Robert's Mistakes

honored scientist goes crazy, video included

Jun 13, 2013

John Horton Conway - the free will theorem

He's insightful and admits that trying to contribute substatially to another field after a successful life as an expert in one's own field is a sign for dementia. But aside from that i found this series of talks quite entertaining.

First the speaker assumes that you can create pairs of particles which are in the same state. This assumption is named TWIN.

Using three cubes he constructs a model for the Stern Gerlach quantum experiment to illustrate the puzzle of why hidden variables won't work. The task is to distribute black and white dots on the cube while respecting the SPIN rules.

If we only do say, 6 experiments on the twins, it is always possible to place those 6 black dots such that they obey the rules. But if we attempt to find a configuration which would work for all choices it turns out that it's not possible.

For mathematicians this isn't very bizarre. Think of the measurements as equations. If you have too many of them the solution space is empty. And this is what happens with our cube. Painting dots to describe all possible outcomes ahead of time cannot be done.

This is not just a mathematical trick. It is at the heart of the hidden variables puzzle. So it is nothing new either. But it is a fancy simple illustration of that fact.

After that, Conway proposes FIN to model general relativity but then simplifies that idea so there only need exist two casually separated places in spacetime where we can perform SPIN experiments on TWIN particles.

We're nearly there we just need to define clearly what free will means. Our speaker puts it like this: A free decision is one that cannot be modeled (as a function) using only the information of the past as input. That is, even if all of the past universe is the same, you could still decide otherwise.

Finally the result is this, if the choice of the experimenter is not determined by the past so isn't the state of the particle. It sort of has the same freedom as the experimenter.

This is no proof that free will exists but it shows that if our mind is free to choose then these particles shouldn't be determined either.

I really very much liked the way he argues for free will at the end. Appealing to mathematicians but, i guess, not moving physicists or philosophers an inch.

The footage was filmed at Princeton (don't know why their audience gets 6 lectures, he did it in one part on some other occasions):

You can also watch on youtube, starting here:

John H. Conway Free Will Lectures [1/6]: Free Will and Determinism in Science and Philosophy

Open ends Did you see other scientists doubting their sanity on video? Please tell me!