In theatres September 28th, 2012 is a film that moves forward only to fall back in time with Bruce Willis and Joseph-Gordon Levitt in LOOPER. The year is 2072 and the mob had control in an unusual way. To make someone disappear, they are kidnapped and sent back in time where a hit man waits. Now, someone wants to ‘close the loop’ and a man must come face to face with himself to change everything.

Time travel is the subject of so many books, articles, study and film. There is only one way to find out the truth about time travel! Dr. Edward Farhi is a physicist at MIT who knows a thing or two about theoretical particle physics, astrophysics, general relativity and quantum mechanics and even spent time at CERN. Now, as scary as all that sounds what I found is that Dr. Farhi has a great sense of humor and a way of explaining the answer to the question we all want to know – is time travel possible?

Thanks for taking the time to talk with me today.


So lets talk about time travel. I’ve read your research interests and I enjoyed reading it. You worked at CERN?

Yes, that was exciting and I was there for two years.

That’s impressive! So you are the man to ask, what is your theory about time travel? Is it or is it not possible?

Lets chat about that. In 1905 Einstein proposed the special theory of relativity and he said that the rate at which clocks run can depend on the speed of the observer or the speed of the system. When he was talking about the rate at which clocks run, he was actually talking about the actual flow of time. Not just how it feels but the actual flow of time. The affect that is most dramatic is when you move close to the speed of light. The speed of light is moving 186,000 miles a second so it’s very, very fast. If you send a light beam to the moon in a second and a half because obviously light travels much faster than rockets. Astronauts aren’t going the speed of light. There is a tiny effect if you go much less than the speed of light but it gets dramatic if you go closer to the speed of light and it’s dramatic enough that if I put you on a rocket and send you closer to the speed of light – you would come back to earth and you might say three months have passed but we on earth would say 100 years have passed.

What? Whoa!

That would mean that you skipped into the future and if you have kids they would be gone and their children would be gone and maybe you’d meet your great-grandchildren who would be around. That would be okay by the law of physics skipping into the future. So, for example at CERN, where particles are brought close to the speed of light, they take into account the fact that the clocks carried by those little particles are running at a different rate or CERN wouldn’t work. You know what GPS satellites are?

Yes, I can’t get across town without it now.

When you are in your car and want to locate or get your bearings you triangulate with a satellite. It finds your position but in order to do that it’s very important that when the signal goes to the satellite, it has a clock on it that marks the signal and it’s important that the clocks on the satellite match the ones on earth. If they didn’t take into account the fact that the clock is moving because it’s in orbit, then the GPS system wouldn’t work properly – you’d be driving off the road.

This is something extremely good to know!

Absolutely, these effects are real. They affect your whole life and you don’t even know it. It allows you to skip into the future. There is another way you can skip into the future and that’s by going into a strong gravitational field. In 1917 Einstein proposed a general theory of relativity and it says that objects that are put into strong gravitational fields can run at different rates. So another way I can project you into the future is by lowering you into a strong gravitational field. If I did that your biological clocks would start to run slower and you’d age less than people on earth. If you came back to earth 1,000 years might have passed depending on how we set it up so you’d be returning from the future. That’s very much allowed by the laws of physics.

And going back?

That’s where it gets a little complicated going back in time. Even though I can let you skip forward, if you wanted to return that’s much more problematic. The reason for that is if you go backward in time from the future back to now, you could go from now back into the past. If I’m allowing to backward time travel why shouldn’t I let you do it now? If you could go back now you might kill your grandparents before they made your mother and it would be very hard to understand how you could exist. Backward time travel is much more difficult. Just because it’s paradoxical or weird doesn’t mean we shouldn’t believe it isn’t possible.

Can you expand on that?

Let me tell you an experience with this; once I was looking at a paper on how a guy had constructed mathematically a system on paper and he could show that this system warped space and time around it enough that it would be possible to encircle the object and return back before you left. That’s backward time travel. I was very turned on by this because it looked right so I talked to my colleague Alan Booth and another colleague Sean Carol and we looked at it very carefully. We didn’t ask if it was about solution but we asked a different question – can you build it? Assuming unlimited technological ability but always obeying the laws of physics, never violating anything that we talk as the principle of physics, could you still build the object? We discovered that in order to build the object you needed to assemble half the mass of the universe.

Half the mass of the universe?

Yes! That seemed daunting so we wrote a paper called “The Obstacles to Building a Time Machine in the Laboratory”. Nonetheless we were entertaining it and while we were doing that another guy came along and looked at it very carefully and said, “if you guys built this thing and you attempt to encircle it, before you return to your starting point before you left, the whole universe that this thing is in will collapse and crunch”. The crunch is the opposite of the big bang. That really seemed like the laws of physics were conspiring to prevent the backward in time travel instead of allowing it decided to think ‘lets just terminate the universe’.

Well played!

In that case we convinced ourselves that backward time travel wasn’t going to happen.

So you see it as the universe protecting itself?

I think that’s right; the universe protected itself from what we would call causality violation.

Knowing what you know about all this, when you watch films with time travel, does it intrigue you or amuse you?

I recently saw BILL & TED’S EXCELLENT ADVENTURE and I liked it. I was taken in by it and was charming. It wasn’t mean spirited so it was a nice movie. I find the fact that it probably wasn’t okay with the laws of physics to go back and bring Napoleon forward, that didn’t really bother me. I overlooked it and shoved my scientific skepticism aside. I’ve seen CONTACT with Jodie Foster.

Do you find yourself picking time travel movies apart a little?

A little bit but I can do that pretty fast in my head and then try to ignore it.

So with BACK TO THE FUTURE, do you see anything in there that amuses you or peaks your interest?

The DeLorean does. We here at MIT decided to try to see if time travel was possible so one way to test that was to see if you could tempt a time traveler to your current location. It would be nice to meet a time traveler from the future and it would give evidence that time travel was possible. So we had a time traveler convention and we put out milk and cookies and another thing future time travelers would want and we had a DeLorean and we waited. I hate to say this but a time traveler from the future did not show! So that proves time travel is impossible.

“Milk and Cookies Proves Time Travel is Impossible” is a good title for a paper on time travel.


I have a question, or a thought actually, if you were to go into the future and kill your older self – theoretically doesn’t that cancel you out?

Yes, I’m going to agree with you.

I’ve seen time travel movies that say you can’t meet your future self or past self?

That would be a way out of it. If you could backward time travel and kill family members but that would cancel yourself. So some people have speculated that if you go back in time you can only do things that would not affect the future. I don’t know how you could legislate that.

Human nature would say I want to see me? If you see yourself do you go in such a state of shock that you burst into flames?

That would be good, that would take care of it.

And that takes care of this conversation on time travel and I’m completely up to date and stress free about time travel. Although most of us have, at one time or another, thought about it, it doesn’t seem the universe is going to allow it. We are always told to look forward and not back so the universe has seen to it that we follow the rules.

But that doesn’t stop us all from enjoying a film about it, especially when Bruce Willis and Joseph Gordon-Levitt meet face-to-face. Added to the cast are Emily Blunt, Jeff Daniels, Paul Dano and Piper Perabo. Opening in theatres September 29, 2012 is LOOPER.

In the end – face your past and fight your future!



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