How Can Action Be Understood in Human Terms?

[Upisoft]

But, to give an example, out of my free will, I am choosing "otherwise" - that is not to continue my participation in this particular thread, even if I have started it.

Your example failed.

 

[arkajad]

Your example failed.

Of course. Did you expect otherwise? After all I am a human being not some perfect machine.

 

[ConradDJ]

Well, each particle is just looking at the local geometry (gauge fields, gravitational fields), checks its position and speed, and calculates the next step. Runge-Kutta of some order works well for a small number of particles and not too long times.

That's the whole point: in classical physics least action is equivalent to second-order differential equations.

In quantum theory the computation is enormously more complicated. That is why people have hope in quantum computers since Nature does it seemingly effortlessly.

The calculation is more complicated for us, when we try to compute probabilities in quantum physics. But I doubt that Nature is doing any numerical computations -- it certainly doesn't appear to be set up to do that.

Quantum "computation" seems to work in a different way. When two particles interact, everything that could possibly happen happens, but nearly all the possibilities get "taken out" in some sense by other possibilities with opposite phase. Of the remaining possibilities for interaction where the phases reinforce, the two particles randomly agree on one, as what "really happens" between them.

Actually the superposition of possibilities never gets "reduced" to a single, classically well-defined reality. In QM there is definite information only to the extent it's "relevant" -- i.e makes a measurable difference.

But without getting into the whole question of measurement -- my point is that this quantum set-up can maybe determine the dynamics of very complex systems "by feel", so to speak -- through a combination of phase-cancellation and random selection. No numerical calculation required.

A fanciful thought, but easier for me to imagine than your particle doing the equations "in its head."

 

[Upisoft]

Of course. Did you expect otherwise? After all I am a human being not some perfect machine.

I did not expect otherwise. You thought you can choose otherwise, but you couldn't. You were controlled by your imperfectness.

 

[arkajad]

Perfect things are essentially dead or dying - so they are not that perfect after all. The universe is alive because the perfect symmetry is broken. And that is why it is interesting rather than dull.