Synchrony

Stephen Strogatz has been working in the area of synchrony. It studies the way complex systems synchronise their actions to enable new levels of co-ordinated complex behaviour. Fireflies in their thousands are known to be able to co-ordinate the flashing of their tails, so they all flash rhythmically in unison. He found that when they start off some flash faster and some slower. Those flashing slower became aware that they were flashing slower and sped up and the faster slowed down until the whole group flashed in unison with the rate determined only by the interactions of all the fireflies. It is a like a small group of friends running together. They must find a pace they are all comfortable with to run together, each adapting their individual rates to fit an overall pace.

Similar dynamics were in pay in an audience clapping after a fine performance. Sometimes the clapping will spontaneously synchronise with the whole audience clapping together in unison. It can then slip out of synchrony and back in again.

The neurons in the heart controlling the heartbeat and the small world network of neurons holding our short term memory in our brain operate through synchrony.  

 In 1665 Christiaan Huygens observed that two pendulum clocks in the same room would line up the swinging of the pendulums to the same rhythm. It turns out that the very faint rhythm transmitted through the floorboards was enough to bring the two clocks into synchrony.

When the millennium bridge was opened in London, the crowds of people all came onto the bridge. As they did their footsteps moved into synchrony and the frequency of all those footsteps made the bridge swing so dangerously it had to be closed until they could discover why the bridge had swung the way it did.

Our body has a number of rhythms controlling the many functions that must be integrated together. We have a circadian rhythm which is round about a one day cycle. It is not exact however, but is reset each day. It turns out that our body temperature runs in roughly 12 hour cycles and cycles of wakefulness and tiredness are linked, so we have low temperatures and around 2am and 2pm, when we are more likely to be sleepy and at 10am and 10pm we are alert. Errors in places like nuclear power plants are more likely to occur around 2am. Our body clocks are operated by thousands of neurons operating in synchrony rather than any “clock” as such.

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