“…This was one of the first observations of the phenomenon of the coupled harmonic oscillators, which have many applications in physics [89,16,[18][19][20]47,93,5,99], biology and chemistry [93,60,63,64,100,104]. In engineering very spectacular was synchronization of pedestrians on Millennium bridge [1,19,36,37,42,81,84,86]. Huygens originally believed the synchronization occurs due to air currents shared between two pendula, but later after performing several simple tests he dismissed this and attributed the sympathetic motion of pendula to imperceptible movement in the beam from which both pendula were suspended.…”