Is There Anyone Out There?

If there is intelligent life somewhere out there, the world's largest radio telescope, among the mountains of Puerto Rico, will help find it

  • The massive reflecting dish at the Arecibo Observatory can be seen clearly from a jumbo jet at 33,000 feet. Photograph by National Astronomy and Ionosphere Center
  • The platform is suspended to receive the signals it collects. Photograph by National Astronomy and Ionosphere Center
  • Signals in space: at the SETI (Search for Extra Terrestrial Intelligence) Institute, 15 million radio frequencies are monitored every second. Photograph by SETI Institute/Science Photo Library
  • Beneath the giant Arecibo dish, earthly life goes on. Photograph by Larry Luxner
  • The M-13 star cluster in the constellation Hercules, 100 light years across and containing half a million stars, was the target of the famous message transmitted from Arecibo in 1974; but it will take 22,500 years, travelling at the speed of light, to get there. Photograph by Seti Institute/ Science Photo Library
  • Stars in the making: the Orion Nebula, 1,600 light years away, a brilliant cloud of gas and dust where new stars are being formed. Photograph by Noao/ Science Library
  • Above the massive reflecting dish is a 600-ton telescope platform, which is suspended to receive the signals it collects. Photograph by the National Astronomy and Ionosphere Centre
  • The massive reflecting dish at the Arecibo Observatory can be seen clearly from a jumbo jet at 33,000 feet. Photograph by the National Astronomy and Ionosphere Centre
  • One day antennae like this will do the same from an orbit around the earth. Photograph Dr Seth Shostak/ Science Photo Library

Hidden among the karst mountains of north-western Puerto Rico, where the chirping of coqui frogs fill the moist night air and stars shine undistracted by city lights, sits the most sensitive radio telescope on earth.

The Arecibo Observatory is so huge you can see it from a jumbo jet at 33,000 feet. Yet it’s so obscured at ground level that first-time visitors, searching down the road near the world famous Camuy caves, need a detailed map to find the only road leading to its guarded entrance.

Recently, the Observatory was in the scientific headlines once again when one of its scientists announced the first proof of the existence of planets outside our own solar system. By timing the arrival of radio signals from a distant star known as PSR1257+12, Polish astronomer Alexander Wolszczan was able to detect the presence of two or possibly three planets in orbit around it. The planets are three to four times as massive as our own earth, though PSR1257+12 – a pulsar – is a miniscule five miles in diameter, only 0.000014 the size of our sun.

Daniel Altschular, the Observatory’s Uruguayan-born director, said Wolszcan’s discovery came a few months after British astronomers had had to withdraw similar findings as invalid. “With the withdrawal of the British results, ours is the only evidence of extrasolar planets. We are quite certain our results will stand.

”T he Arecibo Observatory is funded by an annual US$7.5 million grant from the National Science Foundation, though Cornell University has administered the site ever since the Observatory was built in 1960. At any given time, there are 140 full-time staff, including visiting astronomers from countries as diverse as Argentina and Bulgaria, Russia and Brazil.

Major discoveries about quasars and pulsars, about the nature of the ionosphere and of neighbouring planets (Mercury, Venus, Mars) have been made at Arecibo. “What is done and not done here is determined by the international scientific community,” Altschuler says. “Right now, the two largest uses have to do with pulsars and extra-galactic spectroscopy, or the detection of radiation produced by neutral hydrogen. Since the universe is composed mainly of hydrogen, this is very important. Our smaller projects include the study of stars, molecular clouds in our own galaxy, and ionospheric physics.”

The Arecibo “dish”, suspended over a huge natural sinkhole, is by far the largest of its kind in the world. With a diameter of 304 metres, it covers 20 acres and consists of nearly 40,000 perforated aluminium mesh panels, each measuring one metre by two. A 600-ton receiving platform is suspended 130 metres over the dish by 12 cables strung from three reinforced concrete towers. Underneath the dish lies a jungle of ferns, orchids and begonias, though few outsiders ever get a glimpse of this unusual garden.

Tourists who visit the Observatory only get as far as a viewing platform high above the site; the dish itself is off-limits. But the whole complex is set to become more tourist-friendly, thanks to a $1.7 million development project that will include a visitor centre and an exhibit on radio astronomy in both English and Spanish.

Altschuler says there are no military secrets at the Observatory. The security apparatus is there simply to guard against terrorism. “Before it became a national facility, it was funded by the Department of Defense. Since (the National Science Foundation) took it over, it’s not in any way related to the military.”

The Arecibo Observatory owes its existence largely to Puerto Rico’s status as a Commonwealth of the United States, and to its lucky position only 17 degrees north of the equator. “The planets are mainly in the equatorial plane of the earth,” Altschuler explains. “You want to be as close to the Equator as possible for a good fraction of the time. Some objects are so weak they cannot be seen optically, so radio astronomy is a complement to optical astronomy. Ours is the most sensitive instrument in the world.”

