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This is a normal post Excellent
This is science in action, so how does it work then?
 (I helped save b3ta! Brandy_Bumwinkle, Fri 2 May 2008, 12:30, , Reply)
This is a normal post I'd expect
that the inertia of the swing arm movements is causing the plinth to roll slightly so that when they get to the end of their swing it gives them an extra split second of balance (like the zenith of an object that's been thrown in the air). The other arms (in the middle of their swing) then have time to catch up. As more of them sync up, the plinth moves more, as in a feedback system.

Or not.

But it's feckin' cool, and I'll bet I've got enough swing arm metronomes lying around at home. I'm trying this one out :)
 (I helped save b3ta! masakatsu best of all the burger meats, Fri 2 May 2008, 12:36, , Reply)
This is a normal post Yes, I was thinking 'roughly' the same thing :)
I only have one metronome but this makes me want more, more! Any suggestions on a variation using normal household crap laying around?
 (I helped save b3ta! Brandy_Bumwinkle, Fri 2 May 2008, 12:38, , Reply)
This is a normal post Probably
any pendulum (newtons cradles etc) would most likely have the same effect. If you make a few equal length pendulums using string and something for weights, it should work.
 (I helped save b3ta! masakatsu best of all the burger meats, Fri 2 May 2008, 12:42, , Reply)
This is a normal post ^ What he said

(I helped save b3ta! redazril I LIKE DRUGS!, Fri 2 May 2008, 12:53, , Reply)
This is a normal post A techie explanation...
In a system of linear oscillators like this one, the motion can be described by the sum of a set of "modes", each of which oscillates at a single frequency. At the beginning, the oscillators are effectively uncoupled (they'll be weakly coupled through the table, but this is too heavy to really make a difference). There are therefore 5 modes, each describing a single metronome oscillating at its own frequency. When the metronomes are put on a common board, which is capable of moving from side to side, the modes will become coupled and will describe the motion of all the metronomes in some way. Key is that the different modes lose energy at different rates due to non-linear effects (damping). The motion that you see at the end, with all the metronomes in sych is a single mode and it happens to be the one that loses energy the slowest. All the other modes therefore die away leaving only that motion being observed.
 (Mr T, Wed 7 May 2008, 16:54, , Reply)