> Order from chaos! And without any external source of energy.
It's important to understand that a physical system will seek its lowest energy level, and in this experiment, all pendulums synchronized is a lower kinetic energy level than unsynchronized.
> I wonder what other physical phenomena emerge this way.
There are many. A classic example is a phase-locked loop, in which a local oscillator will fall naturally into synchronization with a remote signal source. Again, the synchronized energy level is lower than unsynchronized.
It's important to say that, if it went the other way, if unsynchronized represented a lower energy level, getting synchronization would be very difficult.
Feynman started by investigating the wobbles of a spinning plate, and ended up with Quantum Electrodynamics. Looking at the metronome video, I found myself thinking, "There's got to be something deep there".
It'd be really cool if the metronomes turned out to be a model of the quantum vacuum, and the patterns running though the array of oscillators turned out to be virtual particles winking into and out of existence. (Hey, I can dream, can't I?)
I think you're right about the magnetic fields. I'm pretty sure the interactions between the metronomes in the video can be modelled as message passing between nodes in a square lattice of variables, with stronger association potentials in the direction of the swing than in the direction perpendicular to it.
As far as I understand it, this is similar to the Ising model of ferro-magnetism [1], where magnetism arises from the interactions of neighbouring atoms.
For more on this kind of stuff, look into graphical models. Coursera has a Stanford course with Daphne Koller on it.
Uh, no. The article points out the metronomes are on a suspended table. Each metronome adds energy to the table in phase with its cycle, as more metronomes get into phase, their summed energy edition begins to push back on other metronomes bringing them all into alignment. By the end of the video you can see the table is oscillating exactly out of phase with the metronomes as expected by that point.
What difference does that make? The metronomes and table are a closed system, so the fact that energy is transferred between them is moot.
I think lutusp's explanation makes a lot more sense: that when the metronomes sync up, they're at a lower energy level. They spend energy to decrease entropy.
I wonder what other physical phenomena emerge this way. Magnetic fields, I bet.