A diagram showing the different rotation axes.
The Earth's Rotation
The Earth is rotating around an axis
(called its rotational axis
). Some objects rotate about a
horizontal axis, like a rolling log. Some objects, such as a skater,
rotate about a vertical axis. The Earth's axis is tipped over about
23.5° from vertical.
How do we define up and down in space? What would "vertical" mean?
For the Earth, we can think of vertical as straight up and down with
respect to the plane in which the Earth orbits the Sun (called the ecliptic).
Earth's rotational axis points in the same direction relative to the stars, so that
the North Pole points towards the star Polaris. Think of the Earth as
a spinning top, tipped over to one side. Over very long time periods (thousands of years) the direction of Earth's axis slowly changes due to precession.
The Earth rotates around once in 24 hours - that's a rate of 1000
miles per hour!. The time it takes for the Earth to rotate completely
around once is what we call a day. It's Earth's rotation that gives
us night and day.
The combined effect of the Earth's tilt and its orbital motion result in the seasons.
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