Technologies in the Film
People have long fantasized about traveling through time. In Back to the Future II, Marty and Doc Brown, using the time-traveling DeLorean, travel from 1985 to thirty years into the future and back within the same day, but people today wonder if time travel will ever be possible in the real world.
In truth, physicists have proven that time travel indeed is possible, but only forward in time. Einstein's theory of relativity showed the world that forward time travel is possible if a body is moving fast enough to approach the speed of light -- about 670 million miles per hour. Einstein showed that time actually warps in order to accommodate fast-moving bodies . As a result, if two twins were born on the Earth and one of them left the Earth traveling close to the speed of light and then came back, the twin on Earth would have aged more even though neither twin would have felt time changing at all . Time also changes speed in the presence of gravitational fields, so time actually travels faster on the International Space Station than on Earth . These two effects together are called time dilation .
Physically, you are already traveling forwards through time at what feels like a constant rate, so another method of traveling to the future is cryonics -- freezing your body just before you die in the hopes that one day technology will be advanced enough to wake you up and subsequently grant you immortality. However, although several cryonics services exist today, many different issues question the viability of this method, such as brain tissue damage from cold temperatures .
As of yet, time travel backwards in time has not yet been proven to exist, and some physicists claim to have proven that time travel backwards is not possible in our universe, but their work has yet to be widely accepted as fact . Of course, many complications arise as a result of traveling back in time, such as the grandfather paradox -- the paradox that would arise if you went back in time and killed your own grandfather, therefore preventing yourself from existing to kill your own grandfather in the first place . Stephen Hawking, an esteemed physicist and cosmologist, threw a party in 2012 for time travelers from the future . Unfortunately, no one attended, which creates more doubts that backwards time travel will ever be invented in the future, unfortunately.
Finally, the computing involved
 NASA Spaceplace, Is Time Travel Possible?
 John Fuller, Does Time Change Speed?
 Andrew Tarantola, Why Freezing Yourself Is a Terrible Way to Achieve Immortality
 Sara Goudarzi, You Can't Travel Back in Time, Scientists Say
 Kevin Bonsor and Robert Lamb, How Time Travel Works
 Michael Rundle, Stephen Hawking: 'I Held A Party For Time-Travellers... But None Came'