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The WOW! Signal

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Jerry Ehman was wowed when, on August 15th 1977, he received a radio signal from space that bore expected hallmarks of potential non-terrestrial and non-solar system origin.

Amazed at how closely the signal matched the expected signature of an interstellar signal in the antenna used, Ehman circled the signal on the computer printout and wrote the comment "Wow!" on its side. This comment became the name of the signal.

Science has a kind of golden rule, a principle that helps researchers distinguish between possible explanations for a phenomenon. The principle is called Occam’s razor, and it says that, given a number of options, you should always go for the simplest, most straightforward one. If we apply Occam’s razor to the signal received by the Ohio State University’s Big Ear telescope in August 1977, we can conclude that it was a signal from an alien civilization. Why? Because it was exactly what we had been told to look for.

In September 1959, sandwiched between an article on the electronic prediction of swarming in bees and one on X-ray-induced metabolic changes in erythrocytes, the first scientific article on the likely characteristics of an alien communication was published in the journal Nature. The article was written by Giuseppe Cocconi and Philip Morrison, two physicists from Cornell University in New York. Cocconi had an unremarkable background, but Morrison’s was more interesting. He earned his PhD under J. Robert Oppenheimer and played a vital role in the Los Alamos Manhattan Project. He was part of the team that traveled to Tinian Island in the West Pacific to assemble the atomic bomb that destroyed Nagasaki. After surveying the destruction, Morrison became a tireless champion of nuclear nonproliferation. He also helped found SETI, the search for extraterrestrial intelligence.

Morrison and Cocconi’s paper in Nature suggested that anyone wanting to attract another intelligent civilization’s attention would use radio frequency radiation. It is relatively cheap and easy to produce, and it travels a long, long way with a small power input. When it came to selecting a transmission frequency, they would choose one that spoke of some universal number in the cosmos. Morrison and Cocconi’s best guess was that an alien civilization would use something associated with the most common element in the universe: hydrogen. Any beings capable of communication would already have worked out and noted that hydrogen emits radiation at 1420 Mhz; this would be a number that would have special resonance everywhere in the universe.

An alien signal, then, would come in at 1420 Mhz. And it would be, as far as possible, only at 1420 Mhz. Sending a signal that is a composite of lots of frequencies uses a lot of energy; anyone wanting to get maximum distance per kilowatt on their transmission will use a narrow frequency range a “narrowband” signal. As an added bonus, no natural phenomenon emits narrowband radio frequency radiation, so the signal would make any intelligent listener prick up their ears.

On August 15, 1977, an exact match for Morrison and Cocconi’s signal arrived in Delaware, Ohio.

In the movie Contact, Jodie Foster gets a signal from space, and all hell breaks loose. The U.S. National Security Agency tries to take over the project, the president is briefed, and his advisers descend on the scene in sleek black military helicopters. Nothing like that happened at the Big Ear. Around 11:16 p.m. Eastern Daylight Savings Time, the signal hit the first of the Big Ear’s two receivers. The telescope’s computer recorded the signal’s arrival, a rise and fall in electrical current induced in the receiver’s wire mesh by an electromagnetic wave, then carried on recording whatever else came in from the sky nothing but noise, as it turned out. Three minutes later, when the Earth had turned and brought the telescope’s second receiver around to stare at that same point in the heavens, the signal had gone.

A few hours later by coincidence, it should be emphatically noted Elvis Presley died. It was only three days later, while more than twenty thousand people filed past Elvis’s open casket in Graceland, that the technician arrived at the Big Ear to stop the computer, print out the data, and wipe the hard disk clean. He came every few days; it was 1977, and the hard disk could only hold one megabyte. Perpetual data storage would be an unconscionable luxury for this long-shot project. On his way back up to Columbus, the technician dropped off the printout at Jerry Ehman’s house.

Ehman, the man who spotted our best candidate for an extraterrestrial signal, is practically a legend. Other people would have spotted it too, he points out, with his typical modesty. But who else would have had the naive enthusiasm, the passion to write “Wow!” in the margin? Other people might have marked the printout with an asterisk or an arrow. Jerry Ehman wrote the exclamation that properly captures the profundity of the moment.

Much to his surprise, the name stuck, but he shouldn’t be surprised. Wow! is a good summation of the importance of detecting an alien signal. It may even be an understatement. Talk to almost any astronomer in private and he or she will tell you it’s the biggest thing there is. We are pouring huge amounts of energy into the biological effort to understand where life came from, how it arose on planet Earth, because it matters to us; it is, perhaps, our deepest question. Really, it boils down to this: Are we special? The best summation has been attributed to the science fiction writer Arthur C. Clarke: “Sometimes I think we’re alone in the universe, and sometimes I think we’re not,” he said. “In either case the idea is quite staggering.”

