The rhythms of the sea: a primer on tides
West Sands Beach near St. Andrews, Scotland, where the tidal range (the difference between high tide and low tide) can be up to 4 meters. Few natural phenomena capture the imagination and, at the same time, affect daily experience as much as the oceanic tides. With their daily rhythm, tides may have even shaped the evolution of life itself: it has been suggested that tides played a role in the transition from marine to land animals at the end of the Devonian period [1]. Understanding tides allows us to fully appreciate a hidden clockwork that connects celestial mechanics with the ebb and flow of the sea, and its impact on life on Earth. Tides follow highly regular patterns, as is immediately obvious to anyone who lives near a coastal area with a tidal range of the order of meters (as opposed to the puny tens of cm in my Mediterranean hometown!). In this post I will discuss how the most readily observable periodicities in the rise and fall o...