The Earth is round, as Christopher Columbus showed more than 500 years ago. But cosmologists have now demonstrated that the universe is almost certainly flat, which means it is full of a mysterious "dark energy" and will continue expanding for ever.
Though on Earth we are used to flat surfaces, where normal Euclidean rules of geometry apply, scientists have suspected for decades that space might follow different rules, in which space is curved, so that the shortest distance between two points is actually a curved line rather than a straight one and apparently parallel lines would eventually meet, like lines of longitude on a globe.
Such as idea was put forward by Albert Einstein, who proposed the idea of a non-Euclidean universe in his theory of general relativity, one of the greatest pieces of physics of the 20th century. He even included an extra "curvature" factor into his equations to make them agree with that viewpoint.
But now a team of American, Italian, Canadian and British cosmologists has published data in the science journal Nature which seem to confirm once and for all that we live in a "flat" universe. The findings come from the first detailed study of the Cosmic Microwave Background (CMB), an afterglow of ancient radiation left over from the Big Bang which created the universe between 15 and 20 billion years ago. Images of the CMB were obtained using a telescope suspended from a balloon almost 120,000ft above the Antarctic.
The project, which was called Boomerang (Balloon Observations of Millimetric Extragalactic Radiation and Geophysics), mapped minute temperature fluctuations that corresponded to structures in the early universe which predate the first star or galaxy.
But according to Andy Fabian, of the Institute of Astronomy at Cambridge, the finding has an odd side-effect: it means empty space is full of energy. "The good thing about this finding is that it means the beginning of the universe didn't have to be so precise, as if the universe was curved - that backs up our theories very well. But it also implies that there's a lot of 'dark energy' out there, which means the vacuum of space, down at the atomic level, has energy and pressure pushing everything in the universe apart."
However, this peculiar dark energy will not be easy to harness, if it ever can be, since it operates at the atomic and subatomic level. "You won't just be able to pump all the air out of a can and get it to expand infinitely," said Professor Fabian. "It's very hard to know how you can use it. But I think it's very exciting that here, at the beginning of a new century, we have this wonderful new problem to understand."
The data also imply the universe will go on expanding for ever rather than eventually collapsing into a "Big Crunch".
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