How the Sun Warms the Earth
If a people preferred to live in warm weather all year long, where would they go? Or if they liked cold weather, where would they go? Making that decision depends on the angle at which the sun hits the earth. The sun warms the earth's surface which in turn transmits heat to the air above it. The angle that the sun hits the earth determines the amount of heat produced.
The sun's path is high overhead and at its hottest at midday. It shines down upon the areas around the equator at this time. At the same time the areas around the North and South Poles are coldest because they are further away at midday and the angles of the sun is different than the angle that hits around the equator. The lower the sun's angle the weaker the sun heats the earth.
The angle at which sunlight strikes the earth's surface is called the angle of insolation. Insolation is short for incoming solar radiation. It means the amount of the sun's energy that reaches earth at a given place and time. The amount of warming depends on the angle of insolation. The angle of insolation is always smaller near the North and South Poles which results in colder temperatures. On the other hand, the angle of insolation near the equator is greater and creates warmer temperatures. That means while it is freezing cold in one area of the earth it is hot in another.
What affects insolation? In the morning the sun is close to the horizon and at midday it is at its highest in the sky. After midday the sun lowers and the angle creates less heat. Measuring the angle of insolation is difficult because light rays are not easy to see. Therefore, the way to measure the angle is by measuring the shadows created by light rays. The shorter the shadow is, the more direct the angle of the light ray. As a result, the hotter the temperature is. The longer the shadow is, the more angle there is and the colder the temperature.
Why do some things get hotter than others? For example, dark colors get hotter than light colors in the same temperature. That is why dark asphalt roads get so hot in sunlight. Dark soils and rocks also get very hot. White sand and light colored rocks do not get as hot. The dark colors absorb the heat from the sun while light color reflects the heat.
The texture of a surface also determines its temperature. Texture is how smooth or rough a surface is. Rough textures cause light to bounce around at many angles. Each time a little more energy is absorbed by the surface. Therefore, rough surfaces tend to get hotter than smooth surfaces. The angles create heat.
If a person wants to live in a hotter climate, he or she would need to move closer to the equator because the sun's angle is at its highest closer to the equator and creates the most heat. On the other hand, if people want to live in a colder climate they need to move closer to the North or South Poles because while the sun is at its highest the Poles are further away and the angle of the sun is at its greatest. Angles create heat. The lower the angle is, the hotter the temperature will be. The higher the angle is, the colder the temperature will be. It is the angle of insolation that must be measured to determine the hotter or colder areas to live.
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