Researchers found that pedestrian bridges don’t become more unstable as more people walk over them. Rather, when the number of people walking on a bridge passes a threshold, the force of their collective footfalls pushes the bridge from side to side in sync with the bridge’s minute oscillations

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Researchers found that pedestrian bridges don’t become more unstable as more people walk over them. Rather, when the number of people walking on a bridge passes a threshold, the force of their collective footfalls pushes the bridge from side to side in sync with the bridge’s minute oscillations