Under the Radar

The Science of 'Looper'


Looper isn't one of those movies where you turn your mind off and sit blankly through a couple of hours of explosions and chase scenes. You've got to pay attention to keep up with the plot and you're going to be thinking about what you saw for days (or weeks or months or maybe even years) to come.

Looper is set 30 years in the future. Joseph Gordon-Levitt and Bruce Willis star as younger and older versions of the same looper, a hitman whose job it is to knock off victims sent back through a time-travel portal. Jeff Daniels plays a crime boss from the future who pays off the killers and runs the show. Apparently, his boss (who lives 30 years even later in the future) is tying up loose ends and sending back older versions of his loopers so their younger versions can kill them and "close the loop."

The screenplay was written by director Rian Johnson and it plays like an homage to Philip K. Dick that's a lot truer to Dick's cracked vision than most of the movies based on his books. Johnson doesn't think the audience is dumb and he's asking us to expend a little brain power to keep up with his movie.

Since time travel is treated as a serious topic in the movie, we got the people over at Zoomwerks to introduce us to a physicist who actually understands the subject. Dr. Ronald Mallett is a professor of physics at the University of Connecticut whose own work investigates the possibility of time travel. He was kind enough to explain things in a way that made sense.


Mallett's book Time Traveler: A Scientist's Personal Mission to Make Time Travel a Reality is a memoir that details how his own life influenced his interest in time travel and the research he's done to prove it's possible. So now we're going to get into it. Even though we were just looking for a few interesting quotes, his explanations are so good that we're going to run with it and let him give us all a physics lesson. Dr. Mallett explains how Einstein's theories prove time travel is possible, the grandfather paradox and how sometimes we need a crisis to inspire us to invest the money we need to create scientific breakthroughs.

Tell us about your background and your interest in time travel.

My interest in time travel is actually due to a personal tragedy that occurred when I was ten years old. I was the oldest of four children and I grew up in the Bronx, NY. My father, Boyd Mallett, was a TV repairman in the Bronx and he was really the center of my life. For me, the sun rose and set on him. He looked like he was very healthy but we didn't really realize that he had a weak heart. He died of a massive heart attack when he was only 33 years old. I was devastated. It crushed my world and I went from being a happy kid to a rather depressed kid. My father left me a lot of gifts and one of them was a love for reading and I love reading science fiction.

About a year after his death, when I was 11, I came across a book that really changed my life. It was HG Wells' classic The Time Machine and that turned my life around completely because it gave me a goal and a dream. If I could build a time machine, then I could go back in the past and see my father again and maybe save his life. So that became my goal. I didn't tell people about it because they were already worried about me. Even at that age, I thought there might not be good consequences.

I discovered the second most important book of my life when I was 12 or 13 and came across a paperback, a popular-level book about Einstein. It was called The Universe and Dr. Einstein. In that book, it stated that Einstein said that time was not something that was just fixed, that time could actually be altered and, for me, at that age, the idea that time could be altered meant that time travel might be possible. Einstein became my second obsession. I wanted to learn about that. That was the beginning of my journey, that was how things started out for me.

Bruce says, "Pay attention, you might learn something."

Time travel to the future and the past is possible based on Einstein's theories of relativity. Current experiments have shown that time travel to the future has been achieved. We have recent theoretical work that's demonstrated the possibility of time travel to the past.

I'll divide Einstein's theories of relativity up into two parts. He developed two theories. One was his Special Theory of Relativity, which he developed in 1905, and the other was the General Theory of Relativity, developed in 1915.

In a nutshell, the Special Theory of Relativity is about how time is effected by speed. Einstein  developed a theoretical mathematical model showing that time for moving clocks slows down at a high speed. The faster an object moves the more time slows down for that object. This has actually been demonstrated in a number of different ways.

