Inflation not only explains the uniformity that we see in the cosmic background radiation, but it also explains the statistical properties of the very faint nonuniformities that have been observed with instruments so sensitive that they can measure minute variations of less than 1/1000 of a percent.

       While inflation must be tested and judged on the basis of what it says about observable features of the universe, curiosity leads us to ask what inflation says about the universe as a whole. The answer is bizarre.

       The gravitational repulsion of the false vacuum that is believed to have driven inflation is so strong that it would have launched a period of incredibly rapid expansion. The region would have doubled in size in about 10^-37 (i.e., a decimal point followed by 36 zeroes and a 1) second. In the next 10^-37 second it would have doubled again, and it would have kept doubling every 10^-37 seconds for as long as the false vacuum survived. The false vacuum is unstable, however, so at some point it “decayed,” converting its energy to a hot soup of ordinary particles. From this point onward the scenario would coincide with the standard hot big bang picture. The dramatic expansion, however, strongly suggests that the universe would be far larger than one would have otherwise imagined, so the observed part of the universe would be merely a speck in a much larger space.