WILL WE BE ABLE TO CONTROL TIME?

Ever since the publication of the H. G. Wells book we have been dreaming about time travel. Could such a fantastic notion become reality someday?

Imagine you’re a contestant on Who Wants to Be a Millionaire and Jimmy Kimmel asks you: “Who holds the current record for time travel?” Most people would probably wonder if this is a trick question—or a joke. Time travel? The surprising answer is “Gennady Ivanovich Padalka,” the Russian diver, parachutist, and fighter pilot who has traveled into the future. But how can that be?

First of all, it should be noted that, despite the excursion into the future,

The Time Machine,

Mr. Padalka presumably did not feel older after he returned. Background: The Russian pilot and diver is also a cosmonaut—and he happens to hold the world record for the most time spent in space: 878 days in Earth orbit between 1998 and 2015. And since time is a variable that’s influenced by factors such as gravity and speed, it changed during his journey due to the lack of gravity, so to speak—not hypothetically or theoretically, but practically. “When Mr. Padalka came back from his adventures, he found the Earth to be 1/44th of a second to the future of where he expected it to be,” explains Princeton University astrophysicist John Richard Gott III. “He literally traveled into the future.”

The principle behind this isn’t new and can also be tested here on Earth, for example, on a highway: Time will pass more slowly for the occupants of a car than for people in a parking lot. Whether the car is moving at 60 or 80 miles per hour is not relevant. However if the occupants were able to accelerate the car to (almost) the speed of light—i.e., nearly 186,000 miles per second—they would be traveling around 100 years into the future in five days. However, there is a serious obstacle here.

Herbert George Wells invented the time machine in 1895—for his book The Time Machine. It is noteworthy that in the book he defined time as the fourth dimension 10 years before the publication of Einstein’s theory of relativity—a brilliant inspiration. Interestingly it was these theorems that, by the 1920s at the latest, had lent Wells’ notion of a time machine some scientific credibility. Thanks to Einstein’s insight, two things became clear: first, mass and energy are two sides of the same coin; and second, that this “equivalence of mass and energy” influences the curvature of the space-time continuum (which consists of the three dimensions of space and one dimension of time), which in turn influences perception of time in space. In other words: Since Albert Einstein, time suddenly seems to be modelable and controllable. But is that true?

Even today, most theorems about time travel are based on the theory of relativity and various “wormhole theories,” all of which are also based on Einstein’s genius deliberations. The prevailing concept entails the link between a black hole as the entrance and a white hole as the exit of a tunnel, which, according to the famed physicist Nathan Rosen, could serve as a temporal shortcut between two points in space. However, all these concepts currently only work on paper and often not even there. The hurdle that causes most theorems to

fall flat is that we’re not able to achieve the necessary approximation to the speed of light—it’s out of our reach. So to be clear: Time travel is essentially possible at any time—but it is different from what’s portrayed in films and books. In order to be able to travel to the year AD 802,701, as in The Time Machine, one would first have to construct a vehicle (such as a time capsule) that would enable acceleration to nearly the speed of light. Second, one would have to build this vehicle in such a way that it won’t break apart in the process. Apart from these hurdles, which may all yet be surmountable, there is still another problem of the

“unsolvable” variety. Because even if humans possessed the technology at some point and we could fill in the knowledge gaps in the theorems so time travel through a wormhole would be at least theoretically possible, it would still require a journey through a wormhole—and that would be, any way you slice it, almost certainly fatal. Even if not, it would be a one-way trip.

“Time travel in general relativity may allow the universe to be its own mother.” JOHN RICHARD GOTT III, ASTROPHYSICIST