Re: FTL transmission?

From: Spudboy100@aol.com
Date: Thu Jun 01 2000 - 00:09:19 MDT


I wonder what the effect, then would be of a FTL transmission that could only
work over tens of millions, or several billion lightyears; but non functional
any closer then that? Should we listen for messages eminating from the
distant future?

In a message dated 5/31/00 10:13:18 PM Pacific Daylight Time, hal@finney.org
writes:

<< According to relativity theory, if you can communicate faster than light
 in an arbitrary inertial reference frame, you can communicate backwards
 in time.
 
 The reason is because of the relativity of simultaneity. Two events
 which happen at the same time in one reference frame will happen at
 different times in another frame at motion with respect to the first.
 
 Someone in a spaceship zooming past the earth could use his FTL
 communicator to send a message from the earth to the moon which
 arrived 1.2 seconds before it was sent, by the earth's reference frame.
 By his frame, the moon's reception of the signal is after the earth's
 transmission, with the signal transferred FTL. But by the earth's frame,
 the reception is at an earlier time than the transmission.
 
 An Earth-Moon based FTL system could then get it back to the Earth in
 less than 1.2 seconds, making it arrive before it was sent.
 
 Hal >>



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