It is a plot device of countless science-fiction tales; through some means or another characters are whisked away into the future. Sometimes it's intentional, others it's due to a series of unexplainable circumstances. But is it possible? Could we ever travel into the future?
The Nature of Time
Whether you realize it or not, you are always traveling into the future. It is the nature of space-time. The flow of time, as we currently understand the laws of physics, always flows into the future.
This is why we remember the past (instead of "remembering" the future). And it is also why we don't know what is why the future is unpredictable, because it hasn't happened yet.
So as we plod along in our everyday lives we experience time moving forward all around us. But what if we desired to speed up the process, to peer further into the future? To experience events more quickly than those around us? Is that possible?
Traveling into the Future
It may also surprise you to learn that it is possible to speed up the passage of time, at least in small quantities. And there are people alive that have experienced such a phenomenon.
According to Einstein's theory of special relativity, the passage of time is relative to an objects speed. That is, the more quickly an object moves, the more slowly time passes compared to an observer traveling at a slower pace.
The classic example of this is the twin-paradox. In short, a set of twins, aged 20 years are living on Earth. One of the twins takes off on a spaceship on a 5 year journey traveling at nearly the speed of light.
When he returns to Earth he is now 25 years old. However, his brother, who stayed behind, is now 95 years old. This is because the passage of time was slowed down for the brother on the spaceship as his speed approached the speed of light.
When he returns to Earth, he has effectively traveled into the future.
Using Gravity as a Means of Time Travel
In much the same way that traveling at speeds close to the speed of light can alter the flow of time, intense gravitational fields can have the same effect.
Gravity effectively is a warping of space-time, and therefore affects not only space, but time as well. The result is that time passes more slowly for an observer as they enter a massive object's gravitational well.
Astronauts, traveling on the space shuttle or International Space Station experience a combination of these effects, though on a smaller scale. Since they are traveling quite quickly and orbiting around Earth (a massive body with significant gravity), time slows down for them compared to those back on Earth. The difference is small, much much less than a second over the course of their time in space. But it is a measurable difference nonetheless.
Could We Ever Travel into the Future?
We've seen how we can slow the passage of time for human passengers traveling near the speed of light and near intense gravitational wells. But these effects are small.
Until we can figure out a way to approach the speed of light (and warp drive doesn't count, not that we know how to do that either at this point), or travel near black holes (or travel to black holes for that matter) without falling in, we won't be able to experience time travel any significant distance into the future.