Clarke is right. If we are alone, that’s extraordinary. If we are not, that’s even better. Were we to discover that we are one of many life-forms on a planet that is one of many inhabited worlds, we would have a new perspective on being human on being alive, even. And if we discover that some of that life beyond Earth is intelligent, a whole new vista of possible human experience opens up before us. We might, for the first time, have meaningful communication with another species.

That, really, is why we are looking for life beyond Earth or, more accurately, suitable conditions for life. As we have already seen, the Mars Rovers were looking not for life but for the signature that there is, or has been, liquid water on Mars. It’s not just Mars, though; the same search for the signs of water is going on with the Huygens probe on Titan, Saturn’s giant moon. Jupiter’s moon, Europa, has also had its conditions analyzed and been declared a potential haven for life. And these planets and moons within our solar system are just the beginning; the possibilities for life range across a whole universe full of planets.

We are living at a time of extraordinary progress in finding extrasolar planets; we did not spot the first one until 1988, but by August 2007 there were 249 confirmed sightings. There are several ways to do it. One is to identify anomalies in a star’s orbit, due to a planet’s mass pulling on the star. Or you can look at the starlight and see if it has become polarized if the orientation of its magnetic and electric fields has shifted by passing through a gaseous planetary atmosphere. Perhaps you’ll see a “lensing” effect where the planet’s gravitational field warps space around it and thus alters the path of the star’s light. Then there’s the “transit” method, where a star dims ever so slightly because a planet has passed across its face.

These are only a few of the techniques; there are plenty more, and they are all bearing fruit. In fact, it has got to the point where, if you want to make the news, just discovering an extrasolar planet is not enough. These days, to grab the front page you have to find a planet in its star’s Goldilocks zone.

As with the idea of a Goldilocks universe, the name comes from the conditions: in the Goldilocks zone, the temperature is neither too hot nor too cold, but just right for the stable existence of liquid water on the planet’s surface. So far, we have only found a few planets that orbit within the Goldilocks zones of their stars. In May 2006, for example, scientists announced they had discovered three planets, each with a mass equivalent to Neptune’s, orbiting a star about forty-one light-years away. The outermost of these was in the Goldilocks zone. The following April, researchers announced the discovery of Gliese 581c, a planet orbiting a star in the constellation Libra. It too lay in its star’s Goldilocks zone.

Though we are making great progress with finding suitable extrasolar planets, when it comes to detecting alien life there’s a problem: the planets are so far away. There is a chance we might see signatures of possible life, or at least suitable conditions for life, in the spectrum of radiation from their surfaces or atmospheres, but we have little more to go on. If there are dormant life-forms on their surface, we won’t ever know for sure. Without some dramatic leap in our technological abilities, there is no way for us to send probes or people to extrasolar planets. What we really need, then, is for that life to get in touch with us. It has never happened, or at least not in a way that convinces everyone who looks at the evidence. But the Wow! Signal remains our most tantalizing indeed our only possibility.

Jerry Ehman was in his kitchen when he read the printout from Big Ear. He was sitting at the table, with three days of data in front of him. On the printout, the signal came in as “6EQUJ5.” The letters and numbers are, essentially, a measure of the intensity of the electromagnetic signal as it hit the receiver. Low power was recorded with numbers 0 to 9; as power got higher, the computer used letters: 10 was A, 11 was B, and so on. 6EQUJ5 was the signature of a signal that steadily grows in intensity, reaches a peak, then falls away again. The U was the highest power signal the telescope had ever seen. The signal’s spread was astonishing too: less than 10kHz. That’s somewhere around a millionth of the transmission frequency. By anyone’s definition, it was a narrowband signal at 1420 Mhz. Ehman knew what Morrison and Cocconi had said about the likely shape of alien signals. This fit exactly.

6EQUJ5 came up early in the printout Ehman marked it with that Wow! and went through the rest of the printout to see if it happened again. It didn’t. It was enough, though. Eighteen years before the Wow! Signal hit Earth, before SETI had even been conceived, two physicists had predicted what an alien communication would most probably look like, and their prediction looked uncannily like the signal Ehman saw. If you believe that science should progress through theoretical predictions that are followed up by confirming observations, the alien hypothesis is a slam dunk.

