It was the London Millennium Bridge. Here is a video of the effect in action: https://www.youtube.com/watch?v=gQK21572oSU https://www.youtube.com/watch?v=gQK215

It was the London Millennium Bridge. Here is a video of the effect in action: https://www.youtube.com/watch?v=gQK21572oSU https://www.youtube.com/watch?v=gQK21572oSU Here the problem is attributed to the peoples reaction. The evidence from the metronomes might suggest that it has nothing to do with people. The fix involves changing the natural frequency of the bridge.