4 ms·

> There is no theory yet for the origin of Big Bang There are many.

• adrian_b 5y ago
  None of them can explain anything besides what is already explained without them. The Big Bang theory that is useful starts with matter at very high temperature and density, but otherwise not different from the matter that we know. That happens at some uncertain time interval after the beginning of Big Bang. We may try to extrapolate towards time 0 and increasing temperatures and densities, but that reaches soon values of temperature and pressure high enough that we do not really know how matter behaves in those conditions and it does not matter anyway because it does not influence what happens later. For the later evolution, it is enough to start the modeling of Big Bang from the moment when the temperature became low enough, e.g. of some tens of MeV, i.e. when matter was too hot for nuclei and atoms to exist, but cold enough so that it consisted of a plasma composed of protons, neutrons, electrons, positrons, photons and neutrinos, with only negligible quantities of heavier particles. For the time 0 there is no theory that can predict anything quantitative.