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The Times They Are a-Changin'

Radiolab

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The Dance of Time: Earth's Changing Days

The concept of a day on Earth, defined as a complete rotation of the planet relative to the sun, has evolved significantly over time. Initially, Earth completed its rotations more quickly, resulting in a year comprising 450 days. As the planet continued to develop, the introduction of the moon altered this dynamic. The moon's orbit around Earth progresses at a slower pace than Earth's spin, creating a gravitational tug that affects Earth's rotation speed. This interaction has led to a gradual decline in Earth's spin, lengthening our days over billions of years. Currently, Earth's rotation slows by approximately 1.7 milliseconds each century, illustrating a continuous and measurable change in the duration of a day as a result of this cosmic dance.

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