Ethan Siegel discusses neutrinos, the one last Big Bang prediction that has yet to be verified. via Medium:
The mass-and-energy of these neutrinos tell us that they’ve fallen into the large-and-small-scale structures in the Universe, including in our own galaxy. They tell us that they’re a small percentage of the dark matter — between about 0.5%-and-1.4% of it — but cannot be all of it. There’s about as much mass in neutrinos as there is mass in the form of stars currently burning through their fuel today. Not a lot, but still interesting!
But what’s maybe most amazing about these neutrinos is that we have no practical idea about how we could experimentally detect them!
We can detect neutrinos, but only neutrinos with about a billion times the energy of these cosmic relics. Because of how quickly (exponentially) the cross-section falls off, we really have no hope for how to detect something with such a small signature; all of the neutrino detectors we’ve built and successfully implemented rely on ultra-high-energy neutrinos.