There’s a key line in the new movie "Looper," when Joseph Gordon-Levitt’s character Joe sits down at a diner with a future version of himself, played by Bruce Willis. Understandably, JGL has a lot of questions, while Willis just wants to get down to business. Levitt keeps pushing, and pushing, and pushing, until Willis finally pounds his fist on the table, saying, “If we start getting into this time travel s**t, we’ll be sitting here all day making diagrams with straws!”
It’s a laugh line, and maybe a little bit of a dig at Willis’ last time travel excursion in "Twelve Monkeys". But it also is the complete opposite trajectory from a recent chat I had with Dr. Edward Farhi, of MIT. Farhi, you see, is a theoretical particle physicist, with a specialty in the mechanics of time travel, and how it could – possibly – work.
There’s good news, and bad news on that front. The bad news? Time travel isn’t quite as magical as it is in Looper, and going backwards in time is nearly impossible. The good news? As Farhi explained it, we’re actually all time traveling right now! Hooray!
“In 1905, Einstein showed that time – which could be the way clocks run, the way a chemical reaction goes… Not just the feeling of time, but the actual flow of time, can depend upon the speed of the system,” said Farhi. “That effect is very miniscule if you’re moving slowly, but as you get closer to the speed of light the effects get more dramatic.”
Now of course, most of us are never going to approach the speed of light, but as Farhi explained, if you got on a rocket and started approaching light speed, six months might pass for you, but over a hundred years could potentially have passed back on Earth. That effect, essentially, is time travel: you’ve “skipped into the future,” according to Farhi. “The laws of physics allow that.”
Interestingly, Farhi noted there are things on Earth right now that can travel that fast, like particles in a particle accelerator such as the Large Hadron Collider. So in the lab, scientists can replicate the experience of time travel; except for protons, not human beings. “On the other hand, if you’re going slowly, the effect is less dramatic, but still there,” continued Farhi. One notable example? Every time you use a GPS.
A GPS is located by a GPS satellite through triangulation: i.e., the process of figuring out where you car is, bounced to a satellite, and then your destination is calculated using your speed and location. The catch here is that GPS satellites have clocks that run at a different rate, because they’re in orbit. Because those clocks run at a different rate than Earth clocks, they effectively reproduce the time travel effect. Not quite slingshotting the Enterprise around the Sun, but it is time travel we take advantage of constantly.
There’s also a second way you can affect the flow of time, and that’s with a strong gravitational field. Gravity, in fact, can “warp space and time,” according to Farhi. A clock inside of a strong gravitational field, just like when you approach the speed of light, will run slower than a regular clock. Adding to the effect, if someone outside of a gravitational field was watching someone inside, the person inside would appear to be moving in slow motion, while the person outside would appear to move at super-speed. Additionally, the guy inside the field will age at a slower rate – or at least appear to – versus the person outside the field.
Because of this, Farhi says, “It’s definitely possible to travel to the future, there’s no real question about that. What’s more tricky is going back in time.” There’s paradoxes, of course: if you go backwards, you could affect events so that you were never born, nullifying the time travel to begin with. But even the idea of going forward in time, then “returning” to your original time isn’t possible, because of the same effects. “The fast forwarding part is okay, the going back is more dubious,” continued Farhi.
Just to clarify even further, Farhi added that, “We’re time traveling right now. It’s a minute later than a minute ago. We’re traveling into the future, we can’t stop that. But what’s weird is that you can skip into the future… You can go even a little faster.”
Those hoping to travel backwards in time in order to end up playing in the band at your parent’s high school prom, though, don’t lose hope. Farhi, years ago, found a paper that solved Einstein’s equations… And not only that, described a machine that would allow you to encircle it, and return to your point of origin before you even left. Farhi, intrigued by the paper, turned to his colleagues to find out whether it was possible to build the machine.
Approaching the problem, they started with the idea that – theoretically of course – they had unlimited resources, but still had to follow the laws of physics. “What we discovered that we could build this thing,” said Farhi, “But it required at least half the mass of the universe. That was daunting, but it was only half the story. Another guy looked at the paper, and determined that if you did manage to build this machine, before you could complete the trip… The entire universe would collapse.”
So… You’re saying it’s possible? Well, not really, of course. Farhi added that essentially, the laws of physics are arranged in such a way that they are preventing time travel from ever happening: basically, the universe is built in such a way that if anyone attempts time travel, the universe will self destruct rather than allow it to happen. Pretty hardcore, Universe.
Still speaking theoretically, I noted that it seems like you can travel to the future, because in this theory the future exists as you’re traveling through it. Assuming there was any possibility of past travel, the question becomes: does Past Time exist? Is it still there? And it might be my proudest moment as a journalist that I managed to stump an MIT Professor with this question.
“That’s an interesting question… It certainly exists in the form of memory,” said Farhi. “You can’t go back because it’s not there any more… When there’s a future you can skip into it… I don’t know!”
Point being, the time travel seen in "Looper" isn't possible... But at least you don't have to sit around making diagrams with straws.
Watch a behind-the-scenes chat with the cast and crew of "Looper" about the ins-and-outs of the film's time travel.
"Looper" opens everywhere on September 28th; you can check out more of Dr. Farhi’s work here.