One of the things that people may not realize is that, whenever scientists use particle accelerators like the large Hadron Collider, they speed up subatomic particles. Some of these particles live only for a very, very short period of time, a mere fraction of a second before they disintegrate. What they find is that when they speed these particles up, they can get these particles to live ten to twenty times longer than they normally would, which is exactly what Einstein predicted that, at high speeds, a clock would actually slow down. This means that these particles are actually traveling into the future.

You can translate it into human terms: our heart rates, our metabolisms: these are clocks that would be affected by motion, too. If we were traveling fast enough, this would mean that are heart rate and our metabolism would slow down and we'd age less than everyone else who would age at the normal rate. If we were traveling fast enough, we would arrive in the future sooner than anyone else.

When you see time travel movies about going into the future, the person going into the future only ages a little bit and everyone else ages decades, so when the person arrives in the future, they're maybe only a few hours older and everyone else is decades older. That's actually what they're seeing in the experiments in the large Hadron Collider. That's what these subatomic particles are doing, they're actually traveling to the future.

We've also seen the effect on a large scale. Not many people may know this, but in 1971 the Naval Observatory did an experiment with two atomic clocks. An atomic clock is the most precise time-keeping mechanism we have. One of these atomic clocks is kept at rest at the Naval Observatory. The other atomic clock was put on an ordinary passenger jet and flown around the world at the speed of sound. When they brought the plane back, they found that the clock on the passenger jet had actually slowed down, had actually lost time. This means that it had traveled fractions of a second into the future.

The reason this experiment didn't have a bigger effect was that, even though the plane was traveling at the speed of sound, that's slow compared to the speed of light. As you probably know, speed of sound is sometimes measured in terms of mach numbers. Mach 1 is one time the speed of sound, Mach 2 is two times the speed of sound and so on. We have passenger jets that can do mach 1. We have fighter jets that can do Mach 2. We have stealth fighters that can do Mach 3.

If you translate the speed of light into the speed of sound, into Mach numbers, the speed of light goes 186,000 miles per second. If you translate that into the speed of sound, it turns out that the speed of light is moving at Mach one million.

Right about now, your mind should be starting to get blown.

As far as light is concerned, sound is practically standing still. NASA is looked at advanced propulsion rockets and, when we have rockets that can go close to the speed of light, we'll see this effect not only just in terms of fractions of a second but in terms of years and decades. That means that an astronaut going out to space maybe for them only a few years will have passed but when they come back if they've been traveling close to the speed of light they could find that decades have passed here on the Earth. If they had families before they left, they could actually come back and find that they're younger than their children.

This is real. We've already actually seen the baby steps of this in the laboratory with particle accelerators and experiments like the one done at the Naval Observatory. So, with travel to the future, we've already achieved it in just baby steps. Once we can go fast enough, it'll be more dramatic.

The thing we haven't seen yet is time travel to the past and, from the standpoint of Einstein's Special Theory of Relativity, that can't happen. No matter how fast you go, you can't go back into the past because the speed of light acts as this barrier. It's not a barrier like the sound barrier, it's more fundamental than that.

But there is a way. It turns out that Einstein developed a second theory called the General Theory of Relativity. This is actually his theory of gravity. According to Einstein, time for a clock in a gravitational field slows down. The stronger gravity is, the more time will slow down. That means that here on the surface of the earth where gravity is stronger than it is in space, a clock should actually be running slower than a clock in space.

You might ask if this has actually been shown. Once again, it's not generally well-known but it has. One of the things it turns out that this is actually part of our everyday life. I'm referring to the GPS system in your car. You know the way the GPS system works. You have a unit in your car and that unit has a clock in it and there are 24 satellites that are in geosynchronous orbits about 12,000 miles above the earth's surface. Those satellites send a signal at a certain time that reaches your unit at a certain time. We know when the signal was sent and we know when the signal was received and we also know the speed of the signal. In fact, the signal is actually traveling at the speed of light.

However, knowing time and knowing speed, you can't actually calculate distance, counter to the basic equation you learn in physics class. Here's the problem. When they were first using the system and setting it up, they found that GPS was giving the wrong distances and the wrong locations. It wasn't functioning properly. What the engineers realized once they consulted with the physicists was that they had forgotten something Einstein had said about gravity and how gravity affects time.

