Actually, if light had mass, the whole universe as we know it would be completely different. Even if it was a tiny, tiny mass, due to the immense speeds it travels, the kinetic energy would be huge! Light being massless is what allows it to travel at 'c', the speed …

Ok, so there's actually a quantum theory about this – the Many-Worlds Interpretation proposes that all possible alternate histories and futures are real, just in separate 'branches'. It's not exactly mainstream since there's no way to prove it (yet?), but it's a legit scientific idea. Just imagine, with every tiny …