The Search for Intelligent Light
Planet hunter Geoff Marcy scans the skies for answers to the universal question of other life.
Even the most casual driver need strap in to negotiate the perilous twists of the single-lane road that winds up California’s Mount Hamilton to the Lick Observatory. But the biggest twist of the evening will require something of a mental seat belt. It lies inside the control room of the three-meter telescope, where University of California, Berkeley astronomer Geoff Marcy and his colleague from San Francisco State, Debra Fischer, train their lens on distant stars and search for a telltale sign of advanced stellar civilization: lights.
Yup, these are reputable scientists looking for extraterrestrials — though not the little fingertip-lit variety that just want to phone home. Marcy and Fischer seek laser lines — that is, high-powered lasers used by advanced civilizations to communicate or, possibly, power their spacecraft.
While characterizing the search as an “extremely long shot” and “sounding bizarre,” Marcy is perfectly straightforward and not the least bit apologetic about this research.
“The project is a one-in-a million chance. But you have to do it, because if it’s there, you can’t be too arrogant not to look,” he said. “This is somewhere between harebrained and stupendous. But if we find intelligent life, it would supersede the discovery of fire.” Marcy has not requested funding for this work, which he does in his "spare time," because it has such a low probability of success.
He has a long and storied track record of not being “too arrogant not to look” for things that few believed possible. This began in 1983 with a search for planets — not the planets of our solar system but extrastellar planets (i.e., twin Earths). At the time, it was a part of science considered the “lunatic fringe.” No one had found any, and no one was trying because the technology to detect a planet simply hadn’t arrived.
Marcy was unfazed. Scientists have known since the early 1900s that a star orbited by a planet would move or “wobble” just a little because of the planet’s gravitational pull. And that wobble could be detected by measuring vanishingly small changes — the Doppler shift — in the star’s light waves. So Marcy got to work with a state-of-the-art spectrometer and a great deal of elbow grease and began to reduce the margin of error in measuring light waves. In 1995, he hit the astronomer’s equivalent of a mother lode.
He found not one but two planets orbiting distant stars, which he promptly announced at the January convention of the American Astronomical Society. It generated a response typical of many major scientific discoveries: mounting skepticism. But since then, Marcy and his team have found nearly 150 more and enough corroborating evidence for these planets to be accepted universally … well, almost.
So far, all of the planets found are considerably larger than Earth, and astronomers suspect none has an atmosphere like Earth’s. So the search continues today, because lying at the heart of this investigation is the big question: What else out there can, or does, support life?
“We have highly trained astrophysicists working on this problem, and yet it’s something so fundamental that a 5-year-old gets it,” Marcy said.
In the meantime, Marcy had another idea. He could apply the same method of spectrometry that found him so many planets to detecting laser lines.
At this point, we need to back up a bit to 1961, the year in which Nobel laureate physicist Charles Townes laid the groundwork for extraterrestrial lasers. Not coincidentally, Townes is also considered the father of the laser. In musing on the capabilities of intensely focused light in the post-Sputnik age, Townes delivered a paper in which he computed how much light would be received from a laser at various — astronomic — distances and concluded that laser technology would be the most likely means of communication for an advanced civilization.
“Everyone said at the time, ‘Oh yeah, that’s obvious,’” Marcy said. “But it has only been in the last few years that people have said, ‘Let’s follow up.’”
The follow-up research has employed a direct method of pointing a telescope at the sky and looking for pulsed optical lasers — a flash no more than a billionth of a second. Among the leading lights in this search are Dan Werthimer of UC Berkeley's Space Sciences Lab, Paul Horowitz at Harvard and Stuart A. Kingsley, all part of what's called Optical SETI.
Instead of trying to catch this flash directly, Marcy uses a spectrometer that will pick up any laser, pulsing or not. He takes 30-minute exposures of entire galaxies, which a spectrometer breaks into thousands of colors — think of it as shining the light of a galaxy through the world’s most differentiating prism, producing a spectrum of 100,000 different shades of the rainbow.
The good thing for Marcy, and the key to this method, is that lasers emit a single color of light. Shine a laser through this prism and you get one — and only one — color, just two or three pixels wide. Thus, a laser would be easily distinguished from starlight, which emits thousands of colors, as well as the sodium streetlamps of nearby San Jose, which produce a single smudge the color of smog.
“We’re looking for a dot at a specific wavelength at a specific place in the sky,” Marcy said.
Marcy’s strategy is to stay close — a relative term — gazing a mere 30 million light years away. “That’s out your back porch, cosmologically speaking,” he said, “one-thousandth the size of the visible universe.” Plus, he’s focusing at the center on entire galaxies — tens of billions of stars at a time, “any one of which might house a laser-toting civilization.”
Time constraints prevent him from analyzing data until July. And if he should get a result that looks promising, it would require considerably more thought, study and consultation in order to rule out all other possibilities. Marcy is nothing if not a very careful scientist.
Still, the question looms. What if Marcy becomes convinced that he has found a laser line? It would trigger a host of concerns: Can we communicate with extraterrestrials, and what can we learn? What have we learned already? Do they have a great galactic library of information that might be useful to us?
Then there are the issues of planetary security and the primary fear that probably lurks in the hearts of John and Jane Q. Earthling: Are they coming to get us?
Marcy stressed three things at this point of the discussion:
1. This is a very, very long shot.
2. Scientists would have to be sure that the discovery became publicly available — it couldn’t be bottled up by any government or any of its interested institutions, such as the military.
3. The average person would realize that we are “part of some galactic country club — just one species of perhaps many in the universe.”
In short, any such discovery would rip the top off most everything we know. So unbuckle those mental seat belts; you are now free to move about the universe.
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