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Path: utzoo!utcs!mnetor!fred
From: fred@mnetor.UUCP (Fred Williams)
Newsgroups: net.physics
Subject: Re: "speed of light" puzzle
Message-ID: <592@mnetor.UUCP>
Date: Wed, 15-May-85 09:18:51 EDT
Article-I.D.: mnetor.592
Posted: Wed May 15 09:18:51 1985
Date-Received: Wed, 15-May-85 10:20:58 EDT
References: <1720@ut-ngp.UUCP>
Reply-To: fred@mnetor.UUCP (Fred Williams)
Organization: Computer X (CANADA) Ltd., Toronto, Ontario, Canada
Lines: 28
Summary: 

In article <1720@ut-ngp.UUCP> graner@ut-ngp.UUCP (Nicolas Graner) writes:
>
>I have a laser on a turntable in such a way that the beam falls on
>the moon during each revolution. If my laser rotates at omega
>rad/s and the moon is at distance D, the spot moves on the moon
>at speed V = omega*D. Since I can make omega as big as I want,
>V can be made very big, and certainly much more than C. (e.g.
>with D ~ 300,000km and omega = 10rad/s, a very gentle speed,
>V = 3,000,000km/s = 10*C)
>
>How can anything move at 10*C without violating relativity ?

	The 'thing' that is moving is not a mass object. It is
	not even an energy object, (ie a photon). It is only
	an image and hence not bound by the restriction of the
	maximum speed of 'c'.

Cheers,		Fred Williams.

PS. By the way, if you want another relativistic puzzle,
consider the following,(I'll post the answer in a few days
after I've had a chuckle):

	If the speed of light is constant in all reference frames,
how come we can see doppler shifts?

	This is a good exercise in learning how to apply laws
	such as the conservation of energy.