What is Neutrinos.................
Answers
Answer:
Neutrinos are extremely weakly interacting particles, produced for example in radioactive decay. There is now significant experimental evidence that they possess a non-zero rest mass, but it is unclear whether this mass might be large enough to have cosmological effects, and it remains a working assumption in cosmology to treat them as effectively massless. I will adopt that assumption for the main body ofthis book, and in that case they, like photons, are always relativistic. The combination of photons and neutrinos makes up the relativistic material in our Universe. Confusingly, sometimes the term 'radiation' is used to refer to all the relativistic material.
There are three types of neutrino, the electron neutrino, muon neutrino and tau neutrino, and if they are indeed all massless they should all exist in our Universe. Unfortunately, their interactions are so weak that for now there is no hope of detecting cosmological neutrinos directly. Originally their presence was inferred on purely theoretical grounds, though we will see that the existence of the cosmic neutrino background may be inferred indirectly by some cosmological observations.
Answer:
A neutrino is a subatomic particle that is very similar to an electron, but has no electrical charge and a very small mass, which might even be zero. Neutrinos are one of the most abundant particles in the universe.