British scientist Stephen Hawking, who turns 70 on Sunday, is regarded as one of the most brilliant physicists since Einstein.<br /><br />His achievements include theories of time and space and the nature of black holes.<br /><br />Another of his great triumphs is how he has defied the medical odds, celebrating his birthday, 47 years after doctors predicted he would die.<br /><br />Al Jazeera's Andrew Potter reports.
