As the Earth rotates on its axis, one side of it face the Sun, thus giving that side daylight. On the other hand, it is night on the shaded side. As the Earth continues to turn, the shaded side moves into the Sun's light, and the sunlit side turns away from the light. It takes 24 hours for the Earth to make one complete turn on its axis, and our clock is based on this principle.
In the 1940s, people discovered than the Earth speeds up and slows down a little as it spins, although the reason for these changes is not fully understood. We have now developed atomic clocks that can measure time exactly.
In the 1940s, people discovered than the Earth speeds up and slows down a little as it spins, although the reason for these changes is not fully understood. We have now developed atomic clocks that can measure time exactly.
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