How the Moon Really Causes Tides

Estuaries are strongly influenced by tidal forces. As an Estuarian who spends as much time as possible in landscapes shaped by tides, I pay attention to tides, think about them, and want to learn more.

The standard explanation for why tides occur, the one given in science textbooks and the like, always seemed wrong. As a kid I couldn’t figure out why high tides occur on two the sides of the earth: the side facing the moon and on the side opposite the moon. Later, I understood the standard explanation for this. But I still questioned how the moon’s gravity could possibly produce such powerful tidal forces on earth.

How could the moon’s gravity—something so tiny that I cannot feel its pull on my body—move so much water into and out of, say, Tomales Bay twice daily? Why didn’t tides occur on large lakes?

Turns out that the common explanation of how tides work is wrong.

This video provides a much more satisfying explanation.


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