Hello, I have a homework problem posing the following hypothetical situation Imagine a hypothetical universe in which weak interactions do not exist and only first-generation quarks and leptons are present (i.e. there are no charm, strange, top or bottom quarks, and no muons, muon neutrinos, taus, or tau neutrinos). How would this change BBN (big bang nucleosynthesis)? How would such a Universe be different from our own. Could life exist in this universe? Explain. I know that processes in the early stages of Big Bang Nucleosynthesis would not occur as these are weak interactions such as [itex]\nu_e + n \leftrightarrow e^- + p[/itex] Does this question mean electromagnetic interactions can still occur? Because if so deuterium and therefore helium can still be formed and therefore presumably stars can exist which leads to the heavier elements thus meaning the universe would not be so obviously different. If electromagnetic interactions don't occur then presumably the universe would only contain hydrogen. Not sure if my reasoning is correct here, are there any suggestions of possible outcomes of this type of universe? Thanks in advance.