by Ben Miller
Kardashev’s paper said little about what these civilizations would actually be like, but did give a nod to a contemporary paper by the British-born American physicist Freeman Dyson, who had proposed a kind of Type II civilization which has come to be called a Dyson sphere. The gist of Dyson’s 1960 paper is this: An advanced extraterrestrial civilization might completely surround its home star with a swarm of artificial structures, to make use of every scrap of light. These structures would effectively enclose the star, completely blocking out most forms of electromagnetic radiation.
Objects like the Kepler Space Telescope, which orbits the Sun, are, of course, the first bricks in a Dyson-sphere-like wall. But if an advanced civilization completely surrounded its home star with light-blocking satellites, how would it show up in our telescopes? Dyson’s answer was heat. Heat, of course, is just another part of the electromagnetic spectrum, known as the infrared. So in principle, these sorts of civilizations should show up in infrared space telescopes if they are sensitive enough. Look for a large object radiating a lot of heat but little visible light and you just might find ET.15
So while the Americans were searching nearby Sun-like stars for microwave radio signals near the hydrogen line, the Russians were scouring the skies looking for large objects radiating in the infrared. Of the two strategies, you’d have to say that the Russians seemed to have the edge. A Type II civilization might be difficult to spot with a ground-based infrared telescope, which was all that was available at the time, but what about a Type III civilization? Who could fail to spot something the size of a half-blotted-out galaxy, where the dark bits were radiating strongly in the infrared? The Americans, on the other hand, were searching for a needle in a haystack. And yet it was the Americans who found something first.
THAT’S, LIKE, WOW!
I hope that got your attention. Because if you think that SETI has so far drawn a complete blank, you need to know about the Wow! Signal. It’s a bittersweet story, because unfortunately it’s the alien version of a kiss on the cheek rather than a committed long-term relationship. But again, I urge you: What follows is not the dramatic story of a UFO “enthusiast,” but a measurement that a very real SETI scientist made with a very real scientific instrument.
That scientist was the astronomer Jerry Ehman, and the instrument was the Big Ear Radio Observatory, a now defunct radio telescope belonging to Ohio State University. In fact, it’s more than defunct; it’s an eighteen-hole golf course. The Big Ear was a Kraus-type radio telescope, meaning it wasn’t the dish type you may be more familiar with, but instead consisted of two huge rectangular reflectors at either end of an enormous aluminum sheet the size of three US football fields. One reflector was flat, the other curved, and they were set up so that incoming radio waves bounced off the flat reflector, on to the curved reflector, and then into a detector. In fact, it’s such an ingenious setup I think it’s worth drawing, so here it is:
The Big Ear started its working life in 1965, and for twelve years it provided the Earth’s most detailed mapping of cosmic radio sources, known as the Ohio Sky Survey. Jerry Ehman had been a big part of that project, joining in 1967 after completing a PhD in astronomy at the University of Michigan. Sadly, in 1972 the Sky Survey had its funding withdrawn and Jerry lost his job. Unable to secure another research post at Ohio State, he started teaching business classes at nearby Franklin University while continuing to work on the Big Ear as a volunteer.
Rather than see their state-of-the-art telescope go to waste, Jerry and others continued working on it pro bono, rebooting it as a SETI project. Together, they converted the Big Ear from what’s known as a wideband instrument to a narrowband one. Most natural radio sources are wideband, meaning that they give off electromagnetic waves with a wide band of frequencies, sometimes from high-frequency x-rays all the way out to low-frequency radio waves. A good example would be quasars. Narrowband sources—no prizes for this—are bunched into a narrow band of frequencies. They are nearly always artificial; the best example would be a radio station.
The flat reflector at the Big Ear would be set into position, then as the Earth rotated it would scan a strip of the entire sky. After twenty-four hours, the angle of the reflector would be minutely adjusted, and the next strip would be scanned. Jerry and his ex-colleagues set up the Big Ear’s computer so that it would sample the intensity of the signal arriving in each of its fifty channels, convert it to a number between 0 and 35, then print it out.16 Or, rather, a number between blank and Z, because space on the printout was limited and that way two-digit numbers could be printed as a single digit: 10 was A, 11 was B and so on.
On Friday, August 19, 1977, Jerry Ehman sat down at his kitchen table to go through the latest batch of printouts. There on the right-hand side of the printout were the coordinates of the patch of sky that the Big Ear had been looking at, together with the time it had made each observation. And down the left-hand side were the signal intensity readings: the usual motley crew of blanks, 1s and 2s as the telescope soaked up the silence of the spheres. But wait. There, in channel 2, was something extraordinary: 6EQUJ5. Ehman took his red pen and circled the six digits, then next to them scrawled a single word: “Wow!”
So what did those digits mean? To you or me they might make an excellent personalized license plate for the presenter of a popular game show,17 but to Jerry Ehman they described a signal of unusual intensity, some thirty times more intense than the cosmic background radiation, flashing through the detector. Let me convert it to asterisks for you, so you get a feel for it.
