Image created by Janka, 6/23/2012

Why A Working Time Travel Machine Implies That There’s No Such Thing As Free Will

Part 1: Waves and Superposition
Part 2: Basic Quantum Mechanics: Young’s Double Slit Experiment
Part 3: Basic Quantum Mechanics: The Structure of Hydrogen
Part 4: Spacetime and Wormholes
Part 5: The Death of Free Will

We’re finally at the point of talking about free will! Before I begin, I’d like to say “thank you” for sticking through this! We’ve had to go over quite a bit of physics, but it’s all been in preparation for this final post.

Temporal Loops, and the Death of Free Will

So, I noted in my last post that our time machine, by virtue of its ability to transfer physical items, must connect the physical space of the present to the physical space of the past; I also noted that this creates the potential for an object to travel along a looped path through the wormhole/time machine. However, if the object is an electron or another subatomic particle, then we’ve seen this situation before — in the hydrogen atom! The electron should act like a wave as it circles through the time machine — just as it did in the hydrogen atom; in the same way, it can and will interfere with itself. However, we haven’t introduced any new physics here, which means that the same rules that limited the electron in the hydrogen atom should also apply to the electron moving through the time machine — destructive interference is not allowed. The electron will naturally fall into stationary states — except these states extend over both space and time. “Past” and “future” cease to have meaning for that electron; the electron was, is, and will be in a fixed state that extends over the entirety of the temporal loop. More importantly, because this fixed state encompasses the entirety of the electron’s existence, it does not and can not change.

Now, so far we’ve limited ourselves to a single object (a subatomic particle, more specifically) that has actually traveled through the wormhole. It certainly has no choices due to this trip. However, it may not be clear why this would limit the free will of everything else — such as an object that does not travel through the wormhole, or even one that is completely unaware of the time machine’s existence. There are two parallel arguments that address this point. First, most physicists accept a very basic assumption about physics — that the laws of physics that exist here actually exist everywhere. In other words, there’s nothing particularly special about how nature works here as opposed to anywhere else; the same laws govern the behavior of space, time, and matter regardless of where you are in the universe. If that’s true, then the temporal stationary states that we should observe due to the wormhole can’t be simply a peculiarity of the physics around the wormhole; they must be part and parcel of how the universe works. That is, if the wormhole exists, then all particles can interfere with themselves in time, and thus inhabit temporal stationary states. In other words, the fundamental physics that applies to the particle going through the time machine effective applies to every particle in the universe.

However, we don’t have to rely upon this assumption. In our discussion of the delayed choice quantum eraser, I pointed out that quantum mechanical entanglement seems to act instantaneously over vast, perhaps infinite, distances. If that’s true, then every particle that exhibits wave-like behavior (which is all of them) has the potential to interact with the time machine; that potential for interaction will act just like peeking did for the double-slit experiment, and again force the particles into a given state. (This property is also why it does not matter how far apart — in time or space — the ends of the wormhole are. Quantum mechanical effects ignore that distance.) In either case, the existence of the time machine effectively nails time down; all particles are forced into stationary (non-changing) states with respect to time.

So, if time machines can’t exist, then free will is safe?

Well… not exactly. Strictly speaking, the existence of the time machine doesn’t eliminate free will; instead, it serves as a method for measuring the possibility for time-spanning self-interference effects. It’s the possibility of such effects that kills free will. It may very well be that these effects are possible in our Universe, even though time travel is not. In this case, we also do not possess free will — we are simply acting out the script of a play that exists, has always existed, and will always exist. We just don’t have access to enough evidence to convincingly make the argument.

One last point, for those of you who have been paying attention: an electron in the hydrogen atom has a choice of a series of possible stationary states that it can occupy; transitions between these states lead to the color spectra that Neils Bohr was trying to explain with his planetary orbit model. It’s quite possible that even in the case of the time machine there are a series of temporal stationary states that the universe could inhabit, each of which would be perfectly self-consistent. Unfortunately, it’s unlikely that the universe would ever switch from one such state to another; the hydrogen atom can only do it by interacting with an external entity — the electromagnetic field. For our universe to transition between states, it would also have to interact with an external entity.

Any hypothetical analysis I could make about such an entity will have to wait for another blog series.