How Time Travel Works, Theoretically, In Less Than 1000 Words

By | March 14, 2021

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Simulation of two black holes colliding. (Simulating eXtreme Spacetimes/Wikimedia Commons)

Science-fiction writers and readers have dreamed about traveling through time for hundreds of years, and while it may not be possible to step through a wormhole to the future or flip on a time machine, some researchers believe there are legitimate ways to travel through time. They're just not easy, safe, or even a little practical.

Two Black Holes

Traveling into the future is relatively easy—just wait. Going back in time even a few seconds, however, could require a terrifying sequence of events, like the collision of two black holes. In the vicinity of a black hole, space and time is so distorted that if two of them happened to high-five, a path could be traced around the two spatial anomalies that would take a traveler back ... to the beginning of their journey. According to astrophysicist Neil deGrasse Tyson, "it would be quite a ride for any material swirling in its vicinity," so it's probably not worth it just to go back where you started unless you have a death wish or some kind of Groundhog Day fetish.

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Image of a simulated traversable wormhole that connects the square in front of the physical institutes of University of Tübingen with the sand dunes near Boulogne sur Mer in the north of France. (Philippe E. Hurbain/Wikimedia Commons)


The idea of wormholes pops up time and again in science-fiction. Theoretically, if you slip into a wormhole, you'll exit at a different point in time and space, but that's easier said that done. It's not finding one that's the problem: Scientists believe space is absolutely lousy with the things. It's just that they're a billion-billion times smaller than an electronSomething that small is impossible to study, so while some researchers believe it's possible to enlarge those tiny wormholes to a size that someone could pass through, it's not clear how far one could travel or if anyone would survive the trip.