At the Edge of Time: Exploring the Mysteries of Our Universe’s First Seconds (Science Essentials Book 32)

by Dan Hooper

Furthermore, inflation predicts that the primordial variations in density should be approximately—but not perfectly—“scale invariant,” meaning that the pattern of density variations across a given region will look roughly the same as the pattern you would find if you were to zoom in on the image. In this sense, inflation predicts that our universe should be similar to what mathematicians call a fractal. Cosmologists quantify this property using something known as the spectral index of primordial fluctuations, which most theories of inflation predict should be just a little less than 1 (where 1 is the value for a perfectly scale-invariant pattern). The most recent measurements of the cosmic microwave background place the actual value of this quantity at about 0.965—entirely consistent with what inflation had long predicted.