I’ve been having curious thought experiments in my mind recently, so I’m committing them to paper (so to speak) here. They are related to the concept of free will, the ability for somebody to make their own choices free of external constraints. A particular thought about this I’ve been having is related to the nature of our universe and its physical systems. Does physics contradict or complicate the concept of free will?

The theory of special relativity states that the universe is made up of space-time, and that space and time are intertwined and interwoven. Observers at different locations of the universe and traveling at different speeds will be, in essence, at different points of time than each other. The faster in space you travel, the faster into time you head. It is because of this condition in relativity that, if I got into a spaceship and went out to a distant star at the speed of light, by the time I returned many, many years would have passed here on Earth. Meanwhile, I would have only aged the time I perceived in the voyage. I would have essentially flown into the future, and came back to an Earth of that future. Doing so, I would know how the future would have played out.

A major conflict arises between the idea of free will and the idea of divination, of seeing into the future. A knowledge of the future denotes that a singular set of events will happen that will lead the universe to that future. If I go into and see the future, then the past is set in stone: it must get to what I saw somehow. This indicates that the choices we make are predetermined or predestined: they must enable the future I see to happen. How much free will do I exert if I am destined to make a certain set of choices?

If I fly into space at the speed of light and come back to the future, then I am seeing history which has yet to happen. I am, in a way, seeing the future. All of my friends, everyone I ever knew, most likely everything I ever held to any importance will be long dead and gone. And yet, I will still be young, having aged much slower and at a different perception of time. Which reality is ‘correct’, then? The one where much time has passed while I was gone on my flight, or the one of me sitting on my ship? If they are both one reality, then that means that the future will be open to me to perceive, and thus set in stone.

Traveling beyond the speed of light is a physical impossibility, but getting very near to it, and being influenced by the time-bending effects of special relativity, is within the realm of physical capability. Therefore, this is not just some sort of hypothetical thought experiment. It has real implications. Time is not universal and therefore the past, present, and future is not set. If this is the case, then perhaps free will does not actually exist. If we cannot make our own decisions and have them be completely ours to make, without external causalities or constraints influencing us, then perhaps our will isn’t so free after all.