If the total energy of the universe must always remain zero, and it costs energy to create a body, how can a whole universe be created from nothing?
Stephen HawkingTime travel was once considered scientific heresy, and I used to avoid talking about it for fear of being labelled a 'crank.'
Stephen HawkingGravity is so strong that space is bent round onto itself, making it rather like the surface of the earth. If one keeps traveling in a certain direction on the surface of the earth, one never comes up against an impassable barrier or falls over the edge, but eventually comes back to where one started.
Stephen Hawking