The Economist explains Cosmic inflation

MENTION inflation and most people will think of something that erodes the value of their bank balances. A cosmologist, however, may think instead of the beginning of all things­—for, though no one knows how the universe started, they do know, or believe they know, what happened a trillionth of a trillionth of a trillionth of a second later. And on March 17th the first actual evidence of this belief, which is known as inflation, was announced, thus backing up the theory, promulgated three decades ago by Alan Guth and Andre Linde.

The amount of inflation Dr Guth and Dr Linde predict is extraordinary. They suggest the universe became 10 billion billion billion times bigger almost instantly. Their theory’s purpose is to iron out, almost literally, two cosmological difficulties. These are that observations have shown that space is flat (think Euclid, and parallel lines never meeting), and that matter, on a cosmic scale, is evenly distributed. Both, though true, are unlikely. There is only one way to be flat, but an infinite number to be curved. And there are likewise many more ways to be randomly than evenly distributed. Inflation on the scale described by Dr Guth and Dr Linde would stretch any curvature in space so far that, to all intents and purposes it was flat, and similarly smooth out the distribution of matter.

The discovery which suggests all this is real was made using a special telescope at the South Pole. This detected faint irregularities in the microwave radiation left over from the universe’s beginning—irregularities which match those the theory predicts would have been created by the gravitational waves generated by inflation. Dr Guth and Dr Linde are understandably pleased.

There is, though, a big potential consequence. Gravitational waves are described by the general theory of relativity. Those created by inflation, however, were also quantum effects because the universe was so small when inflation began that it was a quantum phenomenon. General relativity and quantum theory, though both true as far as any experiment yet done can show, do not connect mathematically. Primordial gravitational waves from the cosmic inflation are the first empirical connection between them, and may thus point the way, at last, to a unified theory of physics. And that really is a big deal.

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