My Dad Explains the Science of "Source Code."

by Eric Kohn
April 4, 2011 4:12 AM
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Ever since I caught "Source Code" at an early screening last month, I haven't been able to get its time-spinning, reality-defying concepts out of my head. The movie works quite well no matter how hard of you try to understand it, but since it deals with an imaginary technology that could--if it actually existed--prevent all kinds of disasters from taking place, it's hard not to wonder what it would take to bring its underlying concept to fruition. Partly inspired by these detailed attempts to decode the movie's ending, as well as a video produced by Wired about the science behind the movie, I turned to the one person whose opinion about these things I usually trust more than any other: My dad.

A physicist who identifies himself these days as a "cyber-control scientist," my dad (whose bio you can read here) loves to dig into the feasibility of pop culture narratives. (You should've heard him dish on "Inception." He loved it.)

After the jump, the old man offers his two cents on why the science of "Source Code," sadly, comes up short. Probably.

Before seeing the movie, he watched the following video:

Knowing nothing about "Source Code" except what the video told him, here's what he wrote me:

The animation, which includes CLASSIC quantum equations like the Schroedinger equations, postulates unproved and highly controversial principles of string theory. (String theory claims that the state of the universe lives in a high dimensional space which is decomposable into many 4-dimensional space-time subspaces in which partial information of the overall state is stored.)

It is true that at the quantum level time is reversible, but this does not mean that "particles travel backwards in time." What it means is that there is a FINITE nonzero probability that any particle can be anywhere in each of the 4-dimensional space-time subspaces.

Decoherence is an important new interpretation of a quantum mechanism of DISORDER called ENTANGLEMENT, which incidentally works against the ideas of decomposition above. ENTANGLEMENT is an essential mechanism in the quantum behavior of particles.

The physical theory that would better support the ideas in the animation is the theory of quantum physics known as SUPER SELECTION. This theory explains some of the behavior of the universe by postulating a set of super selection RULES.  These rules are constraints on the dynamics of particles and their interactions. The rules introduce order (i.e., partial coherence) on the dynamic states of particles and fields (BOSONS and FERMIONS) by PREVENTING entanglement among the different space-time subspaces.

So, if a super selection rule exists that prevents entanglement between 4d space-time subspaces, and if string theory proves to be a good model of the behavior of the universe, and if this model is compatible with general relativity, the animation may be the beginning of something big! 

More later after we see the film.

So he went to see the movie with my mom. Here's a trailer:

Read the synopsis here, if you have either already seen the movie or don't mind the spoilers.

Here's what he wrote me afterward:

First of all, I enjoyed it.

I was trying to correlate the plot with the "physics." One of the huge physical errors is the violation of the second law of thermodynamics: "The internal entropy of a system" --in this case the train system-- "increases monotonically in time."

Once the first 8 minute reality happened, in the second 8 minute episode, the system should have had far more disorder (because its entropy increases monotonically over time). If the system has to be reversible, an enormous amount of ordering energy would have to be provided to revert to the initial state of the episode in a different reality. 

By the way, that video does not mention the second law of thermodynamics!

One of the glaring mistakes is that as time progresses, the universe gets more disordered. So after the first explosion, all the molecules scattered all over the place. Imagine the amount of energy that would have had to be added to the system for the second trip. And Jeffrey Wright's character doesn't even talk about the second law! Even inside the source code, the second law of thermal dynamics can't be violated. It's a fundamental principal of physics. The most order the universe ever had was when it was a single dot. After the Big Bang, from that point on, everything has been getting more disordered.

When these people died in an explosion, all their atoms--the mass--did not disappear. It just transformed into a more disordered state. It's true that time is reversible, but entropy is not. They created a disorder and they have to bring back the order in an alternative universe. I can conceive of that. But you can't violate the second law of thermodynamics.

When you blow up all these bodies on the train, you create an enormous disorder. It has to be valid in all of the realities. So the source would have to provide infinite energy to reassemble it back to the initial state.

A more realistic thing would have been "tunneling." You can tunnel from one reality to another just before the big explosion. Since the disorder has not happened yet, you can bring it back to its initial state.

Still, there are a lot of interesting ideas here. Modern physics was written with string theory, a mathematical theory that has not been proven physically. Newton's ideas were seen as alchemy before he formalized them. So maybe the idea that there are multiple realities will be proven to be valid. Reality has to be in three dimensions and time, but string theory says the universe has a much higher dimension, so it's possible that there are higher realities of the universe that you can project into other spaces.

At some point in the movie, they altered reality, and I can live with that. It's difficult to understand, even with modern physics, how that can happen. But I cannot accept the rejection of the second law of thermodynamics.

I had to explain all this to your mother, along with two other people who were at the theater and overheard us talking.

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  • Marion | September 12, 2011 4:58 AMReply

    I loved hearing your dad's perspective on this as my husband & I also loved this film but the "science" in it also sparked a furious discussion between the two of us. My observations were from a medical point of view. How could they have kept Cpt. Stevens' brain alive if his body was dead? He was not on a ventilator. The EEG leads attached to his brain could not be accessing neural activity on a dead lump of tissue....and why were they not merely accessing the last 8 minutes of Cpt. Stevens' life? (which would have been stored in his brain); how could they take one person's last 8 minutes & transfer it to another person's consciousness to access HIS last 8 minutes, without even having some of the host person's brain tissue? Presumably, if they had to have Cpt. Stevens' brain in the lab to connect his source code to that of another (also dead person), they would need the "other end" of the connection as well. They couldn't just send his consciousness out into thin air & expect it to connect with Sean Fentress every time. Why couldn't he access the last 8 minutes of any of the people who died on the train? See, even though I love the discussions on the physics of these sorts of films, I can never get past the "bad medicine", which would make everything else irrelevant anyway. Besides this, we loved the film. Hated Inception.

