PTOLEMY Detector to Hunt for Neutrinos from the Big Bang

The experiment will use cryogenic calorimetry to clinch the first direct detection of the relic particles

Matter in the universe — Matter as we know it — protons, neutrons, electrons and other subatomic particles — makes up only about 4 percent of the universe. Dark matter and dark energy make up the remaining 96 percent.

One second after the Big Bang, an unfathomable number of neutrinos were liberated from the surrounding chaos and started traveling through the universe at nearly the speed of light. Cosmologists believe a person is bombarded with something on the order of a quadrillion of these ‘relic neutrinos’ every second, dwarfing, unbelievably, the number of neutrinos that come from other relatively nearby sources, such as nuclear fusion in the sun or radioactive decay.

“You hear this, and you’re driven to ask whether it’s really true,” says Princeton University physics professor Christopher Tully. “How can we know it’s true?”