Plate tectonics: in memory of Britain's greatest rock stars Like all great scientific ideas, plate tectonics is, in essence, simple. Molten rock welling up from the deep crust reaches the surface at the mid-ocean ridges. As it cools, it adds new material to the plates on either side, as they separate at a rate of a few centimetres a year. Meanwhile, at the deep ocean trenches, crustal rock sinks back into the mantle, completing the conveyor belt cycle. These plate boundaries - one "constructive" and the other "destructive" - are associated with volcanism, earthquakes, and mountain-building; the slow movement of the plates causes the stately march of the great land masses in continental drift. In short, plate tectonics explains at a stroke all the important geological phenomena on Earth. Unsurprisingly, the scientific establishment was sceptical. Vine spent a year or two touring the world, explaining to geologists twice his age where they and their predecessors had gone so badly wrong for so many decades. But in 1966, Maurice Ewing, the dictatorial head of the prestigious Lamont-Doherty Oceanographic Institution in New York, asked Vine's head of department, Sir Edward Bullard: "You don't believe all this rubbish, do you Teddy?" As late as 1970, the prominent "fixist" geologist A A Meyerhoff claimed that "sea-floor spreading and continental drift - as presently conceived - belong more properly in the realm of mythology than in the science of geology." Yet even though their theories have transformed geology as surely as Watson and Crick's did biology - immeasurably enhancing our understanding of earthquakes, volcanic eruptions and tsunamis, and guiding our exploration for oil, gas and minerals - Vine and Matthews have faded from public memory, if they ever lodged there in the first place. That is surely unfair. Where Crick and Watson could march into the Eagle pub declaring that they had found "the secret of life," they had really only established the molecular structure that provided a mechanism for something known about since Darwin. Vine and Matthews could fairly claim to have discovered "the secret of the Earth" - the mechanism that makes this planet unique in the solar system and, ultimately, suitable for life. For plate tectonics explains not only why continents move and mountains rise, but why the climate changes, and how the course of evolution is set. The movement of the continents, it turns out, is merely the surface manifestation of a great convection system that cycles material throughout the Earth's mantle, right down to its iron core. This, we now know, has all sorts of consequences that make the Earth habitable: our rocky neighbours, Mercury, Venus and Mars, do not have plate tectonics and this in turn leads them, perhaps, to be inimical to life. If, as it now seems, life is rare in the cosmos, then it may very likely be because plate tectonics is rare. Without it, there would be no continents, no plants, no animals, no humanity. Watson and Crick may have discovered the secret of life, but it was Vine and Matthews who discovered the secret that made that life possible. Dr Roy Livermore is an associate lecturer at the Open University