Re: SETI: SAT Spread Spectrum indistinguishable from normal star? (was Re: Movie ;contact)

Michael Lorrey (
Mon, 27 Oct 1997 21:43:44 -0500

Michael Butler wrote:
> Ah, but if the signal is maximally compressed, the signal can't be
> self-clocking. To recover the signal at the other end, you'd have to have
> a perfect clock and/or never miss a bit. Nicht wahr?

Isn't this the same requirement for the previously proposed FTL
communication, that you'd need the key already on the other end to be
able to tell what the noise means in the first place?

Also: If the clock is being referenced to say, a pulsar that all can
observe, then such a compression scheme is possible for widespread use,
> Now, the redundancy could be *vanishingly small*, just as you can approach
> c; and I agree with the limiting case--I just don't think it's a robust
> architecture. So it's a question on both ends: just how godlike are these
> hypothetical beings, and what purpose would they have in implementing the
> limiting case?
> On Mon, 27 Oct 1997, carl feynman wrote:
> > At 11:37 PM 10/26/97 -0800, you wrote:
> > >> such a signal would look just like white light, or starlight, or any type
> > >> of source desired. It would not be decipherable or even detectably
> > >> artificial unless the transmitting folk wanted it to be. For that
> > >> matter, any number of "stars" we see could just as well be
> > transmissions.--
> > >Umm... I'm not absolutely sure this is true. Would it not show some
> > >statistical evidence of the multiplexing?
> >
> > A perfectly compressed signal is indistinguishable from noise. Any
> > deviation from noise would be an opportunity for further compression. The
> > thermodynamic and information-theoretic definitions of 'entropy' coincide
> > to the extent that black-body radiation and a signal that is maximally
> > compressed look exactly the same. Indeed, I think the term 'entropy' was
> > coined in the information-theoretic sense for exactly this reason.

> Sounds right.
> > --CarlF

			Michael Lorrey
------------------------------------------------------------	Inventor of the Lorrey Drive
MikeySoft: Graphic Design/Animation/Publishing/Engineering
How many fnords did you see before breakfast today?