Why you should care
Because aliens may have already been in touch, and we’re thinking about calling them back.
We’re scouring moons and Mars for signs of life, but perhaps we should try posting to the intergalactic equivalent of a billboard instead. Nearly 40 years after receiving the so-called “Wow!” signal, which many believe was broadcast by aliens, researchers are starting to wonder whether we should call back.
If volunteer astronomer Jerry Ehman had written what he was really thinking that day in 1977, “we’d be talking about the ‘Holy Shit!’ signal right now,” says H. Paul Shuch, an engineer, radio astronomer and executive director emeritus of the SETI League, a grassroots organisation open to anyone interested in finding extraterrestrial intelligence. But Ehman showed remarkable restraint, writing a simple “Wow!” instead as he named the sequence of letters and numbers that may represent humankind’s only credible evidence of alien communication. Originally picked up by the Big Ear Radio Observatory on August 15, 1977, it wasn’t noticed until a few days later, when Ehman discovered the signal among the previous days’ logs.
He was sitting in his kitchen when he spotted a pattern that a couple of physicists had theorized 18 years earlier would signify alien chatter, according to Michael Brooks, the author of 13 Things That Don’t Make Sense . The printout read 6EQUJ5, a human way of cataloging the 72-second burst of sound registering at a frequency of 1420 MHz. The significance? E.T. may have phoned our home long before Spielberg set otherworldly hearts aglow with his 1982 film.
The Big Ear observatory was a key element of Ohio State University’s SETI project, launched in 1961 to map radio signals — including comets, quasars and nebulae — from outside the galaxy. From 1973 to 1995 (it’s since been decommissioned), it searched the cosmos for extraterrestrial radio transmissions, or anything deemed to be of unnatural origin, by listening to the sky and taking samples every 12 seconds. Each sample was given a code, and the accumulated data was printed every few days and submitted for manual examination.
In 22 years’ worth of data, the Wow! signal appeared just that one time in the 1420 MHz wave band. Since radio waves in such a narrow band don’t occur in nature, the only way to replicate it is to build a transmitter, which means the signal was artificial in origin. Also, the wave band falls within the small range of frequencies with the least amount of cosmic background noise, so it would’ve been the perfect venue for an extraterrestrial shout-out through the vastness of space — unlikely to be drowned out by droning galaxies or beeping pulsars.
Would-be pranksters have been ruled out because the UN’s International Telecommunication Union (ITU) has forbidden Earth-bound transmitters from using the 1420 MHz frequency. Moreover, complex geometry enabled astronomers to calculate that the signal’s source was stationary, so it couldn’t have come from an airplane, and there were no asteroids, moons or planets in a position to reflect an illegal man-made signal back toward Earth. All possible terrestrial origins, therefore, have been ruled out.
If humankind was going to pick up a radio signal from another race, in other words, the Wow! signal is exactly what we’d expect to find. But what’s puzzling is that the transmission — which came from the direction of the Sagittarius constellation — hasn’t been repeated since. If aliens were really trying to get in touch, wouldn’t they try more than once? Experts aren’t dissuaded. “There’s all sorts of uncertainty in science,” says Ehman, who retired from listening to the skies a few years ago and now volunteers at his local church.
But SETI colleagues might be poised to eliminate some of the uncertainty, sparking a debate over whether the community should start sending out signals of its own and invite an alien response — a process known as Active SETI. Trouble is, it’s a bit like shouting into a jungle, SETI Institute (a private educational organization searching for alien life) senior astronomer and director Seth Shostak points out, because there’s no telling what will respond, or how. This year’s annual meeting of the American Association for the Advancement of Science discussed a bold new plan for transmitting such messages, and drew mixed reactions. Among the dissenters was the acclaimed physicist Stephen Hawking, who has warned that trying to make contact with aliens could invite disaster. Ehman thinks Hawking’s been watching too much science fiction. Assuming that aliens couldn’t travel faster than the speed of light, he says, it could take millions of years for an alien race to receive our signal and then travel to Earth.
While the ramifications of broadcasting to aliens may be up in the air, so to speak, Shuch and much of the scientific community believe the mystery surrounding the Wow! signal boils down to two possibilities: It was an actual alien communication, or Ehman stumbled across a previously undiscovered natural astrophysical phenomenon.
“Either one would be worthy of a Nobel Prize,” Shuch quips. “If only we knew which.”