Re: SETI: SAT Spread Spectrum indistinguishable from normal

carl feynman (
Mon, 27 Oct 1997 16:15:43 -0500

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
>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.