June 1, 2009
Have you ever heard of an Earth tide? Like the oceans, the solid crust of Earth also moves to a lunar rhythm. While the seas rise and fall by a worldwide average of three feet daily, the ground oscillates by about 8 inches (scientists measure this with satellites). This mutation is not merely a surface phenomenon; the entire planet undergoes constant and complex rhythmic deformations.
What’s remarkable is that they’re so small. It’s evidence that our planet is incredibly well–built. To have a body as massive and as near as the Moon, and to have our planet changed so little by its presence, means that Earth is one of the solar system’s construction success stories.
Down beyond the haven the tide comes with a shout.
–William Sharp, Scottish writer (1855-1905)