Since travel to even the nearest star would take quite a while (let's see, that's 4 light years -- call it 24 trillion miles. It's mostly interstate highway, so we can count on 65 miles per hour. Think we should pack a lunch?)
Seriously, according to one estimate, a 40 year round-trip to the nearest sun-like stars, in Alpha centauri A, would require as much energy as Earthlings consume in 1,000 years. And even if you could afford that much fuel, you'd need an impressively large tank to store it.
Thus anybody who wants to find intelligent life in space is adopting what we might call the "walkman" solution.
The Parkes 210-foot diameter radio telescope in Australia looked for signs of intelligent life elsewhere in the universe. Courtesy of Project Phoenix, Mountain View, Ca. and Australia Telescope National Facility.
Right. They're switching on the radio and hoping to hear signals from another planet ("This is K-E-T calling with the news from over the rainbow."). Problem is, since nobody has a radio guide to ET's transmitter, scientists have no idea what channel -- what frequency -- to monitor.
In SETI (the Search for Extra-Terrestrial Intelligence), as in most things, ignorance is not enough to prevent action, and for the past 30 years or so, people have been listening for signals from the Great Beyond. But experts warn that the time for listening is running out, since a fast-growing number of radio signals is masking the faint signals that may be coming from space.
Two of today's most elaborate SETI programs use different approaches:
The claimed discoveries of planets within the past year "have given us a moral boost, but we have always thought that planets were going around most stars," Werthimer says. To date, however, SERENDIP has searched each star that has shown evidence of planets, and "not found any radio signals." They have yet to analyze any signals they've recorded from Lalande 21185.
Question: how do the SERENDIP searchers plow through 4 million channels per second without wearing out their ears? With a computer, they search for parts of the spectrum where the signal is abnormally strong. Then they search the signals one of eight suspicious patterns, including pulses, regular changes in intensity, or anything resembling radar, television, or AM/FM radio signals.
After sampling 150 trillion signals over 20 years, using various instruments and telescopes, "almost all" suspect signals have turned out to be man-made noise, Werthimer says.
What keeps the SETI projects (which are privately funded) alive in the face of this stream of negative results? Simply the conviction that life must exist on some of the countless planets that, well, must exist. (Remember that most scientists think stars form from a disk of dust and gas, and that the outer portions of that disk eventually coalesce into planets.)
But it's not just planets, but also life that may be more common than once thought, Werthimer says: "We have only one example of a planet with life, and on that planet, life formed very early in history. That means life is not very hard to do. And we've found all sorts of complex organic molecules in space."
Indeed, in June, researchers at the American Astronomical Society meeting in Madison, Wis., reported the presence of vinegar in space. If vinegar were combined with ammonia, which is widely available in space, you'd have a simple amino acid called glycine. Amino acids are the building blocks of proteins, essential components of life as we know it. (Gastronomers are ardently awaiting the discovery of olive oil, fixings for an interstellar salad.)
Certainly, skeptics could interpret these negative results as proof that life -- at least the kind of life that appreciates radio -- just is not very common. But Werthimer says the results are partly a function of how much sky there is to sample, partly a function of how many wavelengths could carry the signals, and partly just human inexperience: "I think we Earthlings are just beginning to learn the tricks of the trade."
As far as Werthimer is concerned, the best advice is also the oldest: "stay tuned."
Beam yourself over to our bibliography to take further readings on this situation.
So far, nobody has claimed to see evidence of an extraterrestrial civilization, although interesting signals are heard now and then. "We have not found ET," says project manager Dan Werthimer of the University of California, "but we still think the universe is probably teeming with life."
