HR: Hugh Riminton
SH: Stephen Hawking
...HR: In that eternity, can things, can matter move backwards and forwards in time?
SH: An elementary particle, like an electron, can move backwards and forwards in time. When it is travelling forwards in time, it appears to be an electron, but when it is going backwards, it is a positron, a particle of the opposite electric charge, which is the anti particle of the electron.
HR: Could a human being ever move backwards or forwards in time?
SH: In the same way, you might imagine that there could be anti people, composed of anti particles, or particles travelling backwards in time. But if you meet your anti self, don’t shake hands. You would both vanish in a great flash of annihilation radiation.
HR: We’ll try to remember that one. ...