I didn’t know what was his name, but I knew him very well from the various popular science movies that he’s been in
he’s an American theoretical physicist, a very interesting character, explains things in a simple language
now he’s a professor in theoretical physics at City College of New York, hosts two radio programs, writes books and of course, does movies 
you can see some of his work at YouTube (just click the link)
anyway, I think I should mention him because he deserves it
here’s his Wikipedia page