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From: krueger@uiuccsb.UUCP
Newsgroups: net.physics
Subject: Re: long lever - (nf)
Message-ID: <2520@uiucdcs.UUCP>
Date: Wed, 3-Aug-83 22:32:18 EDT
Article-I.D.: uiucdcs.2520
Posted: Wed Aug  3 22:32:18 1983
Date-Received: Sat, 6-Aug-83 08:11:16 EDT
Lines: 24

#R:uiucdcs:24400033:uiuccsb:10800001:000:925
uiuccsb!krueger    Aug  3 15:13:00 1983

20 years.  My line of reasoning:

Assume Mr. A and Mr. B can see one another (using telescopes or something).
Let's also assume that if Mr. A moves his end of the lever at all, Mr. B can
see exactly how far Mr. A's end moved.

Here's the crucial assumption:  The forces holding the lever together travel
no faster that the speed of light.

Then, when Mr. A moves his end of the lever, both the image of the motion and
the lever motion proceed towards Mr. B., with the image of Mr. A's end
movement probably beating out the force propogation.  It takes 10 yrs for
Mr. B to see Mr. A move his end, and he sees some rotation at the pivot some
time later.  If Mr. B sends his laser signal when he sees Mr. A move, Mr. A
will see the laser 10 yrs later.  10 + 10 = 20 (<- difficult calculation).

				I hope I'm not making a fool of myself,
				Physics was a long time ago for me.

				Jon Krueger,
				...!pur-ee!uiucdcs!krueger