Time travel is the process by which a person or object moves itself through the timestream through unconventional means. This process can be achieved through an artificial construct that allows one to translocate their corporeal form backward or forward through time, usually referred to as a time machine. Some may develop a psychokinetic ability to transpose their consciousness through the timestream while their physical body remains at its origin point. Time travel has been featured in a multitude of science fiction stories, novels, films and television programs such as Doctor Who, Timecop, Quantum Leap and Time Trax, which deals expressly with the subject of time travel, but has also been presented in other sci-fi programs like Farscape, Star Trek, Star Trek: The Next Generation, Star Trek: Deep Space Nine, Star Trek: Voyager and Star Trek: Enterprise.
- "An Unearthly Child": The First Doctor brings Susan Foreman, Ian Chesterston and Barbara Wright back in time 100,000 years to the Paleolithic era.