If you go to Planet X which has 10 times more gravitational pull than Earth, your time would pass slower compared to the rest of us on Earth and once you come back, we all would have aged much more than you would have. And so, you'd have travelled to the future without having aged as much.
But how does time slow down in regions of high gravity?
To understand this, it's relevant to know three facts -
- Speed of light is a universal constant. It does not change, no matter what.
- Strong gravitational regions bend the path of light.
- A beam of light reaches from point A to B in a lower gravity region in the same time as it would in a high gravitational region.
Now let's imagine A and B are two points on Earth. Also, C and D are another two equidistant points on Planet X, whose gravity is 10x of Earth's gravity.
Let's shoot two beams of lights simultaneously from A and C -
Since the gravity on Planet X is higher,
the light beam from C to D (situated on planet X) will bend and take a longer path.
Since the distance travelled by the beam from C to D is longer (refer fact 2 above), it would take this beam more time than the one shot from A to B. But according to fact 3 above, they must reach at the same time.
Using elementary level math, we know that
speed = distance/time
Since speed of light is a constant, for the two beams to reach at the same time, time must slow down for the one travelling through a bent (and longer) path between C to D.
And so, time slows down for you if you're in a region of high gravity compared to someone else present in a region of low gravity.
So another way to time travel to the future? - Hang round a region of high gravity (notably close to a blackhole - just not too close).
By the way, this is how time slowed down for Mathew McConaughey and his crew in the movie Interstellar. The planet they go to 'Miller' was near a blackhole 'Gargantua' which makes there one hour equivalent to 7 years on Earth!