Time Travel Is Actually Possible But Only One Way, Physicist Explains

There are two ways to travel through time. You can move forward in time, or backward in time. Okay, technically, we are always moving forward in time, so when I speak of time travel, I mean like in fiction. Can travel back and forth through time like Rufus?

Apparently, moving forward in time is actually easier than you think.

Travelling into the future is possible.

WikiMedia | Ferdinand Schmutzer

Brian Greene explained to Business Insider:

"We know how to do it because Einstein showed us the way over a hundred years ago. [...] He showed that if you go out into space and travel near the speed of light, and you turn around, and you come back, your clock will be ticking off time more slowly. So, when you step off it's going to be the future on planet Earth. You will have time traveled into the future."

Traveling forward in time doesn't even have to be as complicated as going into space near the speed of light.


Any time you move faster than those around you, time is slightly slower for you. The effects are just too small to notice.

There are even experiements to prove this phenomenon. A highly accurate atomic clock was synced with an atomic clock placed on a jet. The jet then flew for 14 hours at a high speed. When the plane landed, its clock was nanoseconds slower. This means that the pilot ever so slightly traveled into the future.

You can create a similar time-traveling effect with gravity.

Brian Greene further explained:

"[Einstein] also showed that if you hang out near a nice strong source of gravity — a neutron star, a black hole — and you kind of get right near the edge of that object, time also for you would slow down real slow relative to everybody else. And therefore, when you come back to Earth, for instance, it'll again be far into the future."

We don't need to travel to a neutron star to see this effect either.

Earth is a giant mass. Thus, we should expect that time is slower on the surface of the earth than in orbit. Sure enough, it is. The clocks on satellites, which are 12,550 miles above the surface, run slightly faster than our earth clocks.

Time-travel forward is possible and happens all the time.


But what about going back in time? Things get tricky here. There are various theories, but no proof yet. The most fun theory is wormholes. If wormholes exist, and if we could even travel through them, they might let us travel both ways through time, if they are configured right. That is a lot of "ifs".

If wormholes were combined with the time relativity, you might get time-travel.


Brian Greene explains:

"[...] [Einstein] realized that if you manipulate the openings of a wormhole — put one near a black hole or take one on a high-speed journey — then time of the two openings of this wormhole tunnel will not take off at the same rate, so that you will no longer just go from one location in space to another, if you go through this tunnel — through this wormhole — you'll go from one moment in time to a different moment in time."

We might be able to go forward in time, but we are a long way off from even knowing if travelling backwards through time is possible.


At this point, time-travel looks more one-way, like Fry's trip in Futurama — if you ignore the grandma stuff — than Marty's travels in Back to the Future. However, if all the "ifs" around wormholes pan out, we might get Bill & Ted style time travel. Only time will tell.

h/t: Business Insider