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From: chrisa@azure.UUCP (Chris Andersen)
Newsgroups: net.physics
Subject: Re:  re long scissors
Message-ID: <275@azure.UUCP>
Date: Sun, 16-Jun-85 04:30:50 EDT
Article-I.D.: azure.275
Posted: Sun Jun 16 04:30:50 1985
Date-Received: Tue, 18-Jun-85 04:29:23 EDT
References: <274@sri-arpa.ARPA>
Organization: Tektronix, Beaverton OR
Lines: 34

> From:  mikes@AMES-NAS.ARPA (Peter Mikes)
> 
>  The fundamental problem with wery long scissors is an ~ implict assumption ~
>  that blade is a rigid body. a rotating rigid body -- a sweep of a blade, 
>  lead to superluminal if size is large enough. But how do you define a rigid
>   body in a Lorentz covariant form ??

Okay, how about this for a better analogy:

Have you ever been to the beach and just sat there and watched the waves?
If you have you may have noticed that every now and then, two waves will
come in at the same time.  One will be tilted at a slight angle to the
other so that they can be distinguished from each other.  Like this:


                 \\\\				////
		      \\\\		   ////
			   \\\\       ////
			        \***/
			    ////     \\\\
                       ////       |       \\\\
				  |
				  V  Direction of beach and waves motion


The point where the stars are is the intersection of the two waves.
Now the point to be made by all this is that while the speed of the waves
through the water is limited to a certain value (what that is I don't know),
the speed of the point of intersection can be *greater* then that limiting
speed.

If you extend this to two wave fronts of light at an angle greater then 0
to each other, there point of intersection is travelling greater then
the speed of light.