Ask Ethan: Can we see the cosmic neutrino background?

One of the hardest concepts to wrap our head around is that of the hot Big Bang: the notion that our Universe began 13.8 billion years ago from an extraordinarily hot, dense, uniform, and rapidly expanding state. Initially, all known species of particles and antiparticles confirmed to exist, along with possibly others that we only speculate about at present, as there was more than enough energy to spontaneously create particle-antiparticle pairs of all types via Einstein’s famous E = mc². Since that early time, the Universe has expanded and cooled substantially, eventually giving rise to atomic nuclei, stable atoms, along with stars, galaxies, and cosmic structure on the largest scales. But it isn’t just atoms and other structures composed of protons, neutrons, and electrons left over from that early epoch, but also cosmic backgrounds of far more numerous particles. While the relic background of photons, the cosmic microwave background (CMB), is by far the most famous leftover cosmic fossil, there should be another one composed of neutrinos and antineutrinos: the cosmic neutrino background. Reader Daniel S. Gelu wants to know about it, writing in to ask: <a href="https://medium.com/starts-with-a-bang/ask-ethan-can-we-see-the-cosmic-neutrino-background-48dadad0a81a">Read More</a>