So where has ET been hiding? The signal came from a single point in the heavens. Immediately on recognizing the signal, Ehman and his boss, Robert Dixon, consulted their star maps to see what astronomical body might be emitting it. The signal came from the constellation of Sagittarius, also known as the Teapot. Just to the northwest of the globular cluster M55 (to the east of the Teapot’s handle) to be exact. There was nothing there.

Although the signal’s shape didn’t look at all like it had been created by accident, the researchers also looked for satellites or spacecraft or even aircraft that might have emitted a signal or interfered with terrestrial signals, creating something that looked like the Wow! Signal. Not only were there no man-made objects that could do it, the signal was of a frequency that global governments agreed was banned from use. There was no good explanation.

Three decades later, there still isn’t. And there’s very little more that one can say. The Big Ear researchers never saw anything like the Wow! Signal again. They looked for it more than one hundred times. Nothing. All the subsequent printouts were bland numbers, signifying the stubborn absence of anything interesting coming to us from the deep reaches of the cosmos. Most of our searches for alien intelligence have been similarly long, dark, eventless efforts. Occasionally something interesting has spewed out of the telescopes, but it has always turned out to be a spurious reflection off a satellite or a spacecraft, or interference from some piece of cosmic rock.

Though many have tried, no one has ever come up with such an explanation for the Wow! Signal. The researchers at Big Ear have analyzed a wide variety of possibilities: satellite transmissions, the harmonic frequencies of ground-based radio transmitters reflected off space debris, aircraft signals, terrestrial TV or radio signals, and anything else they could think of. Nothing could explain the characteristics of the observed signal. The first time I had contact with Ehman, he told me he was “still waiting for a definitive explanation that makes sense.” Not that he believes it was aliens; he doesn’t like to “believe” anything. It’s just that it’s the only satisfying explanation if a one-off contact with ET can be classed as something satisfying.

In fact, it’s this, the singular nature of the signal, that is its Achilles’ heel. In Contact, Jodie Foster recorded hours, days, even weeks of extraterrestrial messages. The Big Ear received just one. Even the second receiver that looked at the same spot in the sky three minutes later saw nothing. That certainly makes it tempting to dismiss the signal. It must have been some flutter in the electronics, or a bubble exploding in the telescope’s nitrogen cooling system, or ...something. If it was ET, then he, she, or it didn’t broadcast for long surely any deliberately broadcast signal would last for longer than three minutes?

The problem with that theory is that there’s no reason for the assumption. Worse, everybody searching for extraterrestrial intelligence knows that intelligent beings could quite feasibly send one signal out into space followed by absolutely nothing else. They know that because we have done it ourselves.

In 1974 NASA arranged for the Arecibo telescope to beam a message out toward M31, a star-studded galaxy that seemed a good candidate for our nearest extraterrestrial homestead. The message was a stream of binary digits that, if you put them together right (carefully placed prime numbers provided clues), showed a crappy Atari Pong-style picture of a person, a DNA double helix, and our solar system. Anyone in M31 who picks it up which won’t happen for about twenty-one thousand years may well conclude there is intelligent life out here. They may even be able to pinpoint where it came from. For that civilization on M31 it is likely to be a momentous event their first contact with intelligent aliens. However, if they are anything like us, M31’s brightest skeptics will smugly point out that you can’t draw definitive conclusions from just one signal, no matter how well crafted. As any intelligent civilization knows, a sample of one is useless, statistically speaking. If ET really wanted to get in touch, there’d be two signals, at least. Wouldn’t there? What a thought: we might have messed up our first communication with our cosmic neighbors. So perhaps we can take comfort in the fact that they seem to have made the same mistake.

If there is no way to make the Wow! Signal make sense, there is also no way to invoke the other golden rule of science: repeat the observation. Today, there is no publicly funded search for alien intelligence and there is no Big Ear. In 1988 the telescope was dismantled to make way for a luxury golf course. John Kraus, Big Ear’s designer, learned Ohio Wesleyan University had sold the ground out from beneath his beloved telescope on December 28, 1982. He called it a day of infamy. “Ohio Wesleyan betrayed my trust and sold the land out from under the ‘Big Ear,’ ” he wrote in April 2004. “What other discoveries and measurements might have been made if the telescope had not been demolished?” The fact is, there had been nothing more than a gen-tleman’s agreement between Ohio Wesleyan University and Ohio State University, whose faculty had built the telescope. The local papers raised an uproar, and the OWU president resigned shortly afterward. The astronomers got together and offered the developers four times the land’s value. The protests and the efforts, ultimately, made no difference.

Money, greed, and ambition have continually thwarted the search for extraterrestrial intelligence. Somehow, it seems more open to attack than any other branch of science. Perhaps because, as such a long shot, it is so vulnerable to cheap shots.

