If you listen to this show a lot, and if you haven't, it's never too late to change,

you've heard me talk about determinism.

It's this magical ability in physics to predict the future.

If you define the state, this is such a big word in physics, the state of the system, just a list of all the current properties of everything in a system.

And that's another word I use all the time in the show is system.

Like, a system is the thing you're looking at. The thing you want to understand in physics is the

system. It could be a ball on a spring. It could be a ball in a box. It could be a ball floating

around the universe. Whatever it is, it's a system and you want to understand.

And so a list of all the properties, all the positions of all the particles you're interested in,

all the forces involved, energy states, momentum, you know, electric charges, just the state.

And you can even do this in quantum mechanics, but you have to change slightly the definition of state. If you have the state and you know the laws of physics,

then you know what the states will be in the future. You can predict the future. This is

determinism. And physics is deterministic. If you know

the state and you know the laws of physics, you know what the future will be. There's no question

about it. This is all nice and neat and tidy and tied up with a neat little pretty bow. Physics is

so awesome, except when it isn't. And it isn't most of the time.

But here's the crazy part. You can have systems, you can have situations that are completely and

totally deterministic. You can know the state. You can know the laws of physics. Determinism

still rules. And yet, they are unpredictable. Determinism doesn't mean, after all, that you can predict the future.

Which seems like a paradox, right? Because that's the whole point

of determinism is to be able to predict the future. And now you're telling me that you have the

ability to predict the future and you can't. What is wrong with that? Let me give you an example.

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