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From: rdp@teddy.UUCP
Newsgroups: net.space
Subject: Re: Speed of Light and beyond
Message-ID: <938@teddy.UUCP>
Date: Mon, 15-Jul-85 17:09:09 EDT
Article-I.D.: teddy.938
Posted: Mon Jul 15 17:09:09 1985
Date-Received: Sat, 20-Jul-85 07:49:33 EDT
References: <1776@mordor.UUCP> <5602@utzoo.UUCP>
Reply-To: rdp@teddy.UUCP (Richard D. Pierce)
Organization: GenRad, Inc., Concord, Mass.
Lines: 34

In article <5602@utzoo.UUCP> henry@utzoo.UUCP (Henry Spencer) writes:
>> I know this is impossible, but what would happen if...
>> 
>> A ship could exceed the speed of light?  When the space shuttle crosses the
>> sound barrier, there is a sonic boom.  If it were possible to cross the
>> "light barrier", what phenomenon would result?
>
>A lot of heart attacks in the physics community, for one. :-)
>
>More seriously, as I recall it, the basic answer to this from relativity
>(if we ignore tachyons, which are a messy case) is "does not compute".
>Faster-than-light speeds involve logical contradictions (notably, loss of
>the normal cause-and-effect relationship) according to special relativity.
>This being the case, the theory basically cannot give coherent predictions
>about such a situation.
>
>I'd be very interested to hear this contradicted by somebody who knows
>more about the subject...
>-- 

In fact, under the right conditions, one can achieve "faster than light"
travel. While on cannot exceed a certain velocity "c" (2.99 x 10^8 m/s),
the velocity of propogation of light through matter is somewhat less than
this inviolable "c". For example, (if my memory serves me) light travels
about 30% slower in water than it does in a vacuum. Under this circumstance,
something which travels faster than that (but still MUST be less than "c")
will, in fact, produce the light equivalent of a sonic boom, known as
Cerenkov radiation. This is a shock wave which travels outward in a cone
(whose included angle is proportional to the ratio of the speed of light
in the media to the speed of the particle).

Note that no violation of any physical law occurs. Nothing can travel
faster than the sacred "Speed of Light" , which is the speed of light
absent of any influences (matter).