  • James | August 10, 2011 2:59 AMReply

    There's a short eplanation of the "biophysics". Then the inventor says source code. What is the "source code"? If the inventor says they're sending Jake to alternate realities, then why doesn't the inventor think that Jake had actually saved Christina, but in an alternate reality? If alternate reality is where Jake is sent, what importance does the host persons short term memory have? Just send Jake as himself or anyone to the A.R. and let him keep trying. Worst pseudo-science, I've ever seen.

  • JohnC | June 5, 2011 12:04 PMReply

    The film may have been fun, but the science was rubbish. It didn't fit any current theory and certainly no known science.

    I do not however agree that the second law of thermodynamics was rejected. The subject was sent (back?) to an alternative reality before the explosion. He was sent not from the point of the explosion, but from the point where he started, several horus later. Whether it was a wormhole into another parallel universe, or time travel, doesn't matter greatly.

    He had been in the program (literally) for two months, allegedly having been selected for his compatibility with the brain, ethnicity and body type of the victim. Yet the victim died only a few hours before. Even if that statement was just a tad misleading (though for what purpose?) how could this entire program be operational only a few hours only after the first explosion? And how did the facility (some people assume a company, but obviously a military facility) get all the information they had from a fireball only a few hours before? Unless they knew in advance who was on the train, and who whould die?

    Finally, doesn't the contradictory ending suggest that what is involved is a combination of time travel and mind swapping? Otherwise how can a warning be sent?

  • GRooveLlama | April 21, 2011 1:19 AMReply

    Seems almost as if the universe is nothing but a visual representation of our consciousness evolving... ever expanding as we our selves expand in equal measure.

  • DEW | April 10, 2011 1:54 AMReply

    Eric, I loved the movie and saw it after seeing a special on parallel universes and the merg of String and M-theroies being worked on now. I am by no way a scientist, but love the dabbling.

    Your fathers explaination is fantastic in many ways, but the most fantastic is that you went to him for the answers.

    Now take it to the level of the movie where the main character is being forced to save the world and the focus he has is to connect with his father to right a bad episode in their relationship. The human imagination can dream up ways to experience this through thought and scientists, physicisits and quantum theorists try to prove it. :)

    man was not supposed to fly at one time let alone go to the stars.

    you can reach back to your Dad now in the present, but what if you could not? what would you give for that one 8 min period in time to say "I love you" one more time. I know i would jump at the chance.

    finally, before the turn of the 20th centruy Scientists believed they had discoveded all they could about the universe then Physics came into play. within 20 years the atom and nuclear science were changing the way we thought about the universe. there were only 4 dimensions. Quarks and Photons did not yet exist in our understanding. Dark matter, the universe moving at an excelerated rate away from a central point etc are all being unravelled like a string. 5 string theories all existing at the same time, then M theroy what is next.

    One thing i will say is that the theory behind the movie may not meet the physics of today but may meet it tomorrow. Thanks for the article and I wish i could have been in the theater with your father. :) dew sends

  • Bryan Sanctuary | April 5, 2011 10:05 AMReply

    I enjoyed this very much. Sci-Fi might be fun, but it as your dad says, the laws of physics are often violated. I also agree with his comments about the Many Worlds interpretation of quantum mechanics. On the other hand, there are parts of physics today that accept notions like quantum weirdness or magic, that are close to Einstein's spookiness. It makes no physical sense to us (yet) how entanglement can be maintained of space-like separations. Notions that came from Bell's theorem, like non-locality and teleportation defy our understanding.

    For my part, I agree with Einstein that quantum mechanics is incomplete. In fact I found that if you allow a spin to be an anyon, then the difficulties with quantum weirdness are resolved.

  • wolf kohn | April 4, 2011 12:18 PMReply

    Adam: Try
    "Quantum Thermodynamics: Emergence of Thermodynamic Behavior Within Composite Quantum Systems"
    2nd Edition
    Jochen Gemmer, M. Michel, G. Mahler
    Springer Verlag 2008
    "Modern Quantum Mechanics"
    Revised Edition
    J. J. Sakurai
    Addison Wesley 1994

  • Adam Drew | April 4, 2011 10:23 AMReply

    Cool, thanks.

    Do you have any reading recommendations for educated non-scientists on this topic?

  • Sam "Duke" Fragoso | April 4, 2011 6:38 AMReply

    Great article Mr. Kohn

  • wolf kohn | April 4, 2011 5:52 AMReply

    Adam: Tunneling dynamics has a macroscopic effect therefore it is constrained by the second law of thermodynamics. Quantum dynamics of the particles involved in the simulation (real time over 8 min ) require that it (the simulation) reads the state of the system without DEMOLISHING it (Quantum Non Demolition measurement of the state), which would MINIMIZE the state variations from 8min simulation to the next 8min simulation. But these simulations would not be identical.

  • jen | April 4, 2011 5:33 AMReply

    wow. how did your dad like donnie darko?

  • Adam Drew | April 4, 2011 4:24 AMReply

    Wow! Now, I'm far from an expert, but I got the read that the Source Code WAS tunnelling, even if only inadvertently. Whether it was the designer's intent or not, they were running a "time travel simulation" that on fact propelled the observer into another world, identical but for his transposed consciousness. His actions, therefore, were not simulated by Source Code, but true actions in am alternate reality, which is how he is able to live on after the 8 minutes in the final"simulation".

    Would this read sidestep the 2nd Law problem?

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