Article
Tides Are Stranger Than You Think
Two bulges, a slow goodbye, and days that used to be shorter.
The Moon does not simply pull the ocean toward it. It stretches the whole Earth — water, rock, and all — into a slight oval, which is why there are two tidal bulges and most coasts see two high tides a day, not one.
The stranger part: the bulges run slightly ahead of the Moon, because Earth rotates faster than the Moon orbits. That offset drags the Moon forward, boosting it into a higher orbit by about 3.8 centimeters a year, while braking Earth's spin. Days are getting longer; the Moon is leaving, slowly. Coral growth rings record that a Devonian day was under 22 hours.
Photo: Share Bear (dmahalin@gmail.com), via Wikimedia Commons (Public domain).