The bartender said, “We don’t serve time travelers here.” A time traveler walks into a bar.
OK, yes, you’ll almost certainly regret starting this article with such a lame old joke. Most of us, at some point, have wanted to go back in time to fix a mistake or failure. But that’s impossible, right?
Well, not necessarily. Albert Einstein’s theory of general relativity suggests that time travel may actually be possible. We know that matter can bend space-time, and if we bend it enough we may be able to create time loops. Of course, there are many caveats, and researchers have yet to present a working time machine. But that didn’t stop them from exploring the possibilities.
Here are five ways time travel could be possible, from sci-fi classics to surprising new ideas. It also introduces some thorny practical obstacles that need to be overcome.
1. Prepare the galaxy laser ring
The main problem with time travel is that nothing can travel faster than the speed of light, which is 299,792,458 meters per second. This speed limit maintains causation, the idea that the cause must always come before the effect. Thanks to the peculiarities of Einstein’s special theory of relativity and the fact that space and time are inextricably linked, traveling faster than the speed of light will mess it up. If we could travel faster than light, we would travel back in time. But you can’t do that.
The next best thing is to manipulate the fabric of space-time. in…
