Lesson 2: Energy Angles

What causes the average temperatures on Earth near the equator to be higher than the average temperatures on Earth far from the equator?

Temperatures on Earth are generally higher (warmer) closer to the equator and lower (cooler) toward the poles. The patterns seen on Earth related to varying temperatures are caused by uneven heating of Earth’s surface. Earth’s surface heats unevenly because the Sun’s light (solar radiation and energy) hits different parts of the planet either more directly or less directly. When light hits a surface straight on (or perpendicular to it), the energy is more concentrated over a smaller area. When light hits a surface less directly (at a low angle), the energy is more spread out. The Sun’s light shines most directly the graph paper). When the Sun’s light hits at a less-direct angle toward the poles, it is more spread out and does not provide as much heat per unit area. Because Earth is a sphere, sunlight hits the curved surface more directly closer to the equator and less directly as you move closer to the poles. Solar radiation is most direct at or close to the equator and thus produces higher average temperatures. As one moves farther from the equator and closer to the poles, the sunlight is less direct. Because of the less-direct angles of sunlight the farther you are from the equator, solar radiation is less intense and therefore the average temperatures are lower. The angle of the Sun’s light affects the heating of Earth’s surface. When the angle of sunlight is direct, the sunlight is more intense and Earth’s surface will get warmer. When sunlight strikes Earth’s surface less directly—when we move from the equator to the poles (increasing latitude)—then the Sun’s light is less concentrated and the surface does not warm as much. Temperatures vary in the Northern and Southern Hemispheres at different times of the year.

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