These relic neutrinos formed in the first second after the Big Bang. Almost massless and rarely interacting with matter, they permeate the cosmos. Detecting them is extraordinarily difficult, but they carry information about the early universe. Their behavior helps cosmologists test Big Bang models and particle physics. Neutrino background is the universe’s oldest known radiation after the cosmic microwave background. They are silent messengers of the first moments of creation.
Neutrinos matter because they reveal conditions of the universe’s first second.
They also help refine models of particle interactions and cosmic evolution.
Relic neutrinos from the Big Bang pass through your body constantly, unnoticed.
University of Washington [phys.washington.edu]