X-Message-Number: 5522
Date: Mon, 1 Jan 1996 18:51:24 -0800
From: John K Clark <>
Subject: Faster Than Light

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Relativity does not forbid anything from moving faster than light, only stuff 
that has mass or energy or carries information. Strangely, some things have 
none of these attributes, although calling them "things" may be stretching a
point. It's been proven experimentally that some quantum effects propagate 
instantly and for unlimited distances. One system can influence another 
system on the other side of the universe without the slightest delay, 
but it carries no information because the receiving system just changes from 
one apparently random mode to another, it's only when you compare the two
systems (and that can only be done at light speed or less) does the 
correspondence between the two systems become obvious. The 2 random modes 
have equal energy so energy is not transferred either.

A less spooky example could be found in the idea of Phase Speed.
I'm standing in the center of a huge hollow sphere 2 light years in diameter, 
I've been there for a long time and I'm holding a powerful LASER that makes a 
spot of light on the distant wall of the sphere one light year away. 
Suddenly, still holding the LASER and in the space of one second I make a 
complete 360 degree turn. Exactly 2 years later an observer standing at the
same place would see the spot move much faster than light, it would travel 
the entire circumference of the sphere, 2PI or 6.28 light years in only 
one second. No photon moved faster than light however, and no energy or 
information between any two points traveled faster than light. 

A photon of light moves at light speed and carries energy and information, 
a spot of light can move at any speed but carries neither energy nor 
information.
 

                                           John K Clark        

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