Solar radiation is not distributed equally across the Earth because of Earth’s tilt, rotation, and revolution around the sun. At the equator, the sun is nearly straight overhead most of the year, so most of the equatorial region is hot. In the polar regions, the opposite is true. Poleward from the equator, the climate gradually shifts from hot to cold. In between, is the temperate zones, which include the United States. The tilt (about 23.5 degrees from the perpendicular) remains the same all year but changes relative to the sun. This is the primary cause of weather and climate.
During the Northern Hemisphere summer, the North Pole tilts toward the sun, allowing the region to be in constant daylight, while the South Pole is in continuous darkness. This is reversed during the Northern Hemisphere winter.
Use the slider to see how Earth is positioned in relation to the sun at different times of the year.
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