Despite being set off at different times and independent motion, within a period the pendulum synchronised with each other. Subsequent experiments duplicated the same phenomena.
Huygens at the time described the effect as ‘odd sympathy’. On further study of this seemingly unrelated behavioural correspondence, it has become know as ‘Entrainment’.
Entrainment describes the tendency for one entity to resonate synchronously with another in response to a dominant frequency of vibration. On further exploration, entrainment is an integral natural phenomena which can be observed at all levels of our physical world and in the behaviour of its inhabitants.
And we have to begin at a quantum physics level to understand how this works. Everything in the universe is made up of particles or waves that vibrate like strings at different frequencies. Quantum physicists describe everything in the universe as vibrating. Particles resonate together to create a united front that is matter. Within this atomic vibrational chorus resonating particles will communicate with, and influence each other. The result is an intelligent synchronisation of behaviour across entities.
But why is this beneficial?
According to further scientific study, entrainment exists for the purpose of conserving energy. This phenomena appears because it takes less energy to work in harmony with surrounding elements than to work against them. And whilst the behaviour begins at a particle level, examples can be far more sophisticated from the biological and pharmacological, to the psychological and sociological.
At a higher level further up the existence chain, plants and animals become synchronised due to such diverse stimuli as light, sound, temperature and even social activity. These environmental cues are called zeitgebers (German for timegiver).
Light is the easiest cue to observe. We are entrained to a 24-hour light-dark cycle provided by the precise daily signal caused by the rotation of the Earth.
Subtle fluctuations in temperature can effect behaviour in animal groups. Lizards are so sensitive to this cue that they can entrain to temperature cycles with a change of less than 1°C.
Social cues from other organisms in the same environment can also act as zeitgebers. Human volunteers kept in constant dark with 24-hour feeding and sleep patterns stay entrained to the 24-hour cycle. Submariners entrain to an 18 hour day as they tend to operate a three x six hour watch system.
But there are far more sophisticated and wonderful examples of entrainment in nature. Animals regularly synchronise their breeding cycles and sleep patterns.
Let’s take our daily menace, the humble mosquito. Mosquitos alter their wing-beat frequency in response to the flight tone of others nearby. Within seconds a scourge of mosquitos will have closely matching wing-beat frequencies, if not completely synchronised.
Fireflies will flash their light emissions at the same time. This beautiful phenomena was described in 1935 by Hugh M. Smith, a biologist from Washington USA, in the journal Science.
“Imagine a tenth of a mile of river front with an unbroken line of Sonnerati trees with fireflies on every leaf flashing in synchronism, the trees at the ends of the line acting in perfect union with those around. Between flashes the trees are in complete darkness.”
Fish and flocks of birds have highly synchronised movements in an attempt to reduce energy expenditure. In addition to this Dr Matz Larsson PhD believes that synchronisation of group movements in nature may improve hearing perception. Sounds produced due to movement seem to be used by schooling fish as an aid to staying in formation and avoiding collisions. Bird and bat flocks are also noted to display the same behaviour, enabling them to hear predators more easily and to co-ordinate their flight patterns.
Higher up the food chain still, entrainment continues to weave its magic spell. Women who spend a lot of time together observe a synchronisation of their menstrual cycles. Close social groups have also been observed to dress and think similarly. Entrainment is at work when people tend to assimilate the mood of the surrounding environment. In a room full of unknown people laughing, the entrants spirits will inevitably lift due to social homogenisation.
It has also been recorded that two people having a good conversation together can elicit synchronous oscillations in their brain waves.
The beat of a drum has a similar effect, and most notably why it has been used as a device for unison since the early history of social man. By listening to a steady drum beat our brain wave patterns change from beta to alpha waves. The effect is to sedate the left hemisphere of the brain, which would normally get distracted by external events, and this aids humans to connect with the more intuitive side of the brain.
People moving together in a busy space will begin to walk in time with each other. And this behaviour has even highlighted some amusing examples of architectural flaws.
When the London Millennium Footbridge (a steel suspension bridge) opened in 2000, the entrainment of people walking in step sent a ripple of resonant waves through the structure that made it sway so significantly that it resulted in expensive restructuring to prevent its sympathetic movement that was aligned with its passengers.
Just think of the possibilities. If we all take our beach spades down to the Chalong circle, perhaps those dormant industrial excavators will whir back into life and start digging alongside us.