Looking Glass Software Ltd. - Waterloo, Ontario 519/884-7473