Modern thinking is that time did not start with the big bang, and that there was a multiverse even before the big bang. In the inflation theory, and in string theory, there were universes before our big bang, and that big bangs are happening all the time. Universes are formed when bubbles collide or fission into smaller bubles.
Michio KakuIt would take a civilization far more advanced than ours, unbelievably advanced, to begin to manipulate negative energy to create gateways to the past. But if you could obtain large quantities of negative energy-and that's a big "IF" - then you could create a time machine that apparently obeys Einstein's equation and perhaps the laws of quantum theory.
Michio KakuIt is often stated that of all the theories proposed in this century, the silliest is quantum theory. In fact, some say that the only thing that quantum theory has going for it is that it is unquestionably correct.
Michio Kaku