Leading Article: Reaching for stars is good for life on Earth

THE END of the world is probably not nigh, but you can't be quite sure. Today, Comet Shoemaker-Levy 9 will start crashing into Jupiter with the force of 10 million H-bombs. Like a benign cosmic fisherman, Jupiter has drawn the comet into its gravitational net, absorbing the blow for the common good. But it can also knock other comets off course, increasing their chances of coming our way. And if they do not, space is full of hurtling objects that may do so another day. Earth is not safe, and never has been. Evidence for past collisions is mounting.

There is not a lot we can do about it, although Edward Teller has suggested preparing nuclear weapons to shoot down incoming comets. The main effect, like that of most space travel, is on our consciousness. The first pictures taken of Earth from the Moon (the 25th anniversary of the landing is next week) made many people truly aware for the first time that this planet is a small, vulnerable, very beautiful object apparently alone among its visible neighbours in being blessed with life. Today's event pushes us to take another conceptual step to a point from which Earth looks even smaller. Seen from beyond Jupiter, the impact of 10 million H-bombs on this planet might be barely detectable. Our end would be no more than a tiny blip, at most.

As the millennium draws to a close, such thoughts will stimulate a growth industry among those who relish the idea of catastrophe for personal or ostensibly religious reasons. Comets have long been seen as harbingers of bad news, and warnings of the end of the world have been common among preachers and madmen for as long as records go back. Now, respectable astronomers have begun to join them. One day, inevitably, one of them will be right. In the meantime, it is to be hoped that few people give away all their money in anticipation, as did members of a Korean sect two years ago.

But these warnings can also have more positive effects. From the distant perspectives of space, most of the wars and quarrels of the world seem as meaningless as drunken brawls in a pub. It is the oneness of the human race, clinging to its precarious blob of matter in a huge void, that impresses itself on the mind.

Other modern developments are pointing in the same direction. Probably the most important bit of scientific progress to be accelerated by the space race during the Cold War was not the much-mentioned non-stick saucepan but communications. These, too, are shrinking the globe as they surround it with satellites and lace it with electronic highways carrying words, pictures, music and financial transactions almost instantly. As a result, we may be passing through a period of changing perceptions as significant as that provoked by the discoveries that the Earth is round and that it revolves around the Sun. Obviously this will not end wars. Even the most intimate villages can be riven by feuds and shattered by domestic violence. But there is at least a good chance that the need for co- operation will gradually become evident to more people more often.

This provides an unverifiable but appealing justification for continuing to spend money on the exploration of space. Of course the scientific advances made in the space race would have been made eventually without it. Of course, too, the manifold miseries of life on Earth make the first call on funds and attention. Nor are there any easy ways of deciding how much money it is right to spend on space, or how it should be allocated.

But if the human race stops reaching out beyond the confines of its own planet to explore the larger questions about its origins, its place in the universe and its likely future it will stultify its curiosity and development in ways likely to have negative results in many other areas. The appeal of space to the imagination should not represent an escape from terrestrial problems but the search for new ways of looking at them.