Hawking says the universe had no clear "bang." You can wind back the clock to the edges of those first moments of existence, but asking what came before would be like asking why you can keep walking north when you get to the North Pole. Time, as we define it, loses its meaning as the universe shrinks down.

It never quite narrows to a single point. But no one has proved physics works like that—yet.

Hawking proposes a no boundary condition version of space-time. As you approach the beginning space-time is replaced with imaginary time.

In theoretical physics, the Hartle–Hawking state, named after James Hartle and Stephen Hawking, is a proposal concerning the state of the universe prior to the Planck epoch.