It turns out that the clock in your GPS unit, because it's closer to the surface of the earth, it's actually running slower than the clocks on board the satellites above the earth. So they had to use computers to calibrate the system and take into account that clocks are actually running at a faster rate on the satellites than they are here at the surface of the earth.

So we definitely know that Einstein was right, that gravity can affect time. It turns out that this effect of gravity on time can be even more dramatic, that gravity can actually be used to completely alter how times flows and it can actually cause it to twist. You can actually cause the river of time to bend and go backwards. You can twist time into a loop.

Dude. No way.

The way to think about that is that time normally for all of us moves on a straight line from the past to the present to the future. What you can show from Einstein's theory is that you can use gravity to twist time into a loop. If you twist that straight line of time into a loop, you can actually go from the past to the present to the future but you can also go from the future back into the past.

By using Einstein's General Theory of Relativity, you can create these closed loops of time and go back into the past. So the film's title connects to this idea that you can use gravity to close time in a loop which allows you to go back into the past. It's kind of interesting that the terminology in the movie referring to a future self being sent back to be killed by the past self was called "closing the loop." We haven't looped time by experiments yet, we haven't yet actually gone back into the past using Einstein's theories although there are a number of theoretical ways of doing that.

I should mention that in physics that there's a real division of labor between theoretical and experimental physics. Einstein developed the fundamental equation E = MC2 but Einstein did not build nuclear reactors or the atomic bomb. That was experimental physicists and engineers. I've been talking about theoretical work based on mathematical models and that includes my own work. I'm a theoretical physicist so I come up with basic equations that show how time loops can be created by using the gravitational effects of light. It's up to experimentalists to actually show how it works.

The other ways that one could go back in time are wormholes, another theoretical concept based on Einstein's theories, and cosmic strings, a notion developed by physicist Richard Gott at Princeton. All of these various approaches wormholes, cosmic string or using light are all anchored in Einstein's theories. We haven't developed the technology to either create wormholes. With the work that I'm doing, right now we're trying to get the funds that are necessary to show that this twisting of time can occur using lasers in a certain way.

Physics experiments are very, very expensive. Even though what they're trying to do sounds simple, it's not. For example, the large Hadron collider's whole purpose is just smashing subatomic particles together. It turns out that the machine costs close to $10 billion.

For the type of work that I'm doing, we're talking about a quarter of a million dollars just to do a feasibility study. The startup costs would run many millions more. The technology and the money are the sort of things that limit us at this present time for doing experiments that can demonstrate time travel to the past.

How feasible is it that we'll have the breakthroughs that will allow us to invent time travel in the next 30-60 years so we'll be ready when it time for us to have Loopers?

When you're talking about technological breakthroughs, the word "breakthrough" is exactly what it means. You can't predict it. There's no way of predicting when a breakthrough will happen or where it will happen. The other aspect is finance.

If you think back to the Manhattan Project, it was known from Einstein's equation that a little bit of matter would give you an enormous amount of energy. That's the basis for the atomic bomb. However, if there hadn't been the wartime need for the Manhattan Project, it's likely we still wouldn't have this weapon. What happened was multi-million dollar funding was brought to bear and some of the best scientists in the world were concentrated in this area, so this innovation was driven by necessity and a commitment of resources. Right now, we don't feel this urgency to try to develop the technology so it's hard to tell when that urgency might occur.

What would a time machine be used for? 

It could be used as an early warning device. Imagine if you had a way of sending signals back in time. That's what my work is concentrating on. Not actually sending people back in time but sending subatomic particles and information back. To me, sometimes sending information back is even more important than sending people back.Imagine if you could send information back in time and warn us of these things like Katrina and the tsunami disaster in Japan, the thousands of lives we could save by doing that. As an early warning system, a time machine would be invaluable.

Part of technological development is driven by necessity and funding. In the movie, one would have to posit that there had been some accidental breakthrough that someone found that could simplify the process. That's very possible.