Usually, Jerry would see this:
*
*
**
*
But this time he saw this:
******
**************
**************************
******************************
*******************
*****
And just to remind you, this compares to a maximum possible intensity of Z, or
***********************************
After a bit of number-crunching, Jerry was able to determine that the rising-and-falling shape of the signal was due to the movement of the telescope rather than any change in the intensity of the broadcast, which had remained more or less constant. The detection had lasted only seventy-two seconds, but it was impossible to say with certainty whether the source had been broadcasting for days, months, or even years before that because, as luck would have it, this was the first time that the Big Ear had scanned that particular strip of sky looking for narrowband signals. It was also impossible to tell whether or not the signal was carrying information; it could have been AM, FM, a single frequency switching rapidly or slowly on and off, or not varying at all.18
The most logical explanation seemed to be that an earthbound artificial signal had been bounced back into the telescope somehow, yet all efforts to explain Wow! in this way foundered. There had been no planets in the right position to reflect Earth signals back into the telescope, nor had there been any large asteroids or satellites. Aircraft, spacecraft, and ground-based transmitters were also ruled out. There was no getting away from it: The detected signal was exactly what you would expect from a point source located in the furthermost stars. What’s more, it was confined to a very narrow band of frequencies near the hydrogen line, just as predicted by Cocconi and Morrison all those years before.
Working back from the position data on the printout, Jerry and his team were able to narrow down the source of the signal to two small patches of sky in the constellation of Sagittarius.19 As you may know, from our point of view here on Earth, Sagittarius hangs like a net curtain over the center of the Milky Way Galaxy, and behind it lies a clot of distant stars. The same strip of sky was scanned again the following night, but the Big Ear heard nothing. In fact, the team kept the Big Ear in the same position for the next sixty days and nights, but the signal never returned.
So was the Wow! Signal the first message received by mankind from an e
xtraterrestrial civilization? Possibly. For us to be certain, we’d have needed to be able to repeat the observation, but so far all attempts to pick up more signals from that particular corner of the constellation of Sagittarius have proved fruitless. But it’s interesting, eh? Suddenly, the idea that we might pick up a signal in the very near future doesn’t seem so crazy after all . . .
THE REAL JODIE FOSTER
Jill Tarter certainly doesn’t think so. Jill is the astronomer that Jodie Foster’s character in the movie Contact is based on.20 From 1995 to 2004 she ran Project Phoenix, a SETI search of our nearest Sun-like stars. As ever with SETI, Phoenix relied on private funding, and had no dedicated radio telescope. Instead, it hopped around the globe, from the Parkes Observatory in New South Wales,21 up to the National Radio Astronomy Observatory, Green Bank, West Virginia, and finally to the Arecibo Radio Telescope in Puerto Rico. Rather than scan the whole sky like Big Ear, Phoenix targeted 800 of our nearest Sun-like stars, listening in on billions of narrow channels across a wide range of radio frequencies.
Sadly, at the end of this impressive search the result was nil: not one solitary alien signal. Does this mean we are alone? Not at all. As Jill Tarter put it in a recent interview, “the haystack we are searching in is vast.” In fact, let’s put some numbers to this. Even if our galaxy contains 10,000 communicable civilizations among 200 billion stars, we’d need to search around ten million stars before we found anything. So far we have searched a paltry 10,000 stars, and we’ve only really searched for one kind of signal, the kind we would send if it was 1950 and all we had was radio telescopes. So the silence doesn’t mean there’s nothing out there, it just means we live in the sticks. Who knows? As far as the Intergalactic Federation is concerned, maybe we live in a conservation area.
Clearly there is more work to be done, and thanks to a generous donation from the co-founder of Microsoft, Paul Allen, since the late noughties SETI has had its own purpose-built radio telescope. The Allen Telescope Array at Hat Creek Radio Observatory in Northern California represents something of a departure from the norm. Instead of building one large dish, the feeds from a large number of smaller twenty-foot dishes are combined using sophisticated electronics to create a much more versatile instrument, able to survey a wide area of the sky at a wide range of radio frequencies with extremely high resolution. In its current incarnation, the ATA has forty-two dishes; later stages will see it grow to 350 dishes.
The ATA has three very exciting goals. Firstly, it is going to search the nearest million stars for artificial signals over a large chunk of the microwave window, from 1 to 10GHz. So if there are any alien civilizations broadcasting radio waves within 1,000 light-years of the Earth, we are going to find them. Secondly, it is going to do the same thing for all the exoplanets that the Kepler Space Telescope has discovered. And thirdly—get this—it is going to survey the forty billion stars of the inner Galactic Plane for strong artificial signals near the hydrogen line. I don’t know about you, but I think it’s time the UN got itself a protocol.
FOLLOW THE METHANE
Back at the UN, Mazlan Othman and I have finished our lunch. In fact, we’ve been talking so long that the waitresses are wondering whether to offer us another meal. We’ve somehow got on to the topic of what a highly evolved species might look like, and whether they would even be that interested in the physical universe at all.22 As Mazlan puts it, why go to the trouble of building a spaceship to visit new worlds when you can just build virtual ones? That’s one answer to the Fermi Paradox: The aliens aren’t here because they are playing nine-dimensional Tetris.
