Tuning into E. T.
HAT CREEK, Calif. –In this remote volcanic valley near Mount Shasta, 42 radio telescope dishes have sprouted amid the soaring ponderosa pines, listening for a voice from outer space.
Every few seconds, the 20-foot-wide dishes, scattered over dozens of acres, pirouette in perfect synchronicity. Astronomer Rick Forster said that after fine-tuning the dishes to function as a single giant ear, the real show will begin: listening for E. T.
When the full 350-dish array is completed in the next few years, Hat Creek Radio Observatory will be the biggest radio telescope in the world designed to search for extraterrestrial intelligence.
“It’s nuts to think we’re alone,” said Forster, 59. He works with the SETI Institute and the University of California, Berkeley, which are jointly installing the radio telescope dishes. “It’s just a matter of looking in the right direction, at the right time, at the right frequency, with the right algorithm,” Forster said.
Over the past few decades, researchers for SETI (Search for Extraterrestrial Intelligence) have relied on borrowed telescope time to scan 1,000 stars for signals from a technologically advanced culture. The new dishes, funded by a $30- million gift from Microsoft Corp. co-founder Paul Allen, will enable researchers to scan a million stars over 10 billion radio channels.
“The cosmic haystack is about to get enormously bigger,” said Jill Tarter, director of SETI’s research department.
Tarter declined to estimate the odds that this new effort will uncover an alien civilization. But she has a sense of excitement as the new telescope prepares to sweep the heavens for beeps and burps that could signal intelligence. “It’s hard to imagine how stupendous it would feel to find something,” Tarter, 64, said in an interview at SETI’s Mountain View headquarters.
Tarter has spent more than four decades –her entire career –trying to answer the are-we-alone question.
“If we find a second technological civilization, we will know there are many,” she said. “It’s also possible we are unique.”
To operate effectively, a radio telescope must be far from human civilization, which produces interference from television, radio and cell phones. At 3,500 feet above sea level, Hat Creek is surrounded by volcanic peaks containing enough magnesium to absorb human radio broadcasts. To catch a signal from outer space, you either have to build an enormous dish, like the 1,000-foot-diameter Arecibo facility in Puerto Rico, or connect many smaller dishes, like New Mexico’s Very Large Array, which has 27 dishes, each 82 feet across.
At Hat Creek, computers will combine the data from 350 dishes to produce, in effect, a single giant radio telescope. “What we’re doing is creating a big dish, 90 acres across,” Forster said. Even with this technology, SETI scientists acknowledge it’s a quixotic quest.
On a recent afternoon, senior astronomer Seth Shostak, 64, was showing a visitor around SETI’s headquarters when a white-haired man rushed by.
“This is Frank Drake,” Shostak said. Drake, a celebrated astronomer and astrophysicist, not only mounted what might have been the first serious experiment to search for aliens, he also created the landmark Drake Equation, a set of mathematical assumptions that attempts to predict how many advanced civilizations might exist in our Milky Way galaxy.
Some researchers have suggested that the answer could be up to 1 million. Drake’s answer? Ten-thousand alien civilizations in a galaxy of 100 billion stars.
Drake made his first attempt in 1960, using an 85-foot diameter antenna at the National Radio Astronomy Observatory in West Virginia.
Radio waves long have been considered ideal for communication with alien civilizations because the waves are easy to produce and receive, which is why humans use them on Earth to carry television and radio signals. They also penetrate the gas and dust between stars.
Drake pointed the antenna at two nearby stars, Epsilon Eridani and Tau Ceti –virtually next-door neighbors in galactic terms at just over 10 light-years from Earth.
In April 1960, Drake picked up a signal. His first thought, according to Shostak, was: “Can it be this easy?”
The second was, “Holy cow, what do I do now?”
“It wasn’t that easy,” said Shostak, who is writing a book about the search for alien intelligence.
Drake, now 78, had mistaken a passing aircraft for an alien broadcast. It was the first of many false alarms, presenting a problem that persists today: separating human and natural radio signals from the signal of an alien civilization.
Shostak calls it the “E. T. or AT&T?” problem.
So how does one tune in to intergalactic radio?
It’s a lot more complicated than pointing the antenna at the right star, just as tuning in a radio station on Earth requires listeners to spin the dial.
The radio spectrum ranges over frequencies of 3 kilohertz (3,000 hertz) to 300 gigahertz (300 billion hertz). An alien signal could be hiding anywhere in between.
With the Hat Creek array, SETI will be able to scan a much broader range than before: everything from 0.5 gigahertz to 11 gigahertz, a range of 10 billion channels.
When they get a promising signal, the real work begins. The key test, according to Tarter, is the band width. Nothing in nature produces signals narrower than 300 hertz.
“Quasars, pulsars, things like that make signals much broader,” Shostak said. “A narrow signal must have been produced by a transmitter.”
Over nearly 40 years of searching, no signal has panned out to be anything more than a satellite transmission or some mundane natural pulse.
But the time period is deceptive. Actual search time added together amounts to only 18 months, Shostak said, hardly enough to conclude that our galactic kin either are not there or are not interested.
