Can We Travel through Time to the Past?

Have you ever wished you could go back in time to right a wrong, to make a different decision or even completely alter the course of history? It's a favorite plot device in science fiction and fantasy stories, but could it happen? Is it even possible? Let's look at some possible ways that theoretically could work.

TRAVELING INTO THE PAST
It turns out that we time travel all the time. We move from the past to the present.

And, as we experience our lives here on Earth, we are constantly moving into the future. Unfortunately, we have little control over how quickly that time passes and we can't seem to stop it and continue to live.

But what about traveling into the past? According to Einstein's theory of relativity, time only flows in one direction: forward. If time flowed the other way, we would remember the future instead of the past. So, on the face of it, traveling into the past seems to be a violation of the laws of physics. But not so fast. There are theoretical considerations to take into account if you want to build a time machine that goes back to the past.

BLACK HOLES AND WORMHOLES
The idea of building a time machine, like those often depicted in science fiction films, is likely the stuff of dreams. Unlike the traveler in H.G. Wells's Time Machine, no one has figured out how to build a special carriage that goes from now to yesterday.

However, one could possibly harness the power of a black hole to venture through time and space.

According to general relativity, a rotating black hole could create a wormhole — a theoretical link between two points of space-time, or perhaps even two points in different universes. However, there's a problem with black holes.

They've long been thought to be unstable and therefore un-traversable. However, recent advances in physics theory have shown that these constructs could, in fact, provide a means of traveling through time. Unfortunately, we have almost no idea what to expect by doing so.

Theoretical physics is still trying to predict what would happen inside the wormhole, assuming one could even approach such a place. More to the point, there's no current engineering solution that would allow us to build a craft that would let make that trip safely. Right now, as it stands, once you enter the black hole, you're crushed by incredible gravity and are made one with the singularity at its heart.

But, if it were possible to pass through a wormhole, it would probably be a lot like Alice falling through the rabbit hole. Who knows what we would find on the other side? Or in what time frame?