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Posted by: Phil66 Sep 30 2015, 09:49 PM

All set to the same rhythm but started at different times and ending up synchronised all on their own. This was first discovered in 1670 by pendulum clock inventor Christiaan Huygens.
Before Huygens closed up shop for a long weekend, he wound up all the pendulum clocks hanging on his wall, and set them to tick-tocking back and forth, none of the pendulums swinging together. When he returned, Huygens was astonished to discover that all of the pendulums were perfectly synchronized, swinging together tight as Duke Ellington’s rhythm section . Huygens had discovered what we now call entrainment, the tendency of things to vibrate at the same frequency.
Watch entrainment happen before your very eyes

Posted by: Mertay Sep 30 2015, 11:28 PM

Video link didn't work for me but I heard it before. 2-3 weeks ago in a documentary I watched it mentioned they're getting close to the math as to explaining this but basically its the wall or floor that transmits vibration and enables them to sync.

Posted by: Phil66 Oct 1 2015, 08:13 AM

Thanks Mertay,
I've embedded a YT now.
I can kind of understand how it happens but I'd like to see what happens if exactly half of the metronomes were started one way and the other half the other way at the same time. I bet they would stay as they are because of equal and opposite forces.

Posted by: jstcrsn Oct 1 2015, 12:13 PM

QUOTE (Mertay @ Sep 30 2015, 11:28 PM)

Posted by: Phil66 Oct 1 2015, 12:48 PM

Yes I noticed that. I think it would still happen on a solid table because vibration is hard to eliminate. Huygens discovered it after leaving pendulum clocks for a long weekend. Maybe on an ultra solid table it would take weeks. It is definitely a proven scientific phenomenon though. Maybe the not so solid table was to speed up the demo?

Posted by: Gabriel Leopardi Oct 2 2015, 02:46 PM

Awesome! I've never heard about this. It's not exactly on topic but this thread made me remember this movie:

Posted by: Sensible Jones Oct 2 2015, 03:32 PM

What a great demonstration!!
It's a similar concept to what happened with the Millenium Bridge in London. They couldn't understand why it inherited a terrible wobbling effect when in use. They then discovered that it was caused because all the people crossing it tended to fall into step with each other thus causing a regular vibration all along the Bridge which the caused the wobble!

Posted by: klasaine Oct 2 2015, 03:48 PM

When an army crosses a bridge they fall 'out' of step for that very reason.

*Great book ... https://books.google.com/books?id=Bwd-MHINMGsC