What Was It Like When We Lost The Last Of Our Antimatter?
“The Cosmic Microwave Background’s temperature was first measured to this precision back in 1992, with the first data release of NASA’s COBE satellite. But the neutrino background imprints itself in a very subtle way, and wasn’t detected until 2015. When it was finally discovered, the scientists who did the work found a phase shift in the Cosmic Microwave Background’s fluctuations that enabled them to determine, if neutrinos were massless today, how much energy they’d have at this early time.
Their results? The Cosmic Neutrino Background had an equivalent temperature of 1.96 ± 0.02 K, in perfect agreement with the Big Bang’s predictions.”
Throughout the very early Universe, space was filled with matter and antimatter, which spontaneously self-create from pure Energy via Einstein’s famous E = mc^2. However, as the Universe cools and expands, less energy becomes available to make new particles and antiparticles. Quarks, muons, taus, baryons, mesons, and gauge bosons all are gone by time the Universe is just 25 microseconds old. But positrons, the counterpart of antielectrons, remain until the Universe is a full 3 seconds old! Their existence leads to a crazy prediction: that there should be a cosmic neutrino background at a different temperature from the cosmic microwave background: 1.95 K instead of 2.73 K.
We have verified this, and hence, one of the Big Bang’s craziest predictions, with data collected 13.8 billion years onward! Come learn what it was like when the Universe lost the last of its antimatter.