The Doctor (Doctor Who)
The Doctor is the title character in the long-running BBC science fiction television programme "Doctor Who". Since the show's inception in 1963, the character has been portrayed by thirteen lead actors. In the programme, "the Doctor" is the alias assumed by a centuries-old alien—a Time Lord from the planet Gallifrey—who travels through space and time in the TARDIS, frequently with companions. The transition to each succeeding actor is explained within the show's narrative through the plot device of "regeneration", a biological function of the Time Lord race that allows a change of cellular structure and appearance with recovery following a potentially fatal injury.
The Science of Doctor Who
The Science of Doctor Who is a televised lecture by physicist Brian Cox discussing the nature of space and time as related to the science fiction series "Doctor Who". Cox covers topics including the nature of black holes, time dilation, time as a dimension in which to travel and the possibilities of alien life. The lecture is held at the Royal Institution's lecture hall and interspersed with small segments of Cox on the TARDIS with the Eleventh Doctor, played by Matt Smith.