So sensitive, in fact, that the Arecibo dish can detect quasars 13 billion light years away, just by systematically probing the depths of the universe with radio transmitters set at specific wavelengths and listening for the echoes.

In conjunction with Arecibo, NASA (the United States National Space Agency) is sponsoring a programme to study the space environment around our own planet. That project — Combined Release and Radiation Effects Satellites — involves releasing sodium, barium, lithium and other gases into space, forming red and purple clouds that help to paint a picture of the earth’s magnetic field, which is otherwise invisible.

To help corroborate the data, NASA has used small optical and radio tracking stations in Argentina, Chile and Ecuador, as well as the Caribbean islands of Anguilla, Aruba, Guadeloupe and Dominica.

On nearby St Croix, in the United States Virgin Islands, scientists have completed another kind of radio dish. This one measures 25 metres in diameter, and is part of the Very Large Array of ten such stations strung across 8,000 kilometres from the Caribbean to Hawaii. The network of stations, funded by the National Science Foundation and operated by the National Radio Astronomy Observatory in Socorro, New Mexico, will give astronomers the equivalent of a radio telescope with a dish 8,000 kilometres across.

“It improves the resolution and visual acuity by being large,” says John A. Williams who helps maintain the 8 million facility. “The resolution provided by that kind of dish is like being in San Francisco and being able to read a newspaper in New York.”

But one of Arecibo’s most intriguing functions is the search for life outside our own solar system. On October 12 last year, the 500th anniversary of Columbus’s arrival in the “new world”, Arecibo became part of NASA’s $100 million Search for Extra-Terrestrial Intelligence (SETI) programme, the High Resolution Microwave Survey.

This is not the first time that Arecibo has acted as a gigantic message centre for life elsewhere in the universe. In 1974, a famous transmission — the Arecibo Interstellar Message — was beamed to M-13, a globular star cluster some 25,000 light years away. That signal contained 1,679 bits of information on everything from the chemical make-up of our atmosphere to Earth’s position in the solar system.

But the new NASA programme is much more ambitious. It systematically scans the sky for radio transmissions deliberately or inadvertently broadcast in our direction by civilisations elsewhere in the universe.

“This project,” said a recent NASA press release, “will accomplish more searching in the first few minutes than in the combined total of all previous searches.”

But at Arecibo, Altschuler is less than excited about the SETI possibilities. “In the future, there will be new NASA- sponsored SETI projects, and Arecibo will take part in these observations. But it’s a very minor area of research, and the general topic of UFOs is of no interest to us. Sending out signals is a purely symbolic act.”

Do We Really Want to Know?

Arecibo produces the strongest radio signal that can be transmitted from our planet; it could be picked up by a similar instrument anywhere in our Milky Way galaxy with its 200 billion stars.

The message transmitted from Arecibo in 1974 towards the giant star cluster M13 in Hercules is still only at the beginning of its 25,000-year journey. It described the bio-chemistry of our planet and the location and status of human civilisation; the astronomer Carl Sagan was among the scientists responsible (others have begun to think that, given the unerring tendency of our own species towards conflict, it would be a lot wiser to keep quiet in our comer of the universe and not let anyone else know we’re here in case they share our own tastes for war and destruction).

Statistically, the odds must favour the development of intelligent life elsewhere in the universe. Ours is only one of billions of galaxies, each with billions of stars: is it conceivable that nowhere else are there planetary systems and planets capable of sustaining intelligent life! Where conditions for life exist — planets, water and billions of years — life should develop.

So NASA programmes are scanning the universe for planets like our own, particularly within: 75 light years of earth, and are also scanning vast ranges of radio frequencies with computers that can monitor ten million channels at once. They are searching for a signal that seems constant or at least drifting slowly, and that is separate from the transmissions of quasars and pulsars. Arecibo is part of this search. So far, nobody has turned up any evidence of life with advanced technology capable of interstellar radio contact.

But it is early days yet. We only developed radio a century ago. For only 40 years or so have bizarre images of life on earth — I Love Lucy, The Fugitive, ads for soap powders — been travelling into space, ready to bemuse any civilisations they may happen to reach. The first serious attempt to listen for radio signals from two nearby stars only began in 1960. The Arecibo message to M13 was transmitted less than 20 years ago. The Viking missions to Mars began only in 1976; only now are spacecraft heading beyond the solar system (like Pioneer 10) carrying audio tapes and pictures.

So it has taken perhaps 4 billion years for life on this planet to develop to the point of discovering radio technology. Many scientists feel the time between advanced technological discovery and the destruction of the species may well be small, the window for peaceful interstellar exploration narrow.

And it may be that there are very few colonies of advanced intelligent life in the universe, and none in our own galaxy, so that the nearest are many thousands or millions of light years away. Perhaps our own planet is a freak, and the rest of the universe is simply empty of intelligent life.

But who can resist wanting to find out?


– Jeremy Taylor

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