Hi Jan,
At 2000 June 11 - Sunday 23:54, Jan Steinman <olympus@xxxxxxxxxxxxxxx>
spoke about *Re: [OM] SETI searchers sought...* saying
> >So, don't be disappointed, the project is going to take some time.
> >The universe
> >is a REAL BIG place.
>
> Well, I'm not really hopeful that anything will be found. Information
> theory says that an optimally encoded signal is indistinguishable
> from noise, unless you have the decoding key. We have been sending
> easily intercepted and understood un-encoded signals into space for
> some 100 years, but only for about 40 years at the frequencies at
> which SETI@Home is listening.
I think the assumption is being made that they will be trying to
signal us.
>
> We are already beginning to encode signals in both time and frequency
> in a way that would make them unintelligible to an alien running the
> SETI@Home software. Digital cell phones, and soon, digital TV are a
> few examples. Wireless datacom uses "spread spectrum" techniques that
> render a signal almost impossible to even detect without the same
> frequency-hopping algorithm.
True, spread spectrum would be pretty impossible to detect, let alone
decode.
>
> Take a digital image, for example: a pattern of "ones" and "zeros"
> that anyone can recognize as a signal. Now save it as a JPEG, or even
> an LZW TIFF. Clip a bit out of the middle -- think we're going to be
> lucky enough to intercept the few parts per million of un-encoded
> header information? This compressed segment is totally meaningless.
> Convert to analog and play through a speaker and it will sound like
> noise.
>
> Take digitized sound -- again, a nice pattern, recognizable as an
> intelligent (well, with the possible exception of Rap music or Nixon
> tapes :-) signal. Now encode it as an MPEG Level 3 file (.MP3 for
> those using systems that still don't know the difference between a
> name and a type) -- once again, noise, unless you have the decoding
> key.
But SETI is trying to find the file headers, the disk format, the
bits, not the content.
>
> I think we have perhaps 100 years maximum in which to "catch" a
> civilization -- after they have begun to use electromagnetic
> technology, but before they have moved past it. There may be plenty
> of civilizations out there, but how many of those will be precisely
> in the window in which they are using technology we currently
> understand and can intercept?
>
There's also the window between discovering nuclear weapons and
discovering world government...
Tom
------------
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