The Great Telescope Race

High above the Earth, a gargantuan telescope peers into space. It dwarfs the Hubble Telescope, the twentieth-century's greatest scientific instrument. With a mirror half the size of a tennis court, the Next Generation Space Telescope will reveal the edges of the observable Universe.

The Next Generation Space Telescope is already on the drawing board. Within 10 years, this ultimate telescope will be flying in space. Instead of orbiting the Earth, the Next Generation Space Telescope will follow its own orbit around the Sun. But its designers will place it at a special balance point, outside Earth's own orbit. At this location, the so-called Lagrangian-2 point, our planet's gravity still ensnares the telescope, so it travels round the Sun always a million miles from the Earth.

Huge solar panels will provide the telescope with power, and - just as important - shield it from the Sun's heat. Cooled down to the temperature of deep space, the Next Generation Space Telescope can observe faint heat signals from the farthest reaches of the Universe. It will peer beyond where even Hubble can see, to the very edges of the observable Universe.

Because light takes billions of years to travel this far, the Next Generation Space Telescope will be seeing these distant regions as they were billions of years ago - just after the Big Bang in which everything began.

This ultimate telescope combines the clear views that Hubble enjoys with the mammoth size of the biggest telescopes currently being built on the ground.

In the dry deserts of Chile, astronomers are this year completing the most powerful telescope ever constructed on Earth. The Very Large Telescope in fact comprises four telescopes, on the peak of a mountain that has been blasted flat to form a platform for the cosmic quartet. Each of the telescopes has a mirror 8 metres (26 feet) across. Linked together, the four instruments will collect as much light as a single telescope over 50 feet in size.

Three of the four telescopes are already working, and astronomers have been astounded by the quality of their views of the cosmos - of glowing nebulae, dying stars and distant galaxies.

To construct such a vast telescope, its builders have pushed engineering to the limit. In particular, the telescope must tilt to turn to different galaxies, giving gravity a purchase on its huge - but thin - mirror. If gravity bends the mirror by an amount smaller than the width of a human hair, the telescope's view of giant galaxies is blurred to uselessness. So the designers have attached the back of the mirror to hundreds of moving supports, computer-controlled to push the mirror back into shape - a millionth of an inch at a time - as the telescope tilts.