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The Search for Signals From Space January 14, 2014

Posted by sandyclaus in Drake Revisited.


The Search for Signals From Space

JANUARY 11, 2014 – 5:00 AM – 0 COMMENTS

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(AP Images)

Editor’s note: This article by Carl Sagan was originally published in the Sept. 19, 1993, issue of Parade.

As children, we fear the dark. Anything might be out there. The unknown troubles us. But, ironically, it is our fate to live in the dark. Head out from the Earth in any direction you choose, and—after an initial flash of blue and a longer wait while the Sun fades—you are surrounded by blackness, punctuated only here and there by the faint and distant stars.

Even after we are grown, the darkness retains its power to frighten us. And so there are those who say we should not inquire too closely into who else might be living in that darkness. Better not to know, they say.

There are 400 billion stars comprising the Milky Way Galaxy. Of this immense multitude, could it be that our humdrum Sun is the only one with an inhabited planet? Maybe. Maybe the origin of life or intelligence is exceedingly improbable. Maybe civilizations arise all the time but promptly wipe themselves out.

Or, here and there, peppered across space, orbiting other suns, maybe there are worlds something like our own on which other beings wonder about who else lives in the dark. Could the Milky Way be rippling with life and intelligence—worlds calling out to one another—while we on Earth are alive at the critical moment when we first decide to listen?

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.

The cover of the Sept. 19, 1993, issue of Parade.

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 20,000 centuries, but we’ve had radio only for about one century. If they’re 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. 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 across much of the Galaxy. They should be able to do much belter.

If they exist.

But our fear of the dark rebels. We conjure up objections:

“It’s too expensive.” But, in its fullest modem 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 in common.

The laws of Nature are the same everywhere, so science itself provides a language of communication even between very different kinds of beings—provided they both have science.

“It would be demoralizing to learn that our science is medieval.” But, by the standards of the next few centuries, at least some of our present science will be considered medieval, 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. A serious student is 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 student struggles a little, acquires the new knowledge and, following an ancient human tradition, continues to turn the pages.

“All through history, advanced civilizations ruin slightly more backward civilizations.” 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 Extra-Terrestrial Intelligence (SETI), and I want to describe how far we’ve come.

The first SETI program was carried out by Frank Drake at the National Radio Astronomy Observatory in Greenbank, W.Va., in 1960. He listened to two nearby Sunlike stars for two weeks at one particular frequency. (“Nearby” is a relative term: The nearest was l2 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 tell if, because of the Earth’s rotation, it moves with the sky. If it’s not repeatable, you’ve learned almost nothing from it—it might be terrestrial radio interference or a failure of your amplifier or detector … or an alien signal. Unrepeatable data are not worth much.

via The Search for Signals From Space.



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