From time immemorial, scientists have had a weakness for experiments with mirrors. Archimedes, for example, well known to the marine community for his discoveries in the bath, is said to have deployed mirrors as a weapon at the siege of Syracuse.
He used the polished shields of the local troops to focus rays of sunshine on the invading Roman fleet. By this means, or so the story goes, Archimedes "kindled a great flame, the whole of which he directed at the ships at anchor in the path of the fire, until he had consumed them every one".
Unfortunately, modern scientists have calculated that it would require 500 polished metal shields to succeed in igniting even a single twig, so the kindling of a whole armada seems unlikely. In any event, history records that the Romans actually captured Syracuse in 212 BC, killing poor Archimedes in the process. More recently, another brilliant wheeze concerned the use of mirrors to combat the dreaded greenhouse effect. By placing a highly polished surface on the ground, it was argued, it should be possible to reduce the net absorption of solar radiation in its vicinity by 10 per cent or more.
Some scientists, indeed, have gone so far as to calculate how many mirrors would be required to counteract the anticipated global warming. If, for example, an individual were to feel it sufficient only to neutralise his own personal share of the enhanced greenhouse effect - about one five-billionth of the total - he would need, we are told, some 150 square yards of mirror in his back garden.
This, of course, applies only at the latitude of Ireland; conscientious residents of, say, the vicinity of the Sahara would need a mere 20 square yards of reflecting surface to discharge their duty to posterity.
But perhaps the most imaginative suggestion as to the potential use of mirrors has been the theory that they could be used to deflect the path of rogue asteroids, should any be discovered heading in our direction, posing a risk to planet Earth.
The theory is that, if danger threatened, a giant mirror would be launched into space in such a way as to follow the asteroid along its track. As the two travelled side by side through space, sunlight focused by the mirror on to the offending missile would evaporate loose silicate rocks or lumps of ice upon the surface of the asteroid. This would result in jets of gas that would act as thrusters, thereby generating a steady push to nudge the threatening cosmic body to one side.