Concerning Time Travel

After watching the trailer for Looper, the upcoming film in which a young man (Joseph Gordon-Levitt) is tasked with assassinating the older version of himself (Bruce Willis) who travels back in time, I started thinking quite a lot about the concepts of time travel. This led me to two major thoughts.

First, I really am a nerd for spending so much time pondering the practicalities of time travel.

Second, I am convinced that time travel will never become a reality, at least not as it’s depicted in the movies.

The first major problem involves the challenges of moving mass across time and space.

In the trailer for Looper, we see JGL standing in a field smoking a cigarette. In an instant, Bruce Willis, the older version of himself from the future, appears before him. Poof! There he sits. Not only is he there, but he has the wherewithal to instantly recognize the danger he is in and react quickly enough to save himself from being shot. He is seemingly unfazed by the ordeal of traveling back in time 30 years. The question arises: how did he get there?

One way is to fire him into a wormhole. We’ve seen this in several movies such as Timecop, Terminator, Back to the Future, and even Contact, which was based on real-life physicists Carl Sagan’s novel. In each of these films there is some way to connect the endpoints of the wormhole and some device that actually transports the person through it. It’s a cart in Timecop, an energy field in Terminator, an alien construct in Contact and the DeLorean in Back to the Future.

Your ride awaits!

On paper, creating a wormhole is a reasonably sound concept. The Einstein-Rosen Bridge seen in Thor is a real concept of physics, and it is theoretically possible to connect multiple points in space and time. You can’t just send a man or demi-god hurtling through an Einstein-Rosen Bridge with nothing but the clothes on his back as Thor did, unless you want to vaporize him with intense energy bursts and pressure, but you can at least theoretically build the bridge. Work with particle accelerators like CERN’s Large Hadron Collider is solidifying many small-scale concepts of particle physics. The physics community is developing a rich understanding of both the large-scale theory and small-scale properties that could result in the formation of artificial wormholes. We know that small wormholes do exist for brief time periods, and it is possible that devices that create wormholes could be developed in the near future. Issues of stability, size, and duration would need to be addressed, but as science progresses, these are the types of things that usually sort themselves out. Once you find a way to create the wormholes, the rest are just details.

An Einstein-Rosen Bridge

One of the major details then becomes how to position the wormhole. In Looper and Terminator, the person or robot (excuse me - cybernetic organism) being moved through the wormhole is placed precisely in no less than four dimensions. And, who can say how many dimensions were actually navigated by the wormhole since one of the common theories of physics is that there are a number of ‘hidden’ dimensions that we simply don’t notice. It would require very precise information to hit a specific mark on the planet at a specific point in time. Such highly refined data doesn’t exist.

We’re not talking about punching in a set of latitude and longitude coordinates and a date. It’s vastly more complicated than that. Remember, our planet is rotating on a tilted axis, which is moving in an elliptical orbit around Sol, which is in turn moving around the Milky Way, which is in turn expanding across the cosmos. How hard will it be to precisely place your wormhole with all of that motion? There probably isn’t a system available to match up all that movement in both time and space to just drop somebody down where you want them. Simply punching in a lat and long in the year 1861 would very likely drop your Terminator or DeLorean into deep space, because the Earth wasn’t anywhere near its present location in space 150 years ago.

The good news is that, if you were to somehow find a way to position it, there is a class of wormholes that are traversable. The earliest theorized were not. Early theories recognized that black holes could connect multiple points in time and space. Of course, you can’t travel through a black hole. Once you cross the event horizon, you are pulled, stretched like taffy, by an immense gravitational field that ends in a singularity at the bottom of the hole. You can enter a black hole, but you can’t come out the other side.

A paper in the American Journal of Physics by Morris and Thorne in 1988 described traversable wormholes. The central challenge of traversing their theorized wormholes lies at the center of the wormhole. At this point, the pressure is immense and there is a huge energy cost on material passing through it. However, they postulated that there could be some heretofore-undiscovered material that could withstand the challenge. Essentially, you could shield your passenger with this exotic material and send them on through. Their class of wormholes avoided the many pitfalls of black holes, such as eliminating the event horizon and offering stability, small tidal gravitational forces, and short time of transit. Also, they don’t end in singularities and allow material to emerge unscathed on the other side.

To summarize, to pass through a wormhole, you need to create one very precisely in time and space and shield your passenger with material that is not known to exist so that he isn’t obliterated in transit.

That’s not to say that tranport through wormholes can’t happen, but it doesn’t seem very likely that all of these elements come into place any time soon. There is still a lot of physics ground to cover between now and then. However, it is impossible to reject the possibility of time travel through wormholes. Maybe physicists will get there one day.

Steven Hawking, a much smarter man than me, and someone who knows a thing or two about physics, believes time travel is possible, but only in one direction. Time travel into the past cannot happen; we can only go into the future. As we know, gravity has the ability to slow time. The Theory of Relativity predicts this. If you orbit a black hole just outside the event horizon, the time experienced by those in orbit is less than that experienced by outsiders. So, if you spend five years orbiting a black hole, the rest of the universe will have experienced ten years of time. Upon leaving the vicinity of the black hole, our orbiters would enter a universe that is five years into the future. Unfortunately, there is no theoretical way to make this work in the opposite direction and go backward in time.

