Fine Structure

Rules For Time Travel

I admit to discussing some of the finer points of fictionalized time travel after seeing the new Star Trek film the other day (and most importantly, how it compares to time travel in Lost), but Sean Carroll wins the day by writing up the rules for time travel. Here's one way to think about time travel, via rule #3:

Traveling through time is just like traveling through space: you move along a certain path, which (we are presuming) the universe has helpfully arranged so that your travels bring you to an earlier moment in time. But a time machine wouldn't look like a booth with spinning wheels that dematerializes now and rematerializes some other time; it would look like a rocket ship. Or possibly a DeLorean, in the unlikely event that your closed timelike curve started right here on Earth and never left the road.

This gets into all sorts of interesting questions like "what would a path that allows time travel in the universe look like?" and "why does Sean Carroll think you can't retrofit a DeLorean for space travel?" His bio on twitter is appropriate: Time Lord. ]