Aliens almost certainly do exist. So why haven’t we yet met E.T.? It turns out we’re only just developing instruments powerful enough to scan for them, and science sophisticated enough to know where to look. As a result, race is on to find the first intelligent aliens. But what would they look like, and how would they interact with us if we met? The answers may come to us sooner than we imagine, for one leading astronomer believes she may already have heard a hint of their first efforts to communicate.
What Was the “Wow!” Signal?
By Susan Nasr, HowStuffWorks.com
Of all the signals received in the search for intelligent extraterrestrials, the Wow! signal is one that many people remember. And Jerry Ehman was the man who wrote it. Ehman taught astronomy and electrical engineering at Ohio State University and worked on early projects for Big Ear, a radio telescope at the university. These telescopes collect radio waves from space. Because cosmic radio waves are weak, the telescope collecting dishes have to be large, more than three football fields long in Big Ear’s case.
Ohio State let Ehman go after cutting Big Ear’s funding. Undeterred, he came back to Big Ear as a volunteer. Two colleagues helped Ehman. Without John Kraus, who conceived of the telescope, Big Ear wouldn’t have been listening. Robert Dixon, Kraus’s former student, designed Big Ear’s search plan, choosing the radio wavelength to listen to, and he corrected the listening to account for our galaxy’s spin. Without Dixon’s correction, Big Ear would have listened to the wrong wavelength.
To a layperson, the telescope looked like a shiny parking lot, with a wall on either end. One wall faced the sky to collect radio waves. Those waves traversed the ground, which was covered with a sheet of aluminum to preserve the signals and block interference, to the other wall, a curved one that sent the waves to a receiver. In 1973, Big Ear began searching for radio signals from life outside of our solar system. To do this, the telescope rotated with the Earth, collecting radio waves in a cone-shaped beam.
Big Ear had been searching for four years when it detected the signal on the night of Aug. 15, 1977. At the time, the telescope was looking in the direction of the center of our Milky Way galaxy, outside of our solar system. The signal was strong. Over the one minute and 12 seconds the waves were in the telescope’s search beam, the signal ranged from 5 to 30 times stronger than the background radio noise before it disappeared. Days later, Jerry Ehman saw the printout from Big Ear’s computer. With no one around to tell, he circled the sequence and wrote “Wow!”
Maybe the signal came from an object in space. Plenty of natural objects, from stars to black holes, emit radio waves. But on Wow’s line of sight in the sky, there were no known astronomical sources of radio waves at all. Wow did hail from a spot near Sagittarius A, a huge source of radio waves at the center of our galaxy, but the signal’s line of sight in the sky traced to a different line of sight. Of all the sources known then, Wow didn’t seem to come from a natural object in space. The radio signal also was narrowband; it ranged over few frequencies, unlike most natural radio sources in space, whose emissions range over many, many frequencies.
Later, Kraus wondered whether the radio waves came from an Earthly instrument in space. A circling satellite or a probe on a programmed course through space could have sent the radio waves as it sent data back to Earth. But the facts didn’t add up. First, Kraus’s group checked their list for instruments in space at the time. Nope. They made calls to see if they missed something. No luck. Besides that, humans usually send instruments to investigate moons and planets in our solar system, and the signal came from a plane apart from that plane. And second, man-made transmissions weren’t allowed at the 21-centimeter radio wavelength to which Big Ear was listening.
Kraus’s group began considering other events. Maybe a radio wave sent from Earth hit space debris and was reflected, Jerry Ehman once thought, but later decided the pattern didn’t match. Or the Wow! signal could have come from extraterrestrials. No data allows us to rule this out.
The answer is we don’t know. In 100 more observations of Wow’s sector by Big Ear, and more by others with different telescopes, no signal like Wow came again. It’s a common difficulty in the search for intelligent extraterrestrials: signals that look promising but can’t be thoroughly studied because they don’t repeat. Using their optical telescope, Paul Horowitz and Carl Sagan found 37 such signals during a decade-long search ending in 1995. But the search continues.
Video (Playlist): http://www.youtube.com/user/Moesty19#g/c/4053C848DFFF3D13