Friday, August 14, 2009

Explaining the lack of time travelers from the future

The notion that one version of time travel is more accurate than another might seem ridiculous on its surface, but physicists actually have rather a lot to say about how time travel should work. ...

The many-worlds interpretation provides a fertile basis for time fiction, via the ubiquitous Back to the Future model of alternate histories... Einstein's theory of general relativity­—the branch of physics that might make time travel possible—doesn't take kindly to the idea. Every solution to Einstein's equations involves just a single universe. ...

As a time traveler, you can't visit an era unless there's already a time machine when you get there—an off-ramp. This helps explain why we're not visited by time-traveling tourists from our own future. Futuristic humans don't drop in for dinner because we haven't yet invented time travel.
--Physicist Dave Goldberg, Slate, on time travel rules

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