The bartender says, “We don’t serve time travelers here.” A time traveler walks into a bar.
Okay, yes, I’m almost certainly going to regret starting this article with such an old joke. At some point, most of us have been able to travel back in time to fix bugs or errors. But it’s impossible, isn’t it?
Well, not necessarily. Albert Einstein’s general theory of relativity suggests this time travel may be possible. We know that matter can bend spacetime, and if you bend it enough, you might be able to create a time loop. Lots of caveats, of course, and researchers have yet to announce a working time machine. But that hasn’t put them off exploring the possibilities.
Here are five ways that time travel could be feasible, from sci-fi basics to surprising new ideas, as well as some grim practical hurdles we’d have to overcome.
1. Ring a galactic ring laser
The main problem with time travel is that nothing can travel faster than the speed of light, which travels at 299,792,458 meters per second. This speed limit preserves causality, the idea that cause must always come before effect. Traveling faster than the speed of light would mess that up, thanks to Einstein’s quirks of special relativity and the fact that space and time are inextricably linked. If we went faster than light, we would travel back in time. But we can’t.
The next best thing, then, is to manipulate the fabric of space-time. in the year…
