“When you see how fragile and delicate life can be, all else fades into the background.” –Jenna Morasca
The hot Big Bang — proposed seventy years ago — is a tremendous success story. Predicated on the assumption that the Universe was hotter, denser, more uniform and expanding faster in the past, it’s allowed us to predict the rate of cosmic expansion over distance and time, the primeval abundances of the light elements, the formation and evolution of large-scale-structure, and the existence and properties of the cosmic microwave background: the leftover photon glow from the Big Bang.
All these predictions have been borne out, but there’s one more prediction that had yet to be tested: the existence and properties of a cosmic neutrino background. A new technique taking advantage of data from the Planck satellite has just detected the cosmic neutrino background definitively and in a new way. After seventy years of searching, we’ve finally confirmed the greatest prediction of all: the cosmic neutrino background’s existence and temperature!