Messes from the future get disposed of in the past.

In other words, right now it appears as though it would require an enormous amount of energy in order to go back in time. Going back in time is much more complicated and much more sophisticated than going into the future. It could happen that technological developments could occur that we didn't even think about that could do this. In fact, for me, that's one of the reasons why for the work that I'm doing that I'd really like to have more funding because when you're studying these things sometimes you stumble on a technological approach that allows you to take a leap forward from where you were originally and that's not something you can predict.  In the movie, one could simply have supposed that, in the meantime, some sort of major technological breakthrough had happened that had allowed the process to occur.

What about the classic objection to scifi stories: if time travel is going to be invented in the future, wouldn't we know about it already since we should have already met people who traveled from the future?

No. That's a misleading idea. In the movie, time travel to the past is outlawed because of the potential paradoxes that could arise. That is actually understandable. We really don't know what is going to happen when we're able to time travel into the past because there are two very different alternatives to what can happen.

Take the famous grandfather paradox, which I like to think of in a milder form in that you go back in the past and prevent your grandparents from meeting each other rather than go back in the past and kill your grandfather. Let's say you go back in the past and prevent your grandparents from meeting each other. They don't have your parents and then your parents don't have you. If they don't have you, how could you go back? That's the classic grandfather paradox.

There is a way out of that paradox that's actually in physics itself. What we've been talking about so far is Einstein's relativity theory. The other basic pillar of modern physics is quantum theory. It turns out that quantum mechanics does allow for an alternative possibility that's based on the concept of parallel universes.

This notion of parallel universes sounds weird but it's solidly based in quantum physics. It's based on the idea that if you apply quantum mechanics to the universe as a whole, it leads to the concept of parallel universes, which was developed way back in 1957 by a man named Hugh Everett III at Princeton. It's also called "many worlds."

You're going to regret that cheeseburger.

It allows for all different alternatives to occur but in different universes. To give you a simple example, let's suppose that today you were trying to decide whether to have a tuna sandwich or cheeseburger. At the very moment when you choose the cheeseburger, there is a you in another universe that has chosen the tuna sandwich. At the moment you make the decision, there is a split of the universe and now there are two separate universes: there's the you that has the cheeseburger in one universe and the you that has the tuna sandwich in the other universe. They don't know about each other.

This happens for every decision you make. It's mind-boggling and it doesn't have to do with just human decision-making. If you're talking about an electron, for example, an electron has two different paths it could take. It takes both paths but in two separate universes. This concept of parallel universes has actually been applied to time travel.

The man who first championed this idea was David Deutsch, a professor of physics at Oxford. When you go back into the past, at the moment you arrive in the past, there's a split of the universe: you arrive at a parallel universe and, in that parallel universe, you can do something like prevent your grandparents from meeting each other. You would just simply find yourself in a weird universe in which you wouldn't be born but yet you're there. When you arrive in that universe, the original universe you came from is unaffected. It's a separate universe and it goes on and gives rise to you in the way things normally would.

What this means is that you can travel back to the past, but the past you arrive in is not the past that you came from and that's the parallel universe interpretation of how time travel might happen. That way there's no paradox because you don't affect the universe that you came from.

Since you made it this far, enjoy this photo of Emily Blunt looking hot with a shotgun.

The movie doesn't deal with that particular resolution. One of the things that we really don't know is that we really won't know which of these alternatives happen. We really could have a situation in which reality could be so weird that the reality we think we're experiencing right now is a reality that has been changed by a time traveler and we wouldn't really know that because we would have assumed that everything that has been happening up to this particular point has been the way that it always has been.

We have those two different possibilities. We have a possibility of paradoxes or a possibility of going into a parallel universe. Both of these results are a part of physics and we really don't know what's going to occur until we actually do the experiment.


Some other physicists talk about time travel in Looper.

Thanks to Dr. Mallett for the science lesson. Let us know if you learned anything or if Looper made sense to you once you've had a chance to check it out.

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