What's all this about SETI?

Many of the creationists on this forum keep bringing up the search for
extra-terrestrial intelligence (SETI) as an example of a method for
detecting Intelligent Design. Dembksi's articles repeatedly refer to
SETI. For examples see:
http://www.firstthings.com/ftissues/ft9810/dembski.html
http://www.arn.org/docs/dembski/wd_isidtestable.htm
http://www.arn.org/docs/dembski/wd_idtheory.htm

Dembski admits that his example of SETI is not based on what SETI
researchers are actually looking for, but a fictional scenario in Carl
Sagan's novel _Contact_, where a binary signal
110111011111011111110... is received. In this signal, each run of 1's
has a length given by the next larger prime number (2, 3, 5, 7...)

SETI is actually doing something much more simple. All SETI is looking
for is a beacon; that is, a simple high-power transmission at a fixed
frequency. A simple beacon would be pretty strong evidence of an
extra-terrestrial intelligence (ETI), and there is no need to resort
to Dembski's Complex Specified Information (CSI).

SETI does not need a complex signal, a mathematical sequence, or a
binary communications channel to imply an ETI. It is only looking for
a strong simple tone, which would indicate the existence of a powerful
extraterrestrial amplifier. Data on a carrier is not needed. The
carrier itself suffices.

SETI assumes that an ETI would use the quietest band of cosmic
background radiation (0.5-60 GHz) in order to maximize the
signal-to-noise ratio of its beacon. Because of the properties of
Earth's atmosphere (of which the ETI is presumed ignorant), our best
reception is in the 1-12GHz band and that is our best place to look as
long as our receiver is terrestrial.

The [EMAIL PROTECTED] project, for example, scans a 2.5MHz band centered at
the 1.42GHz (21 cm) hydrogen line. It assumes a beacon transmitting at
the hydrogen spectral line. The 2.5MHz bandwidth allows for Doppler
shift resulting from the relative motion of transmitter and receiver
(on rotating, orbiting planets), up to 270 kilometers per second.
[EMAIL PROTECTED] actually looks for the Doppler shift that would indicate an
extraterrestrial, fixed-frequency beacon.

The hydrogen line was chosen for two reasons: first, due to the
prevalence of hydrogen in the universe, it might be a logical
reference frequency (though there are many other possible reference
frequencies). Second, terrestrial emissions near spectral lines are
protected for radio astronomy by the International Telecommunications
Union (ITU) and national communciations authorities, improving the
chance that a signal received is not of terrestrial origin.

http://skyandtelescope.com/resources/seti/article_248_1.asp
http://www.planetary.org/html/UPDATES/seti/HIW5.htm
http://dsnra.jpl.nasa.gov/freq_man/ra_freqs.html

There is another reason, however, that Dembski's favorite prime number
sequence is a poor choice of signal, having to do with optimum use of
a channel. To minimize the error rate in a binary symmetric
communications channel, it is necessary that the probability of
transmitting a 1 and the probability of transmitting a 0 be roughly
equal. The prime number sequence described by Dembski results in an
unbalanced transmission of nearly all 1's, which would cause an
unacceptably high error rate. It is highly doubtful that an ETI would
choose to transmit a special mathematical message for which the error
rate is high.

In short, creationists' continual attempts to link SETI with
Complexity and Intelligent Design are nonsense resulting from the
ignorant use of science fiction.