A neutrino is a neutral particle with very low mass, possibly zero. It has spin 1/2 and so is a fermion. It does not interact with the strong force or the electromagnetic force, but does interact with the weak force (and with gravity if it turns out to have mass). The cosmic neutrino background (CNB) is the universe’s background particle radiation composed of neutrinos. Like the cosmic microwave background radiation (CMB), the CNB is a relic of the big bang, and while the CMB dates from when the universe was 380,000 years old, the CNB decoupled from matter when the universe was 2 seconds old. It is estimated that the CNB has a temperature of 1.9 kelvins or lower. Neutrinos are notoriously difficult to detect, and because the cosmic neutrinos are so cold, the CNB might never be observed directly.
A Nasa space probe measuring the oldest light in the Universe has found that cosmic neutrinos made up 10% of matter shortly after the Big Bang.
Five years of study data also shows that the first stars took over half a billion years to light up the Universe.
WMAP launched in 2001 on a mission to measure remnants of light left over from the Big Bang.
Scientists say it is collecting a “treasure trove” of information about the Universe’s age, make-up and fate.