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From: ech@spuxll.UUCP (Ned Horvath)
Newsgroups: net.physics,net.astro
Subject: Re: RE: FLASHING QUASARS
Message-ID: <492@spuxll.UUCP>
Date: Sat, 9-Jun-84 01:24:49 EDT
Article-I.D.: spuxll.492
Posted: Sat Jun  9 01:24:49 1984
Date-Received: Sun, 10-Jun-84 00:32:27 EDT
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Question: could one build a bigger-than-one-light-second object that "flashed"
with a period less than a second?  As viewed from SOMEWHERE?

Sure; to take a trivial example, place yourself at the center of an
arbitrarily large shell, and make a BIG flash at an arbitrary frequency.
The reflections off the shell will appear to come from all directions
simultaneously.

The upper bound on size based on frequency is based on the assumption
that one is NOT at any such privileged position with respect to the periodic
system; given that there is a large number of (pulsars, quasars, you name it)
that exhibit the periodic behavior, the suggestion that one is at some
privileged position for ALL of them is absurd.

So, throw that out.  Contrived examples, at least as gedanken experiments,
can always be had.  The argument goes

	1. We assume that we are viewing a single periodic system in each
	   case, and
	2. In order for a physical system to display any sort of behavior
	   the various "parts" must be able to interract, and
	3. No interraction can propagate at more than the speed of light.

You don't have to accept ANY of these assumptions; the contrived example
with the shell, for example, violates assumption 2, i.e. that the
various parts of the shell are interracting.  If you are willing to accept
the first two assumptions as reasonable, and the speed of light
limit (an axiom of relativity, by the way, not a theorem!), then the
argument yields a (very crude) upper bound on the size of the system.

Does that help?

=Ned=