There Are Already People Who Traveled Through Time Among Us

Time travel remains the stuff of science fiction — or is it? Scientists say that some form of time travel is already possible in present day.

It may be not as dramatic as Hollywood depicts, though. For now, time travel remains a one-way trip.

Jumping Forward In Time

Paul Sutter, an astrophysicist at Ohio State University, points out that people already engage in time travel at present, saying that going "back to the future" is already common practice.

"It's only a matter of going really, really fast," Sutter explains in an email to Space.com, citing Albert Einstein's theory of relativity. "The faster you move through space, the slower you move through time. We've been able to measure this with ultra-precise atomic clocks in jet airplanes, and the precision offered by the GPS system needs to take this into account."

As Sutter quips, sci-fi stories always involves huge, complicated machines, but reality only requires a very big rocket.

After all, astronauts, who move faster aboard the International Space Station than regular people on Earth, can already be considered as time travelers. When they're on the ISS, they age just very slightly slower than they do on Earth. NASA's Twin Project proves this when Scott Kelly returned home after a year in space and discovered the gap between him and his twin brother Mark grew bigger by a few milliseconds.

J. Richard Gott, a physicist at Princeton who authored the book Time Travel in Einstein's Universe, tells Popular Mechanics that it's quite simple — theoretically — to send people forward in time.

"If you want to visit Earth in the year 3000, all you have to do is to get on a spaceship and go 99.995 percent the speed of light," he says.

Earth would spin on for a thousand years, but an astronaut making the trip would have their internal clock slowing down due to the speed of their flight.

"[Their] clock will be ticking at 1/100th of the rate of the clocks on Earth. [They] are only going to age about 10 years," Gott points out.

What About The Past?

Of course, the draw of time travel is largely in revisiting the past.

Unfortunately for those who want to go back in time, there's no feasible way of achieving this at the moment. There are a handful of theories on how to achieve it such as going faster than light speed or using wormholes as shortcuts to points in space-time. However, other laws of physics make it inconceivable for humans.

"But all of these scenarios end up violating other known physics, like requiring negative mass or infinitely long rotating cylinders," Sutter explains, adding that physical laws of the universe always "spoil the fun."

For now at least, humanity is bound to this timeline for better or for worse.