Time and Tide, Part One

Let’s take a look at the physics behind our tides using an iron barbell to demonstrate some of the principles that affect them. The better we understand these concepts, the better chance we have of correctly estimating our local tides during a voyage, should we need to.

Imagine, for a moment, that I have a barbell—two iron balls of equal mass held together by a steel bar. If I want to balance this barbell on a fulcrum, I have to place the fulcrum at the center of the mass between the two iron balls. Now, if I am able to throw this barbell so that it tumbles end over end, the point around which the balls will pivot is the same point on which I had positioned my fulcrum (). This point on my steel