Earth Rotation Day

Today, we think about the Earth’s movement: rotation means to turn, and revolution to go around. It wasn't always evident that these motions occurred.

Ptolemy postulated that the Earth was the center of the Universe and that the Sun revolved around our planet. Copernicus performed experiments that showed the opposite was true and published his results in 1543, months before his death. The printer added disclosures regarding the validity of the statements and suggested the information only aided astronomers. His book was banned by the Catholic church as heresy in 1616.

In 1632, Galileo agreed with the Heliocentric Model aided by the use of his telescope. He, too, was accused of heresy and placed under house arrest for the remainder of his life. It was not until 1758 that the Catholic Church decided it was not heretical to say the Earth rotates around the Sun.

Leon Foucault proved the theory of rotation with his famous pendulum experiment. You can view the Pendulum in the Paris Pantheon.

How fast does the Earth rotate in a “24-hour” day? A complete axial turn takes 23 hours and 56 minutes, but hold onto your hats: the diagram above notes the speeds relative to the location of your longitude. Why don’t we feel the Earth’s spin? It’s because we and our environment are all moving at the same constant speed.

The Earth’s rotation affects the weather by the Coriolis Effect: “the pattern of deflection taken by objects not firmly connected to the ground as they travel long distances around Earth.” This phenomenon causes global wind direction. The Trade Winds facilitated early marine explorers.

Is all of this science making you dizzy? I find it fascinating to recall basic facts I learned in school and investigate additional details.

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