Why do fireflies flash synchronously?

In the wild, fireflies will always flash spontaneously in unison. When a metronome is placed on a piece of green cardboard, after a while, the rhythms of several metronomes become exactly the same. In a theater, the audience claps at the same frequency without anyone asking them to do so. These seemingly common synchronization phenomena are

Scientists have studied it for more than three hundred years, and even now they have not been able to fully unravel the reason for their synchronization.

In 1656, in order to help sailors figure out their position on the earth, the famous Dutch physicist Christian Huygens invented the world's first working pendulum clock, which reduced the clock's error of fifteen minutes a day to ten to fifteen seconds.

Sailors at the time had already mastered how to use the angle between the sun and the sea level to determine the latitude of the ship, and the accuracy was determined by the time difference between the departure point and the local time. A one-hour time difference is equivalent to a change of 15 degrees of latitude.

In February 1665, Huygens, who was ill at home, conducted an experiment in which he placed a wooden beam between two chairs.

Then he hung two pendulum clocks on the wooden beams to simulate the swing of two clocks hanging on the cabin during the voyage. In this way, he stared at the pendulums for several hours. Then he was surprised to find that no matter what the initial positions of the two pendulums were, after about thirty minutes, the two pendulums would always swing at the same frequency, and their phases would always be in opposite positions.

At first, Huygens thought that this strange induction of the pendulums must be caused by air currents between the pendulums, so he placed a large board between the pendulums to prevent the propagation of air currents. But after thirty minutes, the pendulums were still synchronized, so he separated the two clocks from the wooden beam and tested them again. This time their time synchronization was gone, but when he put them back on the beam, the synchronization returned.

Huygens wrote a letter to the Royal Society of London about the observed synchronization phenomenon, but it did not attract much attention at the time.

Huygens was the first to observe this spontaneous synchronization in inanimate objects. Although he described the phenomenon qualitatively,

But it was not until 2015 that scientists figured out why the pendulums were synchronized. Professor Hank Niedermeyer of Eindhoven University of Technology in the Netherlands conducted numerical simulations and theoretical analysis and concluded that the pendulums were synchronized because the ticking sound of the pendulums caused the table to vibrate, thereby achieving energy exchange between the two pendulums and thus achieving synchronization.

At night, fireflies flash synchronously, even though each one has its own specific frequency.

The reason is that the intensity of their mutual coupling is strong enough that hundreds, thousands, or even tens of thousands of them can flash together at the same time. Scientists have done a good simulation. In the model, a firefly is only affected by its neighbors. If it sees a flash nearby, it will push its own flash time forward a little.

After a while, something magical happened. Even though the interactions were small and close, over time, almost all of the fireflies eventually flashed in unison, and the theater applauded in unison.

The second law of thermodynamics tells us that everything in the universe tends toward disorder, and in complex systems, disorder is the norm.

However, these common phenomena in daily life are gradually becoming orderly and not affected by disorder. At present, studying the synchronization behavior in various practical complex systems has become one of the hot issues of common concern in different disciplines.