This is Part 1 in a series on the physics of free will.

Check this out. There are some experiments that just make you…stop. That make you reconsider everything you’ve ever known. The kind of experiment where you just need to step outside into the cold air with your favorite beer or kind of cheese or perhaps both and just state at nothing for a while.

And for me, one of those experiments was conducted by Benjamin Libet in the 1980’s. He wired people up and asked them to just randomly flick their wrist whenever they felt like it. Totally random, totally their choice. He was measuring something called the “readiness potential,” which is a buildup of electrical signals in the brain just before you start moving. It’s like the brain gearing up for action before it sends the signal down the nerves to make the movement happen.

This was all well known for a couple decades and all fine and a bit boring, but Libet added a twist. He had his subjects watch a clock, and to note the time on the clock when they first felt the conscious sensation to move. In other words, he asked them to keep track of WHEN they decided to flick their wrists. Then he compared that to when the buildup of the readiness potential happened…and it was later.

I’m not kidding. According to all these measurements, the participants decided to flick their wrist (in the sense that they were consciously aware of their random choice) 1/5th of a second AFTER the brain had already begun the process of flicking the wrist.

Go step outside if you need to. I’ll be right here when you get back.

There is no settled answer to this experiment. It could be that free will is an illusion, and we just THINK we’re making choices when really our brains are following a pre-programmed script set down by the laws of physics. Or maybe the readiness potential is just that – a READINESS that preps the brain to activate in the potential for movement, but doesn’t necessarily always lead to movement. Or…or maybe it’s something more complex.

There’s no settled answer to the entire question of free will. We’ve kind of been debating it for…let me see here…yup, pretty much all of history. And probably longer.

Now, I’m a lot of things. Cosmologist. Science communicator. Devoted husband and parent. Amateur cheese enthusiast. But I’m also not a lot of things. I’m not a neurologist. I’m not a psychologist. I’m not a philosopher (although side nitpick, PhD literally stands for philosophy doctor, all scientists are automatically philosophers, just a specialized BRANCH of philosophy, so to clarify I’m a specialist WITHIN that branch, and not an expert at other branches). What this means is that unlike, I don’t know, supernova explosions or neutrino mass, I can’t give you an answer to this question. And I suspect that I, as a physicist, can’t EVER give you an answer to this question. And you should be really, really cautious when anybody says that they DO have an answer, especially if they start their answer with “I’m a physicist.”

But what we CAN do is explore what physics has to say about the subject. Which, while not arriving at a full answer, is still a LOT.

And the FIRST thing that physics says is that the universe is – ahem – causally deterministic, which is way stricter than casually deterministic. Causal determinism is a mouthful, but what it means is that physics works. Every effect has a cause. A leads to B leads to C leads to a star blowing up or some molecules folding into a protein. And we have laws of physics to guide us. Ever since Galileo started the program of applying mathematics to physics (and yes, I really need to do a Galileo episode, and I think I’ve been saying that for a couple years now), we’ve become ever more sophisticated in our ability to a) describe natural processes with clever theories, and b) use those clever theories to predict what the future will hold.

The greatest articulation of this concept comes to us from Pierre-Simon Laplace, the “newton of France” who was smart enough to survive both the French revolution and the rise AND fall of Napoleon, and in the meantime contribute to almost every single area of science because that’s just what Laplace does.

Laplace asked us to imagine a super-intelligent being, which today we call Laplace’s Demon because that sounds sick as hell, that could take a snapshot of the position and momentum of every single particle in the universe. And from there, the Demon could apply Newton’s laws of motion to predict every single act that would ever occur in the future. Here’s a bit translated from his 1815 “Philosophical Essay on Probabilities”:

We may regard the present state of the universe as the effect of its past and the cause of its future. An intellect which at a certain moment would know all forces that set nature in motion, and all positions of all items of which nature is composed, if this intellect were also vast enough to submit these data to analysis, it would embrace in a single formula the movements of the greatest bodies of the universe and those of the tiniest atom; for such an intellect nothing would be uncertain and the future just like the past could be present before its eyes.

So yeah, where’s the free will? There ain’t none. Or even room for the divine. When Laplace once presented his work, Mecanique Celeste, to Napoleon, the emperor asked him why “he never even mentioned its Creator” (that is, God). Laplace’s response: “I had no need of that hypothesis.”

Dang dude, tell us how you really feel.