The first really cheap shot against SETI was fired just six months after the Wow! Signal hit Earth. Senator William Proxmire was looking for another recipient for his infamous Golden Fleece Awards. He handed them out to government-funded projects that he considered a waste of taxpayers’ money. It was a great PR campaign for Proxmire, giving the voters exactly what they were looking for at the end of a difficult decade, but it wasn’t always easy to keep coming up with targets especially when he had committed himself to issuing one a month.

NASA’s turn came around in February 1978 “for proposing to spend $14 to $25 million over the next seven years to try to find intelligent life in outer space.” Scientifically, there was never anything wrong with the idea. The badly titled (by today’s snazzy science-PR standards) “Microwave Observing Program” (MOP) had the support of mainstream scientists, and it had a moderate annual budget of around $1.5 million; it was a sensible effort to use microwave receivers to look for anomalous signals from outer space. Nevertheless, Proxmire’s attention made it vulnerable, and, in 1982, he went in for the kill, tabling a legislative amendment that cut all federal funding for MOP. Fortunately, Carl Sagan came to the rescue.

Sagan’s influence can be measured in TV viewing figures. His series Cosmos, produced in 1979, was the most-watched public program in America until the 1990s. Around 600 million people have seen the series and gained Sagan’s charismatic, inspiring, and breathtaking perspective on the universe. When, in 1982, Sagan met with Proxmire, he was at the height of his influence. Proxmire listened to Sagan’s arguments in favor of SETI and backed down he even apologized. Sagan followed up with a PR campaign of his own, backed up by a petition signed by some of the world’s most respected scientists (with seven Nobel laureates among them), and cemented the search for extraterrestrial intelligence in the American mind as a worth-while even a necessary scientific endeavor. No wonder, then, that Nevada senator Richard Bryan refused to meet with SETI astronomers when he launched his attack on the program a decade later.

On October 6, 1992, the New York Times was enthralled by the prospect of a new extraterrestrial frontier for America.

ASTRONOMERS, moving beyond philosophical musings and science-fiction fantasy, are about to mount the first comprehensive, high-technology search for evidence of intelligent life elsewhere in the universe. The new search is scheduled to begin symbolically on Monday, the 500th anniversary of the day Columbus happened on the shores of America.

Almost exactly a year later, the same paper expressed a numb shock under the headline “ET, Don’t Call Us, We’ll Call You. Someday.” LAST year, on the 500th anniversary of Columbus’s arrival, NASA announced a 10-year project to scan the skies for radio waves emitted by alien civilizations. As Columbus Day 1993 comes around, the program is being canceled, the $1 million a month needed to sustain it eliminated from the budget. The writer George Johnson could not resist stretching the analogy. It was as though the Great Navigator, having barely sailed beyond the Canary Islands, was yanked home by Queen Isabella, who decided that, on second thought, she’d rather keep her jewels.

This disaster for SETI was due to Bryan. He had tabled a late-night amendment to a bill that killed the funding. In support of his amendment, Bryan made the facile comment that “millions have been spent and we have yet to bag a single little green fellow. Not a single Martian has said take me to your leader, and not a single flying saucer has applied for FAA approval.”

This time SETI’s champions could do nothing. Seth Shostak, now director of the SETI Institute, the privately funded successor to NASA’s SETI, recalls that they requested meetings with Senator Bryan, but Bryan wouldn’t take them. Bryan’s amendment went through, and the publicly funded effort to answer the biggest question on Earth was over. It never recovered; the New York Times registered its amazement at the shortsightedness of the move, but nothing changed. Public funding of SETI was finished. At present, the money pot for SETI is provided almost exclusively by Silicon

Valley entrepreneurs. When SETI lost its funding in 1993, Barney Oliver, the head of Hewlett-Packard’s research and development division and the man who gave the world the pocket calculator, made some calls. Oliver’s true love was not technology but astronomy and, in particular, SETI, and he got Bill Hewlett and David Packard to make a contribution to keep SETI’s head above water.

It is entrepreneurs like Hewlett and Packard who, for reasons no one quite understands, have kept SETI alive to this day; their contributions have allowed SETI people to buy a little telescope time and to pay a few salaries. But Hewlett and Packard are now dead, and it is another of Oliver’s contacts, Microsoft cofounder Paul Allen, who is the main source of funding. Nevertheless, the construction of the SETI Institute’s very own telescope the Allen Telescope Array is stalling because Allen feels his contribution should be matched by public funds, and no one with control over a public purse is willing to give any money for the construction.