Steven Hawking, a guy who actually knows what he's talking about. 

You can also achieve the same effect by traveling at or near the speed of light. If you traveled at such high speeds, you would experience only a brief amount of time while others in the universe would experience a much longer amount of time. Again, this lets you travel into the future, not the past.

Click here to read what Hawking thinks about time travel.

However, the Morris and Thorne (1988) theories on wormholes do postulate two-way travel. So, maybe there is a way to go forwards and backwards in time.

It seems the most likely method for time travel would be to develop ‘portals’, centers that provide an anchor point for your wormholes. Think Stargate. These gateways would provide stable, known points in the universe where wormholes could be opened, material could pass through, and then the wormhole closed in a controlled environment. Actually, that sounds exactly like Stargate. Such areas would be developed in the future and would only allow time travel from the time of their completion on.

Step into the wormhole.

Let’s imagine that scenario.

You are a high-level physicist working at an ultra-top-secret military installation (because who else will pull this off but the military, and you know they’re going to keep it secret from everyone for as long as they can). In the bottom of a bunker deep underground, you build some crazy contraption that is designed to open a wormhole with itself in the future. All the diagnostics and simulations have passed their tests, and you’re convinced that your technology will work. You flip the switch to turn it on and a wormhole opens, a high-energy time-tunnel that connects the device with that very room one week further in time. You send a message through to yourself saying that all systems are go. A few minutes later and the system fires up again. This time it receives a message. One sent by you from the future saying, essentially, “Hell yes it works!”.

How awesome would that experience be?! You would know instantly if it worked because you would be able to tell yourself all about it from the future. Sweet!

I imagine that this point, when we render time itself obsolete, that we will declare a new era of civilization. Events will be recorded in terms of “before time travel” (our current era) and “after time travel”.  It may sound grandiose, but let’s face it, the ability to bounce back and forth in time is a major deal. The ramifications of time travel are immense (and beyond the scope of my current ramblings).

Ultimately, it seems like the only way that time travel happens is if we send stuff into the future or build wormhole machines at some later date.

I do not believe that we can send things back to the past without first inventing the correct portals.

Which leads me to my second point about time travel.

If time travel allowed us to jump backwards as is seen in Looper or Back to the Future, then we would already know that time travel was possible. If people had traveled back in time to our past, then there would be signs of their visits. Weird, unexplained technology would litter the landscape. Haven’t you seen Terminator 2?

Did you leave something behind, Arnold?

In that film, remnants of Schwarzenegger’s first visit as a Cyberdyne Systems Model 101 are recovered by the Cyberdyne Company and used to make the very technological breakthroughs that would lead to the development of the Model 101. Paradox alert! In fact, there would currently be lots of these paradoxical quandaries if time travel existed. Even if time travelers took great care to leave nothing behind, nobody is perfect. Artifacts of all sorts would be lying about causing us to puzzle over their origins. We may at first think the technology as alien, but as soon as we find a scrap of paper written in a language we understand, we would catch on. Then all future technological research would be geared with time travel in mind. What would happen if someone forgot their iPhone in the 1750s? Ben Franklin would play Angry Birds and then direct all of America's top scientists to figure out how this crazy device actually worked.

There also would be accounts of strange people with crazy tales of the future.

In 12 Monkeys, Bruce Willis (that guy must like time travel films) plays a character from the future warning of a catastrophic global disease outbreak. He comes to the past (our current day) and warns us of our impending doom. He is promptly thrown in the madhouse. Everyone thinks he is crazy. Coming back to Terminator 2, Sarah Conner warned everyone she could pin down for five minutes about the threat of global thermonuclear annihilation, but nobody would listen to the ramblings of one crazy woman. But, what if we sent back lots of people across many generations, all telling the same wild stories? We might eventually start to believe that a global catastrophe was coming. It would become part of our culture and might actually prevent disaster. The fact that there isn’t some impending doom on our minds means that we either haven’t done a good job of alerting ourselves or that nobody has actually traveled back in time to warn us.

So, the fact that we don’t know if time travel is possible means that time travel is not possible.

Ultimately, time travel may or may not be a reality. We are still too far away from the solutions to the myriad problems surrounding time travel. If it does come to pass, we won’t be going back to visit ancient Rome. We will either be going forward in time or back and forth to a point when the technology is finally available.

That’s kindof too bad. It could be a lot of fun to travel back to Greece, Egypt, feudal Japan, or Tenochtitlan when those civilizations were in their primes. Or, how sweet would it be to see New York City in the year 2100? So many possibilities for travel, yet no way to get there.

Do you think time travel could happen? How far back or forward would you go? Do you agree or disagree with my ramblings? Let me know in the comments or on Twitter!