The dream of SETI is to receive an extraterrestrial message that we can understand and respond to. But would it ever really be possible to communicate with species much more evolved than our own? “You and I need this,” says Mazlan, knocking on the tabletop. “We rely on the physical world for our existence. When I no longer have need of the material world, what am I? Maybe the purest form that a being can take is energy.”
I start to worry that someone might overhear us and call security. Isn’t she worried that this kind of loose talk is somehow, you know, unprofessional? “I think it’s a missed opportunity when people don’t want to talk about aliens. I want to hear what people believe. If it engages people, draws them in, then what have you got to lose? Because then we can ask ourselves, ‘what’s true?’ And then the discussion becomes meaningful.”
So what will it take for one of the member states to bring the SETI debate to the UN? What are the hard facts that would close the case for communicable extraterrestrial civilizations? A signal, obviously, would be pretty conclusive. But what about other evidence, like the number of potential habitats? After all, the Kepler Space Telescope has shown us that there are at least as many planets in the Milky Way Galaxy as there are stars. What’s more, those planets aren’t just found orbiting Sun-like stars, they are everywhere: orbiting red dwarf stars, binary stars, pulsars, and even wandering rogue, answering to no one. With so many places that life could take hold, surely the case for other intelligent, technologically advanced civilizations is easily made? What do we need to do to get people’s attention?
“You need to find life. Bacterial life.” Does she mean on Mars? After all, NASA’s Curiosity rover has proved that Mars was once habitable. “Maybe. Though Mars is so close to Earth that life could easily have traveled between them.” She’s got a point. As we shall see in the next chapter, evidence is growing that Mars, not Earth, had the chemical catalysts necessary to kick-start life. Once microbial life got going on Mars, the theory goes, it was then carried to the Earth by a meteorite. If that does turn out to be the case—and that’s a very big if—Martian life will turn out to be a branch on the same family tree as Earth life, and we’ll all be back to the drawing board. So where else should we be looking?
“I find Titan exciting. There’s a methane ocean, with lots of carbon, and that’s what we’re made of. If we found bacterial life on Titan, we’d really be making the case that life is widespread.” Titan, you’ll remember, is the largest moon of Saturn, with sandy beaches lapped by methane oceans, and methane clouds scudding across a sky pumped full of nitrogen. Could it be that a completely independent type of microbial life has made its home there?
And if Titan fails us, there’s always the icy moons of Jupiter. Beneath a crust of ice, Europa has an ocean of liquid water, and an atmosphere rich in oxygen. What’s more, unlike Titan, which currently has no scheduled mission, Europa is going to get a flyby when the European Space Agency’s JUICE probe launches in 2022. Maybe there are microbes lurking deep down in Europa’s hydrothermal vents? Curiosity may have proved that Mars was once habitable, but Europa is habitable right now.
THE HITCHHIKER’S GUIDE TO VIENNA
The art of being a good visitor is knowing when to leave, and every fiber of my being tells me that time was several hours ago. Mazlan asks me what my other business is in Vienna that day, and I give her the honest answer: to buy an ice cream and wander around the Old City. How about her? It is then that my genial host confesses that today is her day off. I am truly impressed. There are few people who would willingly spend time with me when paid, let alone when they could be watching daytime television with their feet up. As she is leaving the office, she says, how about she points me in the right direction, as the Old City is on her way home?
What follows is a tram ride around old Vienna, taking in the Opera House, the Austrian Parliament, and the Natural History Museum, though not necessarily in that order. With my bearings well and truly set, we then wander through the cool green of the Volksgarten, alone but for four silent American tourists riding on Segways. The other side of the Volksgarten gives out on to the Heldenplatz, and there looming in front of us is what looks like four Buckingham Palaces tongue-and-grooved together.
This, I learn, is the Hofburg Palace, one-time strong-hold of the Habsburgs, and even today the official residence of the Austrian President. It is also home to the National
Library, which is what Mazlan wants to show me. We cross the Heldenplatz, past two fierce statues of military heroes on rearing horses.23 Usually it wouldn’t strike me as at all odd to celebrate war and learning in the same monument, but in my current mindset I can’t help but wonder how all this would come across to the crew of an alien star cruiser.
Mazlan leads me into the library, where we find a riot of marble pillars, detailed frescoes, and Ancient Greek statuary. And it’s then that I have that day’s second light bulb moment, only this time it’s of the slightly less embarrassing, insightful kind. And that insight is this: Culture is key. In the Drake Equation, it’s just another number, the length of time for which a civilization is detectable. But culture is more than just the glue that holds a civilization together. Once I can write something down in a book, I no longer have to remember it. Statues tell a story that survives long after the heroes they commemorate have passed on. Culture is our way of storing information outside ourselves; a leap from the physical to the virtual.
I look up at the vaulted ceiling of the Hofburg to find an enormous biblical fresco, and I remember something else Mazlan had said, back when we were discussing what highly evolved beings might be like: “Maybe God is the alien. He is in all of our minds. He is pure consciousness.”
CHAPTER FOUR
UNIVERSES
In which the author brushes up on his astrophysics, builds a pocket cosmos, and discovers that if the universe had been created almost any other way then none of us would be here to witness it.