One way to achieve time travel into the future would be travelling at the speed of light in space, as first theorised by Albert Einstein.
The accepted theory is that one would have to build a space ship that can travel at the speed of light, and head out into space.
Theoretical physicist and string theorist Brian Greene, of Columbia University, said: “You can build a spaceship, go out into space [and travel] near the speed of light, turn around and come back.
“Imagine you go out for six months and you turn around and you come back for six months.”
While you are travelling at the speed of light, time stays slow relative to the people who are standing still back on Earth.
As a result, you would be going fast while your clock would still be going slow.
Prof Greene: “When you step out of your ship, you’re one year older but Earth has gone through many, many years.
“It can have gone through 10,000, 100,000 or a million years depending on how close to the speed of light you traveled.”
However, the only problem is that a machine travelling at such speed would require an “unimaginable” amount of energy, while the stress from the centrifugal force on the body would likely prove fatal.
One way to travel in time is to hang out near the edge of a black hole
But there is another feasible way to travel though time, and once again it involves going into outer space.
Einstein also theorised that if you were to situate yourself on the edge of a black hole, time would pass more slowly.
Einstein also theorised that if you were to situate yourself on the edge of a black hole, time would pass more slowly.
Prof Greene explains in his Big Think video: “You hang out [next to a black hole] for a while, you come back, get out of your ship and it will be any number of years into the future, whatever you want all depending on how close you got to the edge of the black hole and how long you hung out there.
“That is time travel to the future.”
But time travel has already happened.
Cosmonaut Sergei Krikalev has already travelled through time
Serial ISS resident Sergei Krikalev holds the record for the longest amount of time spent in space with 803 days, 9 hours, 39 minutes under his belt.
The ISS travels at around 7.66 km/s when orbiting around Earth, and due to the high speed and length of time which he spent in space, the cosmonaut actually arrived back in Earth 0.02 seconds in the future thanks to a process known as time dilation.