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Rotation of the Earth
Intermediate
Earth's spin causes day and night and the equatorial bulge.
Earth spins once per sidereal day, ω ≈ 7.29×10⁻⁵ rad/s. It causes day and night, flattening, trade winds and Coriolis deflection.
Equator speed is about 465 m/s.
Earth's spin is slowly decreasing due to tides.
In more detail
The Earth rotates once per sidereal day, about 23 hours 56 minutes. Its angular momentum is conserved on large scales, and the rotation shapes winds, tides and the day-night cycle.
Real-world uses
- Satellite and rocket launches exploit Earth's rotation for extra speed.
- Weather patterns are shaped by the rotation of the Earth.
- The Earth's spin makes the equator bulge slightly, and its rotation sets the length of day and the pattern of winds.
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Frequently asked questions
Why is a day 24 hours and not exactly the rotation period?
Because Earth orbits the Sun, so it must rotate slightly more than once to bring the Sun back to the same position.
Is Earth's rotation slowing down?
Yes, very slowly, because of tidal friction from the Moon.
Why is the Earth's equator bulged?
Its spin produces a centrifugal effect that is largest at the equator, which slightly flattens the planet at the poles.
Related topics in Rotational Motion
Collisions in rotation · Precession of a gyroscope · Nutation · Tops and bicycles · Rotating frames · Euler's equations