Is Time Travel Possible? NASA, Einstein & Live Science say yes!

From The Twilight Zone to Rick & Morty, the idea of traveling through space to the past or future has been around for ages. But as video telephones, self-driving cars and other sci-fi dreams have turned reality, it's theorized that time travel may be possible too. Here's how:

Nasa theorized that time travel is possible with an experiment on twin brothers, Astronaut Scott Kelly aged milliseconds less than his twin brother who stayed on Earth. Clocks prove the same phenomenon - time moves more slowly closer to Earth and faster further away.

This is a key part of Einstein's Theory of Relativity: Time is not a fixed and stable thing, but it is an illusion relative to an observer. The only stable unit is the speed of light. That is always the same no matter what.

Einstein theorized that the closer one travels to the speed of light, the slower they experience time, aging, etc.

The Theory of General Relativity says if someone could travel at the speed of light or faster, they could theoretically age far slower than those on Earth. Depending on the speed, it could mean traveling for a year and returning to Earth years later. AKA future time travel!

Going back in time is a bit more complicated, but still potentially plausible. Wormholes are a theoretical solution as to how General Relativity could allow for this possibility. These are essentially tunnels or shortcuts between different points in time and space.

Alternate theories of how time travel could be possible include the Tipler Cylinder which would take matter 10x the sun's mass, rolled into a long cylinder and spinning it a few billion revolutions per minute. A spaceship precisely spiraling nearby could travel back in time.

Another theory is a proposed model for curved space-time, like a "time donut". It's a machine that could "warp space and enable future generations to return to visit our time" - according to Theoretical Physicist Amos Ori.

The largest hurdle to all theories of time travel is gravity. As of yet, there has been no solution as to how a human could survive the gravitational pull required by any of of these methods in order to travel through space-time.

Bottom line: Einstein theorized, and numerous physicists since have continued to expand on the idea, that time travel could be possible by manipulating the fact that time is relative to the observer. However, so far we've only been able to manipulate time-space by milliseconds.