Topic summary
Time portal
Extracted from the Wikipedia article Time travel in fiction.
Time portal
A time portal or a time gate is a doorway in time, employed in various fiction genres, especially science fiction and fantasy, to transport characters to the past or future. They differ from time machines in being a permanent or semi-permanent fixture, often linking specific points in time. An influential example of such a work is the short story, "By His Bootstraps", by Robert A. Heinlein, which features a time gate built by aliens and plays with some of the inherent paradoxes that would be caused by time travel.