What Happens when a bridge Wobbles?

When the millennium bridge first opened, much to the amusement of bewildered onlookers, the bridge began to wobble. The first pedestrians in order to compensate for this unexpected vibration found themselves walking in step magnifying the wave. The effect is called entrainment and physicists and engineers know it well.

The Tacoma bridge in the US was famously filmed tearing itself apart when high winds caused the bridge to resonate at it’s natural frequency.  An occurrence that undoubtedly is a bridge engineer’s worse nightmare.

An example of this entrainment effect is beautiful illustrated with a metronome experiment – a row of metronomes set at differing bpms are place on top of an unstable surface which has the ability to ‘wobble’. It in order to stabilise the two oscillating systems (the metronomes is one and the wobbly surface is the other) assume the same the period.

This process occurs everywhere in our natural world. If we consider that most things are oscillating and vibratory systems of some kind it makes senses. But for me where it really gets wild is in human communication. We entrain to each other in deep conversation. This is rapport. Subconscious physiological rhythms begin to assume the same frequency in people who are getting on – heart beats synchronise, blinking patterns match, breathing rates mirror. It can be seen in the example of a close group of women whose menstrual cycles become the same. In chronobiology the most common example of entrainment is of the circadian rhythms to the daily light-dark cycles of the environment.

Essentially we are vibrating entities that pick up other people’s and our environments frequencies…send out the good vibes people.