Entropic Time Machine (ETM) is a set of technologies that allows one to travel through time, specifically to any point in the past. It is called “entropic” because its method sidesteps the second law of thermodynamics, which makes it highly improbable for entropy to decrease, thus making time travel to the past nearly or fully impossible.

Instead, the ETM finds an identical copy of the timeline and inserts the time traveler into it, this creating an Alternate Timeline.