Beyond relativity

Sorry folks: Prospect has asked that my latest piece in the February issue, a survey of the centenary year of general relativity, remains "premium content" - which means I can offer only a teaser here. (Cue debate about paywalls and blogs - but we've all got to survive...) I'll be putting up some more on this topic soon, though.

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One hundred years ago, Albert Einstein presented a paper to the Prussian Academy of Sciences that explained gravity. It is one of the four fundamental forces in the universe, although in 1915 only one of the others – the electromagnetic force – was known. (The other two act inside the atomic nucleus.) But Einstein’s paper offered a radically different way of thinking about gravity. Rather than being an invisible force between two massive objects, he described it a distortion induced by the masses in the very fabric of time and space (spacetime). This warping dictates the paths that objects take under gravity’s influence: Newton’s apple fell to earth because it was, in effect, slipping down the slope of bent spacetime. In the curved space around the sun, the planets execute orbits rather like marbles running around the rim of a bowl.

This geometric interpretation of gravity is the central idea of Einstein’s theory of general relativity. It is widely considered to be not only his greatest intellectual achievement but also the epitome of a beautiful theory. Ernest Rutherford said that the theory “cannot but be regarded as a magnificent work of art”, and Einstein was not shy of advertising its virtues himself: “Scarcely anyone who fully understands this theory can escape from its magic”, he wrote.

But the centenary celebrations for general relativity will not simply be looking back. For 2015 will be a banner year for some big, ambitious experiments that aim to probe the theory. They are looking for one of the most spectacular of the theory’s predictions: ripples in spacetime called gravitational waves...

[The rest will be on Prospect's site very shortly.]