New Call To Seek ET
By Looking For Flashes
Of Light In Distant Space
By Nicholas Booth
The Times - London
If ET is trying to contact us, he won't be phoning - he will use the powerful flashlights that are lasers to draw our attention. Like lighthouses on the unexplored seas of space, these unique flashes of laser light, which astronomers can detect with simple equipment, will soon tell us whether any stars are harbouring advanced civilisations.
That is the startling claim of the American inventor of the laser, Charles Townes, who has long urged his colleagues to look for such tell-tale signs of alien intelligence. All scientific searches to date have involved listening for radio signals from alien civilisations; now a team from the University of California at Berkeley will use a simple, antiquated telescope to try to spot the laser flashes.
At 83, Professor Townes, a Nobel prizewinner, is delighted to be vindicated. "I proposed this idea in the Sixties," he says. "Now a group of astronomers will start to make a search this autumn. I am very pleased."
This attempt is the start of a new era of astronomy. The method is, according to the astronomer in charge, "embarrassingly simple". Embarrassing because it could have been undertaken at any time in the past four decades, but Professor Townes's notion of looking, rather than listening, was largely ignored.
"If there are aliens sending us messages by laser, we will see them," says Dan Werthimer, the director of Berkeley's Search for Extraterrestrial Intelligence (SETI) programme.
Unlike the aliens in movies, who frequently speak English, the real ones would probably not use Morse code. "They would send very short, powerful pulses of laser light that would be unmistakable. It doesn't require that much energy to do," Dr Werthimer says.
Later this autumn, he and his colleagues will use a 30in telescope - modest by professional standards - at Mount Leuschner, about 20 miles east of Berkeley, to look for laser flashes. Light captured by the telescope will be split into two and fall on to photo-multiplier tubes, which will amplify the signal. If both see unusual flashes at specific wavelengths -lasting perhaps a few billionths of a second, with a power output greater than that of the stars they are looking at - they will have hit the jackpot.
Seeing signals in the two separate halves of the beam means that they could not be artefacts of the detection process.
Lasers are the only way that bursts of light could be sufficiently concentrated. As with the powerful search beams of a lighthouse, they could be directed to specific stars such as our Sun. Lasers work by exciting gas atoms and forcing them to give up their energy in the form of an intense flash of light.
"We could easily send a message into space to other civilisations," Professor Townes says. His Berkeley colleagues agree. According to Dr Werthimer, you could attach a simple laser to an optical telescope and direct it to nearby stars and send messages. "You could do that with a laser that transmits one megawatt," Dr Werthimer says. "That's about the same power as a television station."
But that is far into the future. For the moment, the Berkeley team is starting its own modest search; improbably, this optical work will cost just $20,000 (£11,400) a year, a sign of the times for SETI research. Searching for aliens has been criticised by some as a kind of wishful thinking, a subject without a science. And American legislators certainly agree: Nasa's ambitious program of SETI research using radio telescopes was cancelled in 1993.
However, with private funding from supporters such as the science fiction author Arthur C. Clarke and the film director Steven Spielberg, SETI struggles on.
Others have said that finding evidence for alien civilisation will be impossible. A similar thing was said to Professor Townes during the late 1940s after he proposed the forerunner of the laser, the maser (which produces microwave radiation rather than light). As a researcher at Bell Labs in New Jersey, he was a world expert on microwave spectroscopy, the probing of gases using radio waves. He realised that by using molecules to amplify signals, he could generate a powerful source of radiation. After he discussed the method in a scientific journal 50 years ago, "more than one Nobel laureate said it would never work. It was viewed as a crazy, cute idea and there wasn't much to it."
Early one spring morning in 1951, while sitting on a park bench in Washington, Professor Townes had what he calls "divine inspiration" of how to make a maser work and its possible applications. "I recognised that it could be a sensitive amplifier or atomic clock," he says.
Throughout the 1950s, the wavelengths used to probe gases were made progressively shorter - so much so that he could get down to optical wavelengths. Together with his brother-in-law, Arthur Schawlow, he developed the laser. Accordingly, Townes won the Nobel Prize in 1964 (along with two Russians who had independently come across the same principle). Lasers can now be found everywhere, from supermarkets to home CD players to hospitals.
"It comes home to me when I hear of friends who have had their sight restored," Professor Townes says. "To me, it was clear that the most important uses would come from connecting up optics and electronics."
Proof positive comes from the telescope now being used by Dr Werthimer's team (it is normally used to train Berkeley undergraduates). In 1959 - the same year in which a workable maser was developed - two radio astronomers declared that detecting radio signals would be the only way to find aliens. As a result, the scientific community tended to dismiss any other wavelengths that could be used to send messages.
By the mid-1960s, Professor Townes had moved to Berkeley and was working at the Space Science lab. By then, his idea was bolstered by the discovery of naturally existing masers in space. There are vast clouds of gas between the stars which can act as masers. Their constituent molecules are naturally excited to such an extent that they amplify microwaves across the vast firmament of the heavens.
Any sufficiently advanced alien civilisation would be well aware of that and could emulate the process. Professor Townes points out that these clouds have been emitting intense radiation in all directions, but it was only recently that humanity has acknowledged their existence.
"If we'd have found them earlier, then we could have developed the laser sooner," Professor Townes says. "We didn't look. Other civilisations might have taken their cue from natural masers in space."
This autumn, the Berkeley group will systematically look at 2,500 nearby stars. The criterion is fairly simple: they will be Sun-like stars, around which planets like ours - and corresponding civilisations - could have evolved.
All involved agree that the search is a long shot, with truly astronomical odds against it.
But the final word goes to Professor Townes, who insists that, as with the invention of the laser, the discovery of life in space is simply a matter of looking hard enough.
"We don't know what we will find, so we must keep looking."
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