Comment: The final frontier of science

GALILEO MAY not have been the first person to look at the night sky with a telescope, but he was certainly the first to write about it - mythologising him for ever as the man who invented modern astronomy. The small instrument he used in 1610 bears little resemblance to the mirrored Cyclops on an Hawaiian mountain which opened its eye yesterday to capture a view of the heavens that Galileo could only dream about.

The Gemini North telescope on Mauna Kea (a Gemini South is being built in Chile to watch the southern sky) is a monolithic tribute to the advances made in astronomical observations at the end of the 20th century. It will be able to distinguish two points of light in the night sky that are separated by an angle of less than a tenth of an arc second - equivalent to identifying a 10p coin in Oxford while standing on Hampstead Heath.

Its huge light-collecting mirror - 8.1 metres in diameter - will enable astronomers to view the faintest astronomical objects in the most distant reaches of deep space. Gemini will, like the Hubble space telescope, enable scientists to look back in time to events that happened billions of years ago - the time it has taken for the light to reach Earth. Gemini provides us with a time machine to see where we have come from, and give us some insight into where we are heading.

"Astronomy is about origins," explains Professor Malcolm Longair, a distinguished astronomer who is a member of the Gemini team. "We want to study the origins of the universe, the origins and galaxies, stars and planets and even the origins of life itself."

Such original science, however, does not come cheap. Gemini North alone cost pounds 115m to build, although this is chicken-feed compared to the pounds 1bn spent on putting the Hubble telescope into space.

Part of the expense is to do with the necessarily isolationist nature of the building projects. Ground telescopes see more from mountain-tops, and can work to full effect only if they are as far away from sources of light pollution (towns and cities) as possible.

Another part of the cost is the enormous technical difficulty of building a lumbering leviathan that operates as precisely as a brain surgeon. The Gemini North telescope weighs about 340 tons, 20 of which are accounted for by the ground-glass surface of the main mirror.

Practically all those hundreds of tons of concrete, steel and computer equipment are designed to control the fine, aluminium coating of the mirror's reflective surface.

As Dr Paul Murdin, of the astronomy research council, put it: "It's like getting Arnold Schwarzenegger to do a pas de deux with the grace of a Nureyev."

The Hubble telescope has the added advantage of operating in the airless environment of space. The starlight it juggles with is pristine and devoid of the interfering effects of the Earth's atmosphere.

Gemini is among the first ground-based telescopes to correct the distortion with an intricate system of "adaptive optics". Computer equipment calculates the amount of distortion caused by atmospheric disturbances and subtracts it from the final analysis, with the result that the first images produced by Gemini are already as distinct - if not more so - than the famous pictures from the Hubble.

Telescope engineers and astronomers are waging a new kind of space race, with the ground-based scientists working out better ways of overcoming the limitations of operating on terra firma and dealing with atmospheric disturbances, while the space-based astronomers are busy devising bigger but more lightweight mirrors to put in orbit.

Already there are serious plans to build the Next Generation Space Telescope (NGST), the successor to Hubble, which is scheduled to be launched in 2007, and should be able to gather 10 times as much light with a folding, lightweight mirror. Not to be outdone, the ground-based astronomers are working on their own plans to build the Overwhelmingly Large Telescope (I kid you not) which could have a mirror as much as 100 metres in diameter.

Size, it seems, means a lot in astronomy because the bigger the mirror or aperture, the greater the amount of light the telescope can harvest - meaning that the faintest objects in space can be seen. The NGST is expected to see objects that are 400 times fainter than the faintest star or galaxy that can be seen with Hubble. The American space agency believes that its next space telescope will be able to see events that occurred less than a billion years after the Big Bang, when time and matter itself came into existence in a gigantic explosion.

Like the Hubble, future telescopes will be able be able to witness the very act of creation, when the molecules we are made of were formed in the white heat of the stellar furnaces.

As one astronomer working on the NGST put it: "We expect to see the birth of stars and galaxies. We will witness the act of creating the very stuff we are made of."

Perhaps most ambitious of all will be the attempts of astronomers to use future telescopes to detect the tell-tale signs of extraterrestrial life. Already the Hubble has provided the vital signs of Earth-like planets orbiting distant stars.

Future observations may be able to detect the definitive signs of water on some of those planets, which will significantly raise the possibility of there being life in other solar systems.

Practically every civilisation has had a fascination with the stars, and undoubtedly much of this interest has been driven by the desire to know what lies beyond the Earth. The Babylonians and ancient Chinese kept detailed records of the movements of the Moon and planets against a stellar backdrop and the Greeks and Arabs used hand-held devices for measuring the angle of the stars above the horizon, and were thus able to estimate the time of night.

Galileo's efforts to continue the tradition of star-gazing famously brought him into conflict with the Church over whether the Sun went round the Earth, or the Earth went round the Sun. By the time Galileo published his heliocentric view of the universe in 1632, it had already been suggested at least three times in history - by Aristarchus in the third century BC, by Copernicus in 1543 and by Kepler (who proved it) in 1609. Yet it was Galileo who is popularly remembered as the pioneer of the view of the Earth moving around the Sun, largely because he was forced to retract it by the Inquisition in 1633.

Galileo was probably the first person to see the rings of Saturn, using his rudimentary telescope, although his eyepiece was not good enough to resolve precisely what they were.

He came to the conclusion that the two ear-like extensions of Saturn were additional planets on each side. No doubt astronomers at the end of the 21st century will look upon Gemini's efforts to resolve the faintest points of light in its view-finder with equal amusement.

"We are constantly finding new ways of doing things better," explained Dr Murdin yesterday, when the first images from Gemini were placed on the Internet.

It takes years to plan a new Gemini or Hubble and more than a decade to build one. Yet the mission to build bigger and better ways of seeing the stars goes on unabated, save for the small problem that someone, somewhere, has to pay for it all. It's a mission that has no limits or end in sight; it is as infinite as space itself.