Re: [asa] Contact with Alien Civilizations

From: Iain Strachan <igd.strachan@gmail.com>
Date: Mon Jun 18 2007 - 17:49:17 EDT

On 6/18/07, David Campbell <pleuronaia@gmail.com> wrote:
>
> > The Carl Sagan (first contact) idea (often cited by Dembski) is a
> sequence
> > of prime numbers. That's not THAT intelligent, of course, but it would
> be
> > world headline news if such a signal were received from outer space.
>
> This also illustrates a major difficulty of SETI. Most of our signals
> are too complex for easy detection of pattern.

I don't think that's necessarily true. Non-noise exhibits a complex
probability distribution, where as true noise exhibits a simple probability
distribution. There is a well-known statistical technique called
Independent Components Analysis that can separate out statistically
independent components from a mixture of signals, by looking at deviations
from Gaussian noise (non-Gaussianity). This technique is very good at
"Blind source separation", for example separating out the individual
speakers from the mixture of voices at a coctail party (aka "The Cocktail
Party Problem"). One might envisage techniques such as this to separate out
independent channels from, for example a mixture of radio signals.

Unless they are
> deliberately sending a simple message so as to be readily detected,
> it's unlikely to be detectable as non-noise.

This is the general idea - a deliberate "hello" to anyone out there.

I think the Sagan thesis goes along the following lines. Any alien
mathematics. And they would reason that any civilisation advanced enough to
receive radio signals must also have discovered mathematics. So if you want
to communicate your presence, you would use the "universal language" of
mathematics.

Human scientists adopted this line of thought in the "Arecebo signal" sent
towards the globular cluster M13 in 1974.
http://en.wikipedia.org/wiki/Arecibo_message . The "image" consisted of
1679 pulses. This was chosen because 1679 is the product of two primes
(23x73) and so there would be only two ways of arranging the pulse sequence
into a 2-D image. The image depicted the first ten numbers, the atomic
numbers of the elements that make up DNA, a depiction of a stick-like
person, and various other astronomical images (all in a 23x73 pixel image!)

Iain

(Of course, probably the
> vast majority of electronic signaling on earth shows little sign of
> intelligence even when processed with knowledge of the transmission
> method). It's far from evident that an intelligent designer of the
> sort envisioned by ID should be expected to encode something
> analytically similar to a sequence of primes in DNA.
>
> --
> Dr. David Campbell
> 425 Scientific Collections
> University of Alabama
> "I think of my happy condition, surrounded by acres of clams"
>
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Received on Mon Jun 18 17:49:53 2007

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