It’s easy to see why people who are accountable for public money might shy away from funding a search for extraterrestrial intelligence. Jerry Ehman admits it’s like looking for a needle in a haystack “except that you don’t know where the haystack is, and you don’t even know for sure there’s a needle in it.” It’s true that the search for intelligent aliens relies on a barrage of assumptions, and one has to hope that some of them are not too wrong. But the same could be said of the search for extrasolar planets a venture that has no trouble getting public money.

Take the current vogue for finding planets within the Goldilocks zone. When we stop and think about our limited appreciation of what life might be like, and what conditions it can thrive under, that whole set of criteria based on the existence of liquid water stars to look pretty shaky. Liquid water is not a necessary requirement for life to exist and flourish; in some circumstances it can be the kiss of death. Sulphuric acid might do the job for other forms of biology, for example; the atmosphere of Venus is rather like a cloud of battery acid, and scientists have speculated that its acid droplets could harbor life. That’s precisely because there is no water around. It is water that makes sulphuric acid corrosive; in fact, the acid is a catalyst for the corrosion reaction, known as hydrolysis, where water splits protein molecules.

Similarly, engineers have found that some biological enzymes used in industrial chemistry work in the hydrocarbon fluid hexane as well as in water. There is even a chance that biology can work without carbon; its near-relation silicon can also act as the scaffold on which biological molecules are built. On Earth, water and carbon are abundant, and silicon is locked up in the planet’s rocky crust sand, for instance, is mostly silicon. It’s no surprise, then, that terrestrial life is carbon- and water-based. On other worlds, however, the kinds of distant worlds we are straining to see, there might be a sandman staring back at us. And those silicon-based eyes might well have developed far from the Goldilocks zone.

If the development of sand- or sulphuric acid–based life broadens the criteria for the search for other habitats, it also makes SETI’s job much harder; the communication is even more likely to be something we haven’t considered possible. But just as it hasn’t stopped the search for life-harboring extrasolar planets, neither does it render SETI pointless.

There have been attempts to do that. Perhaps most famous is the remark that the Italian physicist Enrico Fermi made in 1950: “Where is everybody?” Fermi’s point was that, for all the vast reaches of space and the almost limitless possibilities for intelligent life to develop in the universe, we have not encountered any aliens or alien communications. Many answers have been raised to the Fermi Paradox, including suggestions that aliens might not want to visit or communicate with us, or that they are already living among us, but the most compelling explanations are that we are not really looking or listening, and if we were, we wouldn’t necessarily know what to look or listen for.

It is certainly true that we don’t know what a deliberate signal would look like. Morrison and Cocconi’s idea seems to hold water but could be rather primitive. If an alien civilization is advanced enough to be beaming speculative signals into space on a regular basis, it’s likely to be far more advanced than we are. To them, our ideas of what makes a good signal may be the equivalent of smoke signals or semaphore: hopelessly outmoded and inadequate.

Our best hope would be that the aliens communicate using a mathematical code a string of prime numbers or the digits of pi, or some other cipher we believe to be a universal experience. But there are other options. A project at Harvard University uses spectra gathered from optical telescopes to search for signatures of “always on” laser light beamed from deep space. A Berkeley project is looking at 2,500 nearby stars for pulses of laser light that might have been emitted by a distant civilization. Most SETI projects, including the Allen Telescope Array when it is up and running, look for Morrison and Cocconi’s narrowband radio signal; although it would bear no information (at least none that we could detect using the current generation of instruments), the repeated observation of such a signal might release enough funds for us to build radio telescopes that could decipher any signal contained within it. Or that’s what the SETI Institute is hoping. WHERE does all this leave the Wow! Signal? Inconclusive.

The fact that it came from an empty region of space, not somewhere known to be a candidate for the development of alien life, means the best we can suggest is that it was a signal from an alien spacecraft, perhaps an identifier beacon aimed momentarily and erroneously in our direction as a civilization migrated through the cosmos. But here we stray into the realm of science fiction. Interestingly, the SETI Institute Web site’s take on the Wow! Signal invokes another anomaly. “You wouldn’t believe cold fusion unless researchers other than the discoverers could duplicate it in their labs. The same is true of extraterrestrial signals: they are credible only when they can be found more than once.” Don’t take it at face value, it suggests, but do look for more examples.

Are we looking? Not really. The search for aliens is for enthusiasts only. Considering what scientists say is at stake, this ought to be a scandal. The Wow! Signal, if it is what it seems, is a classic Kuhnian anomaly: follow it up, and we could radically alter our understanding of the cosmos and our place in it.

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