Pale Blue Dot - Carl Sagan [126]
Our species has discovered a way to communicate through the dark, to transcend immense distances. No means of communication is faster or cheaper or reaches out farther. It’s called radio.
After billions of years of biological evolution—on their planet and ours—an alien civilization cannot be in technological lockstep with us. There have been humans for more than twenty thousand centuries, but we’ve had radio only for about one century. If alien civilizations are behind us, they’re likely to be too far behind to have radio. And if they’re ahead of us, they’re likely to be far ahead of us. Think of the technical advances on our world over just the last few centuries. What is for us technologically difficult or impossible, what might seem to us like magic, might for them be trivially easy. They might use other, very advanced means to communicate with their peers, but they would know about radio as an approach to newly emerging civilizations. Even with no more than our level of technology at the transmitting and receiving ends, we could communicate today across much of the Galaxy. They should be able to do much better.
If they exist.
But our fear of the dark rebels. The idea of alien beings troubles us. We conjure up objections:
“It’s too expensive.” But, in its fullest modern technological expression, it costs less than one attack helicopter a year.
“We’ll never understand what they’re saying.” But, because the message is transmitted by radio, we and they must have radio physics, radio astronomy, and radio technology in common. The laws of Nature are the same everywhere; so science itself provides a means and language of communication even between very different kinds of beings—provided they both have science. Figuring out the message, if we’re fortunate enough to receive one, may be much easier than acquiring it.
“It would be demoralizing to learn that our science is primitive.” But by the standards of the next few centuries, at least some of our present science will be considered primitive, extraterrestrials or no extraterrestrials. (So will some of our present politics, ethics, economics, and religion.) To go beyond present science is one of the chief goals of science. Serious students are not commonly plunged into fits of despair on turning the pages of a textbook and discovering that some further topic is known to the author but not yet to the student. Usually the students struggle a little, acquire the new knowledge, and, following an ancient human tradition, continue to turn the pages.
“All through history advanced civilizations have ruined civilizations just slightly more backward.” Certainly. But malevolent aliens, should they exist, will not discover our existence from the fact that we listen. The search programs only receive; they do not send.*
THE DEBATE IS, for the moment, moot. We are now, on an unprecedented scale, listening for radio signals from possible other civilizations in the depths of space. Alive today is the first generation of scientists to interrogate the darkness. Conceivably it might also be the last generation before contact is made—and this the last moment before we discover that someone in the darkness is calling out to us.
This quest is called the Search for Extraterrestrial Intelligence (SETI). Let me describe how far we’ve come.
The first SETI program was carried out by Frank Drake at the National Radio Astronomy Observatory in Greenbank, West Virginia, in 1960. He listened to two nearby Sun-like stars for two weeks at one particular frequency. (“Nearby” is a relative term: The nearest was 12 light-years—70 trillion miles—away.)
Almost at the moment Drake pointed the radio telescope and turned the system on, he picked up a very strong signal. Was it a message from alien beings? Then it went away. If the signal disappears, you can’t scrutinize it. You can’t see if, because of the Earth’s rotation, it moves with the