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Ask Dr. SETI ®

Chapter 4: Psychology

Searching Beyond the Water-Hole

Dear Dr. SETI:
First I wish to offer my encouragement to all in the SETI league. In my opinion manned space travel is too inefficient a means to seek out and discover life in and beyond our solar system. Radio astronomy and SETI could accomplish this far sooner and far cheaper.

Isn't SETI in effect a form of "Electromagnetic Archeology"?? Shouldn't SETI be respected as such?

My real question (the nagging one) is this: If other life forms think like us and construct transmission equipment and "respect" the water hole frequencies, might we be listening in the wrong place?? Picture their equivalent of the SETI league patiently listening to 1420 MHz while their brothers and sisters are watching cartoons broadcasted at high power on other portions of their EM spectrum. Perhaps more attention should be taken to listen on appropriate portions of the spectrum where high power signals could escape an earthlike atmosphere.

J. L.

The Doctor Responds:
The archeology analogy has been used by Philip Morrison. It is certainly apt. But you raise a very good point. As you might imagine, JL, this question receives quite a bit of attention among SETIphiles. My personal take on it is that while there might indeed be a "right" frequency to listen on, we can only guess as to what it might be. Which means, due to our ignorance, there are no "wrong" frequencies! We encourage SETI League members to scan the Water Hole, yes, but also any other interesting frequencies which strike their fancy. That way, maybe someone will guess right.

By the way, the range of frequencies which we should scan is not limited merely by atmospheric absorption, but also by cosmic noise, synchrotron radiation, and interstellar dispersion. The Project Phoenix receivers employed by our friends at the SETI Institute, for example, scan the whole region from 1.2 to 3 GHz. The so-called Microwave Window, the most transparent part of the spectrum, extends all the way from 1 to perhaps 10 GHz. And outside of the Earth's atmosphere, signals up to perhaps 100 GHz are viable. So you can see that there is plenty of spectrum to choose from. May your guess bear fruit!

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