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

Michael Butler (
Mon, 27 Oct 1997 17:10:38 -0800 (PST)

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?

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