In honor of the recent super moon, I’ve decided to write about how the tides work. I had never really considered the process before, and found it to be surprisingly complex. Or, at least, I was surprised it was more complex than just “the moon.”
I have to preface this post with these words: I am a molecular biologist by training. I am not an astrophysicist or nor am I an amateur anything-to-do-with-planets. This is my humble understanding along with some cartoons. Feel free to correct me!
There are two major players here ““ the Earth and the moon. The sun is important a little later on, but we’ll get to that.
First of all, the Earth and the moon are involved in an intricate dance. The moon’s gravity is constantly pulling on the Earth, which doesn’t do all that much to the Earth other than pull the Earth’s oceans toward the moon. This causes a bulge in the oceans on the side of the Earth facing the moon.
At the same time, there is another force working on the Earth’s oceans. This is an outward force called centrifugal force. Even though we like to think of the moon as orbiting our planet, both planets actually rotate around a common center of gravity. Centrifugal force pushes the water outward, away from the moon, resulting in a bulge of ocean water on the exact opposite side of the ocean water being pulled toward the moon.
We have two bulges in ocean water, where tides are high. The thinning of ocean water, at points opposite, are where the tide is low. This results in two high tides a day for most places on Earth, although there are exceptions.
The sun also exerts gravitational powers upon the oceans of Earth. This is why when the Earth, moon and sun line up and we see a new or full moon, the tides are bigger! More gravity is being exerted; larger tides occur!
This is relevant because the super moon of this weekend was at the perigee of the elliptical orbit; the point closest to Earth in 18 years. And because the moon was full, the sun was also adding some gravitational powers to the tides. According to NASA, however, the difference in the tides was only some 15 or so centimeters, so while the moon was gorgeous, the tides weren’t dangerous.
Unless you believe that the super moon was actually Gallifrey coming back.
Special thanks to Calisee, who asked me how to explain how tides worked, and when I said, “The moon,” pointed out that that couldn’t be all that was going on.
As ever, if you have questions or issues, feel free to email me at AskDorilysAboutScience@PersephoneMagazine.com!
http://www.youtube.com/watch?v=CTQ6ciHENgI – A guy explains tides with a cookie, a pickled onion and an orange.