Ocean Tides and the Earth's Rotation (2001)

Ocean Tides and the Earth's Rotation An Introductory Discussion Courtesy of the Tides affect the earth's rotation in two sharply contrasting ways. One way, caused by tidal friction, produces an extremely slow secular change in rotation. The other way, caused by the continual movements of the tides about the planet, produces very small but very rapid changes in rotation. These rapid changes occur at exactly the same periods as the tides themselves -- half-daily, daily, etc. (The IERS Special Bureau for Tides is concerned primarily with the rapid changes, but some of our data have implications for the secular changes.) Secular Tidal Braking of Earth Rotation The secular change in the planet's rotation is a classical topic in geophysics. It goes back some 300 years to when Sir Edmond Halley first hypothesized that the moon was accelerating in its orbit. Most of Halley's lunar acceleration was only apparent. It was actually the earth's rotation slowing down, making the moon appear to a ... Read full article.