Abstract

A: The Earth, Moon, and Sun circle each other in a free-fall dance, their orbits a delicate balance of mutual gravitational attraction and centrifugal force. One might think that in such free fall all the forces would be completely "used up", but this is not so. The left-over gravitational forces from the Sun and Moon produce tides that move the waters of Earth's oceans by dozens of feet and create changing stresses and displacements in the Earth's crust. These left-overs are called "tidal forces"