'Cosmos' Episode 4 Preview: 'A Sky Full Of Ghosts' Trailers Highlight Time, Light, Gravity And Patrick Stewart

"Cosmos" returns to Fox and in the fourth episode, "A Sky Full of Ghosts," Neil deGrasse Tyson explores how our view of the universe is shaped by light, time and gravity. For its heroes of science segment, Sir Patrick Stewart ("Star Trek") will be the voice of astronomer William Herschel.