Time travel is, perhaps, the most overused plot device in movies and television. Yet, we are still fascinated by it and still wonder if it’s possible to travel back to the past or into the future. Luckily, scientists have been asking the same question for years, and have some answers.
Whether it’s via flux capacitor or executing a slingshot maneuver around the sun or taking a wormhole, science fiction has come up with all sorts of ways for humans to travel through time.
Unfortunately, time travel is not nearly as easy in real life.
You see, legendary physicist Albert Einstein wondered about it himself in 1905 and came up with an answer by 1915, which I’m sure many scientists would love to ask him about if time travel to the past were possible.
But as it turns out, while travelling back in time is not impossible, it’s beyond our technological and scientific capabilities at the moment.
Einstein published his theory of special relativity in 1915, and it basically states that time does not pass at the same rate for everyone.
So, if a person were to somehow travel near the speed of light for a few years, they would arrive back on Earth and discover that time moved faster for everyone else on the planet, meaning everyone you knew could very well be dead while you only aged a few years during your trip in space.
It’s kind of a scary and cool thing at the same time, and scientists can prove the science is sound.
“Indeed, we can jump forward into the future as much as we want,” Ohio State University astrophysicist Paul Sutter says. “It’s only a matter of going really, really fast. 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. Sci-fi always seem to require complicated contraptions to jump in time, when all you need is a very large rocket.”
Sure, we can shave off a few seconds or several minutes using modern rockets, but in order to travel years into the future without aging very much at all, we would need a ship capable of much faster speeds.
“If one were to depart from the Earth in a spaceship that could accelerate continuously at a comfortable 1 G, one would begin to approach the speed of light relative to the Earth within about a year,” Montana State University professor of physics William Hiscock explained to Scientific American. “As the ship continued to accelerate, it would come ever closer to the speed of light, and its clocks would appear to run at an ever slower rate relative to the Earth. Under such circumstances, a round trip to the center of our galaxy and back to the Earth–a distance of some 60,000 light-years–could be completed in only a little more than 40 years of ship time. Upon arriving back at the Earth, the astronaut would be only 40 years older, while 60,000 years would have passed on the Earth.”
Hiscock went on to point out that while the laws of physics would not prohibit such a trip, current engineering would.
“Such a trip would pose formidable engineering problems: the amount of energy required, even assuming a perfect conversion of mass into energy, is greater than a planetary mass,” he said.
So, travelling to the future is possible, but there would likely not be a way back since travelling back to the past is a far more difficult, if not totally impossible task.
“When it comes to the past,” Sutter said, “the mathematics of general relativity does allow a few strange scenarios where you can end up in your own past. But all of these scenarios end up violating other known physics, like requiring negative mass or infinitely long rotating cylinders.”
In short, Einstein’s theory of relativity is not to blame for not being able to travel back in time, other laws of physics are to blame.
Hiscock concurs, and noted that there is no evidence that any such time travel has occurred or is occurring.
“No experiment or observation has ever indicated that time travel is occurring in our universe,” he said. “Much work has been done by theoretical physicists in the past decade to try to determine whether, in a universe that is initially without time travel, one can build a time machine–in other words, if it is possible to manipulate matter and the geometry of space-time in such a way as to create new paths that circle back in time.”
Of course, an even higher authority on the question of time travel is the late Stephen Hawking, the world renowned physicist who wrote about time travel in his posthumously published final work “Brief Answers to the Big Questions”.
“Rapid space travel and travel back in time can’t be ruled out according to our present understanding,” Hawking wrote. “Einstein showed that it would take an infinite amount of rocket power to accelerate a spaceship to beyond the speed of light.”
But Hawking proposed that wormholes could be the solution to travelling both to the future and back to the past, given certain circumstances.
“So the only way to get from one side of the galaxy to the other in reasonable time would seem to be if we could warp space-time so much that we created a little tube or wormhole,” he wrote.
“This could connect the two sides of the galaxy and act as a shortcut to get from one to the other and back while your friend were still alive. Such wormholes have been seriously suggested as being within the capabilities of a future civilization. But if you can travel from one side of the galaxy to the other in a week or two you could go back through another wormhole and arrive back before you set out. You could even manage to travel back in time with a single wormhole if its two ends were moving relative to each other.”
But Hawking also observed that we haven’t noticed any travelers from the future, so time travel must be relegated to just travelling into the future for now.
“A possible way to reconcile time travel with the fact that we don’t seem to have had any visitors from the future would be to say that such travel can occur only in the future. In this view one would say space-time in our past was fixed because we have observed it and seen that it is not warped enough to allow travel into the past. On the other hand the future is open. So we might be able to warp it enough to allow time travel. But because we can warp space-time only in the future, we wouldn’t be able to travel back to the present time or earlier.”
There you have it. Perhaps, one day, a really intelligent human being will make a groundbreaking discovery or invention that makes two-way time travel possible. Of course, the risks of altering the past to our own peril is a very real possibility that we should think about before travelling to the past. After all, various paradoxes such as the grandfather paradox could accidentally wipe you out of existence. The smallest change could end up having consequences that sweep across time. So, maybe it’s a good thing we can’t travel there yet. The future, on the other hand, is possible for those of us who are willing to live on a spaceship for several years leaving everyone and everything you know behind. But the problem is that we have to leave everything and everyone we know behind, and there’s no turning back the clock to change our mind. Once it’s done, it’s done. And who knows what the future could look like.
But short of a real life Doc Brown from Back to the Future to invent a time machine that can provide instantaneous travel to the past and to the future, we’ll just have to settle for what is currently possible and wait for that moment to arrive. It’s just a matter of time.
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