This animation demonstrates very simply how different elements at different heights, let off energy that we see as different colors.
Click on image for full size

Axis Tilt

When we talk about the movement of a planet, we talk about its rotation (spinning around its internal axis) and revolution (revolving around the Sun). Axis tilt occurs when a planet rotates around an axis that is tilted relative to the plane of its revolution around a larger object. Put simply, that means that as the planet revolves around the Sun, it is tilted.

The Earth is tilted by 23.5 degrees, which means that sometimes the northern hemisphere is tilted toward the Sun and sometimes it is tilted away from the Sun. This tilt of a planet is what gives us seasons.

Not all the planets have the same amount of tilt. Jupiter, for instance, has almost no tilt (3 degrees), while Venus has almost 180 degrees of tilt, which means that itís spinning upside-down (at least relative to our definition of up). Uranus has a tilt of almost 90 degrees, which means that this planet is spinning on its side!

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