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We wouldn't have seasons here on Earth if not for the planet's 23.5 degree axial tilt.

Axial tilt is also known as obliquity.

Earth's obliquity and its relationship with the sun give us two solstice points and two equinox points.

As we orbit through each solstice and equinox, the amount and angle of daylight change.

A 12-month sequence of Landsat imagery shows how much each month can differ, especially away from the equator.

In extreme northern latitudes, sunlight during the winter solstice is so limited that daytime Landsat imagery is not available, while Antarctica receives long hours of daylight in the extreme southern latitudes.

This multi-path swath of Landsat imagery in the Western Hemisphere shows the big picture. It contains only cloudy Landsat images, which are brighter and help show the change from north to south as the seasonal angle of the sun changes.

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