Everything visible today once fit inside a speck far smaller than an atom
All the matter and energy in every galaxy we can see was, in the first instant, squeezed into a region trillions of times smaller than a proton. Then space itself ballooned, doubling again and again until that region was under a metre across. Cosmologists call this frantic growth spurt inflation, and it answers puzzles the Big Bang alone could not.
Alan Guth stumbled on the idea in 1979 while asking a particle physics question: why are there no magnetic monopoles? Grand unified theories, which merge three of nature's forces at extreme temperatures, predict that the hot early universe should have churned out so many of these heavy magnetic charges that they would dominate the cosmos today. Searches have found none. Guth realised that a state called a false vacuum, carrying positive energy, would according to general relativity drive exponential expansion, spreading any monopoles so thin they would be almost impossible to find. Martin Rees teased that preventive medicine always looks perfectly effective against a disease that doesn't exist.
The stronger case came from other riddles. Measurements of the cosmic microwave background show space is flat to within a few percent, and because expansion amplifies any departure from flatness, the young universe must have been tuned to an absurd degree. Inflation smooths that out naturally. It also explains where galaxies came from: plain Big Bang models had no way to seed the lumps gravity needs, but inflation stretches tiny quantum jitters to cosmic size, leaving the density ripples from which structure grew.
The numbers are dizzying. Distances doubled every 10 to the minus 37 seconds, and the episode lasted at least 10 to the minus 35 seconds, though nobody knows exactly how long. When it stopped, the energy of the driving field, dubbed the inflaton, poured into hot particles in a step called reheating, producing a quark soup that kept faint density variations.
Evidence has piled up. The COBE satellite in 1992 found temperature ripples with the nearly scale-invariant pattern inflation predicts, and WMAP added more support, though some scientists remain unconvinced and the underlying particle physics is unknown. Guth, Andrei Linde and Alexei Starobinsky shared the 2014 Kavli Prize for pioneering the theory.
Source: Cosmic inflation
