There's no question that time travel is one of the most desired scientific breakthroughs that will hopefully come in the future. Debates have surrounded the topic for many years, and it is starting to look like it may actually be possible ... if it hasn't happened already.
Albert Einstein was one of the first scientists to propose practical methods that could lead to time-traveling capabilities. His theory of special and general relativity shaped how we view space and time. Known as an Einstein-Rosen bridge, a wormhole would be one of the most viable options for time travel, according to Gizmodo.
While there have been no wormholes proven to exist in the universe, theoretically they are a completely feasible physical phenomenon. A wormhole essentially connects two points in time, the present to date or point in the past of time.
Here's the thing, though, on principle alone, wormholes can only take an object or viewer to a point in the past at which it existed. Since the ancient Egyptians didn't invent wormholes, we will never be able to go back to those points. This means that once a wormhole is created, people in the future could, theoretically, travel back in time to that point only, relative to the wormhole used.
Einstein also predicted a physical phenomenon called time dilation, which was proven back in 2014 by a group of scientists in Germany. Their research is published in Nature, here. This theory poses that time passes slower for a clock that is moving than for a clock that is stationary.
Because gravity is a time-dependent force, this would mean that the effects of gravity differ on these two "clocks" as well. A form of a black hole could cause a huge localized dilation in the present, meaning that those nearby could, theoretically, travel into the future. Remember, the theory of "time dilation" is a proven one, not science fiction. This is actually the same principle that caused Astronaut Scott Kelly to age slower than his twin brother on earth.
The proven process of time dilation is the culprit of real-lifetime travel that has already happened. Like the situation with Astronaut Scott Kelly, Cosmonaut Sergei Krikalev has traveled through time to go into the future.
He spent a record 803 days, 9 hours, 39 minutes in space, according to Express.co. When he arrived back on earth, he traveled .02 seconds into the future due to the speed of the ISS relative to earth. While this may not be the time travel you were hoping for, the principles are identical.
Future time travelers would need to harness an extraordinary amount of energy and create a craft that could propel them at the speed of light. Doing so, and traveling through space for relative periods of time, would result in a form of time travel. However, it's a form of time travel that no one can ever come back from.
So, will time travel ever exist? The answer is yes, no and maybe. Yes, time travel already exists in minute provable forms. Maybe, future scientists will be able to take the same principles and apply them on a grander scale. No, that large-scale application is quite likely impossible. Ironically as such, only time will tell if time travel becomes a reality.