We already know time travel is possible. A fifteen-year study that ended in 2014 settled it once and for all by magnifying time warp, comparing two specially designed clocks using a particle accelerator in Darmstadt, Germany.
The recipe for time travel has been around since Albert Einstein’s 1905 theory of special relativity, which set a 186,000 miles-per-second speed limit for every particle in the universe, specifically light (which always travels at this speed).
We already live in a time warp. Every gorgeous sunset you see was actually 8 minutes and 20 seconds ago.
Polaris, aka the North Star, lies 680 light years from earth, which means you’re looking 680 years into the past when you gaze at it in the night sky. Can we even be sure all of those stars are still there?
Time Dilation Is Real
An even odder phenomenon occurs to objects traveling near the speed of light. It’s called time dilation.
More specifically, the faster an object moves, the slower time passes. Time essentially comes to a standstill upon reaching the speed of light.
So let’s say a 15 year-old interstellar traveler sets off today on a five-year, light-speed journey before returning to Earth.
They’d need some futuristic engineering to stop space debris from shredding them to bits, but it’d be business as usual inside the spaceship.
Their watch would run fine. Or at least that’s the way it would seem to them.
Upon their return to Earth at age 20, their friends would all be senior citizens — or dead.
Your Watch Still Measures Time
If their friends could have somehow seen their watch during the journey, it would have come to a complete standstill from their perspective on Earth.
That’s time dilation. Our traveler is going the speed of light, so their version of time is as slow as it can be, based on the universal speed limit set by special relativity.
Whether or not their watch still works depends on who’s looking at it.