It’s the stereotypical sci-fi movie scene: The nerdy astronomer is sitting in a poorly lit room, searching through data for some kind of evidence that we’re not alone in the universe. Suddenly, among all of the bleeps and blips and printouts, something strange catches his attention…something that looks like nothing he’s ever seen before.
THE “WOW!” SIGNAL
That scene played out in real life on the morning of August 19, 1977. Jerry Ehman, an astronomer working at the “Big Ear” radio telescope on the outskirts of Delaware, Ohio, was going over the results of the telescope’s most recent survey of the night sky. His computer had spewed out pages and pages of numbers representing everything the telescope had detected. As Ehman was scanning the records from the night of August 15, a series of six numbers and letters stopped him in his tracks: “6EQUJ5.” What did they mean? In the language of radio telescopes, they represented an unusually strong burst of radio waves that originated in the constellation Sagittarius. Unable to explain what might have caused the reading, Ehman simply circled that part of the computer printout. Next to it, he wrote: “Wow!”
It was only later, as astronomers began to eliminate all other possibilities, that many became convinced that the “Wow!” signal was something more than a flash in space. Perhaps much more.
The hunt for extraterrestrial life was already well under way before that night in 1977, and it’s still going strong today, led largely by a nonprofit organization called SETI (the Search for Extraterrestrial Intelligence). SETI’s mission is to sanely conduct the search for “little green men”—a pursuit that some detractors claim is insane. SETI’s astronomers are generally skeptical of UFO sightings; most think it’s improbable that aliens have already visited Earth. SETI maintains that the universe is a very big place, so if we’re going to find life on other worlds, we’ll probably have to use powerful radio telescopes that can detect signals from a faraway, inhabited planet.
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Here’s how the thinking goes: If you were a member of an alien race living on a planet across the galaxy, and you pointed a regular optical telescope at our solar system, it would look like any other medium-sized star. However, if you pointed a radio telescope in our direction, it would be immediately apparent that one of the planets had life on it. Why? Because our radio and television signals escape our atmosphere every day and fly off into space. Theoretically, aliens could be watching Desperate Housewives right now.
SETI has access to some of the most powerful radio telescopes in the world—and in 1977, the Big Ear was one of the biggest. But it was designed to be largely automated (astronomers have better things to do than listen to radio static all day), recording the results of its observations on rolls of printer paper. And what Big Ear detected that day was a very intense radio signal. It had no way of converting that signal into sound or images; the only information it had was that small group of numbers and letters.
Looking at Ehman’s printout above, the numbers represent the “brightness,” or strength, of a signal that the radio telescope picks up—with 1 standing for a “dim” signal and 9 standing for a very “bright” one. In the unlikely event that the signal detected is stronger than a 9, the printout uses letters, with “A” being brighter than 9 and “Z” being the brightest possible source the observatory could record. So a signal that went as high as “U” naturally caught Ehman’s attention. In the 35 years that the Big Ear was in operation, this was the only time it detected a radio signal that powerful.
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It wasn’t just the power of the signal that caught Ehman’s attention; it was the way it rose and fell over the three minutes it was detected. The Big Ear was a massive telescope and couldn’t turn the way a normal telescope could to follow the stars across the sky; it could only sit there as stars came and went past its field of vision. So, given the Earth’s rotational speed, it could observe any point in the sky for only a few minutes as that point passed overhead. Any signal it detected would be expected to show up faintly, rise to its highest point, and then fall back down again. This is precisely what the “Wow!” signal did: It rose from 6 to E to U and back down to 5 again in exactly three minutes. This was a strong, steady signal.
Because no known object in the night sky should be emitting a radio signal that strong, astronomers crunching the data came up with several perfectly normal (and a few abnormal) explanations:
• Terrestrial sources: It’s possible that an ordinary local signal, like a television or radio broadcast, somehow got detected by the sensitive antennas of the Big Ear. Scientists consider this explanation unlikely; it’s illegal to broadcast radio waves of the strength detected—and even if someone did break the law, the direction of the signal made it almost certain that the source was in space.
• “Extraterrestrial terrestrial” sources: Some piece of radio transmission from the Earth may have hit a reflective surface in space (a satellite, a piece of space junk, or a meteor) that bounced the signal back to the Big Ear. The odds of this happening are…well, astronomical, but some skeptics are more comfortable with this explanation than some of the alternatives.
• Scintillation: Light from space scintillates as it moves through our atmosphere. This is a fancy way of saying it gets brighter and dimmer. (It’s what makes stars appear to twinkle.) Radio waves do something similar, and the Big Ear telescope may have detected an unusually powerful scintillation of a weak radio source in space—a quasar, for instance.
• Defective antenna: It’s also possible that the Big Ear was just malfunctioning. Radio telescopes are large, complicated machines, and any number of things can go wrong. But the Big Ear’s performance on that night has been checked and rechecked, and no problem has ever been found.
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• Something new: Since no known object in the universe emits such strong radio waves, and no (legal) device on Earth is even capable of it, it’s possible that the signal came from some unknown object in deep space—perhaps some undiscovered kind of star…or something even stranger.
Obviously, the most exciting theory is that the “Wow!” signal is a bona fide message from another world. But this explanation has problems of its own—namely, why haven’t they called back? The region of the night sky that the signal came from has been surveyed more than 50 times since 1970, by telescopes many times more powerful than the Big Ear. To date, there has been only radio silence from that patch of Sagittarius.
But that silence has done nothing to stop the speculation. Perhaps, some astronomers theorize, the signal comes in pulses, once every few hours or so, and we’ve simply missed it. Or it may sweep across the sky like the beam from a lighthouse. Or maybe it was a one-time thing, a brief transmission, or one that we caught only the tail end of. The SETI scientists can’t state outright that the signal was created by intelligent beings on a distant planet. However, they do admit that most of the other possibilities have been all but ruled out. “Either the ‘Wow!’ signal was an intercepted transmission from another civilization, or it’s a previously undiscovered astrophysical phenomenon,” said Dr. Paul Shuch of SETI. “Either possibility is mind-boggling.”
The Big Ear radio telescope is no more—it was torn down in 1998 to make room for a golf course, and its astronomers have moved on to other projects. But the questions raised by the “Wow!” signal haven’t disappeared. Meanwhile, astronomers still sit in small rooms, poring over mountains of data, hoping to be the one who detects that tiny blip that will alter the course of human history.
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