Time travel happens every day. You just don't realise it because it happens on such a minuscule scale.
No, I've not finally lost the plot, time travel into the future is possible. Let's look at an example. Ironman is walking along a (cross-franchise) rocket. He whizzes past a Stormtrooper.
If Ironman is walking a 2 mph, he thinks his speed is 2 mph. But the Stormtrooper sees his speed as 2mph PLUS the speed of the rocket.
This concept doesn't just work for speed, it also works for time. Basically, the amount of time that passes between two events depends on your point of reference.
When you move really fast and approach the speed of light, the slower time passes for you. It's an effect called time dilation.
Essentially, the faster you move through space, the slower you move through time.
So, if you went on a spaceship travelling at close to the speed of light, then came back to Earth - you'd be returning to a future Earth where time has passed faster on the planet than in your spaceship.
Gravity also messes with the passage of time. The greater the gravity, the greater your speed and (therefore) the slower you'll move in time.
If, for example, you were in a spaceship and decided to go on a day trip to a black hole (which massively warps the fabric of space-time) then time would pass quicker, again, for you compared to someone further away from the black hole.
Can you travel back in time?
Theoretically, yes. But you'd need something called a wormhole, which essentially acts as a bridge through time and space to connect two distant points with a shortcut.
It's still a topic of great debate in the scientific community, but one of the major constraints is that you need to create a wormhole to travel in time. So, you can only travel forwards in time - because even if we created a wormhole capable of carrying humans now, no one has created one in the past for us to travel back to.
Oh, and you'd need to be travelling a near to the speed of light for all of this to work.
Confused? Don't worry - I'll look more into wormholes next week!
If you're not convinced about time dilation, then this experiment finally proved the phenomenon a few years ago. And did you know that the clocks on the International Space Station (hurtling around the Earth at more than 17,000 mph) also tick a little bit more slowly than the clocks on Earth?
The premise of time travel is also deeply rooted in two of Einstein's theories that I've covered in previous Sunday Science posts: General Relativity and Special Relativity.
If you want to read more about wormholes and time travel into the future, this is a great article.
Finally, Brian Cox explained time travel as part of a special Science of Doctor Who lecture a few years ago. You can check out the video clips here.
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