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Ask Dr. SETI ®

Chapter 3: Philosophy

Are We Calling Them?

Dear Dr. SETI:
I have just seen the movie Contact, and now have some interest in SETI. Reading about Project Argus, it seems earthlings are fine tuning their equipment for certain radio signals; are we sending out any of these perfect fine tuned signals ourselves? Is there something somewhere which is sending out bleeps in prime numbers in these settings which we hope another advanced civilization will be optimized to pick up?

"Let us hope that either nature, or other civilizations, will provide us with other interesting signals of like amplitude, and sufficiently narrow bandwidth." (from Project Argus and the Challenge of Real-Time All-Sky SETI). - Are we doing this for other civilizations ourselves?

Thank you, Jon (age 15)

The Doctor Responds:
Your question shows insight and maturity beyond your years, Jon; you are to be commended. The short answer is, only once, so far. For the long answer, see Transmitting From Earth. For the details of the one message we did transmit (which did involve prime numbers!) see The Arecibo Message. For the pertinent international protocols, follow this link. And see this guest editorial for another viewpoint on transmitting from earth.

Remember, though, that if you transmit, and wait for a response, you may have to wait a very long time (in fact, twice the distance between us and the responding civilization). One advantage of starting out receiving is that signals sent thousands of years ago may just now be reaching our planet.

You should also note that it's far cheaper to receive than it is to transmit. We are a young civilization just developing its technology. One would expect the more mature civilizations (of which we hope for an abundance) to shoulder the task of building the high-power beacons. Once we've received one, I imagine it will contain instructions for building not a transport machine, but rather our own beacon transmitter!

I am gratified by one incidental aspect of your question. In asking whether we are transmitting such signals for "another advanced civilization," you seem to take their existence as a given. In that respect, your generation is light-years ahead of mine. By your reasoning, contact would seem no longer a matter of if, but of when. Let us hope you are right.

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