The Doctor is from earth.
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 his TARDIS , frequently with companions .	Time Lord	Time Lord	Gallifrey	Gallifrey	alien	Extraterrestrials in popular culture	TARDIS	TARDIS	companions	Companion (Doctor Who)
