One of the most common misconceptions is that the regions at or near the equator are hotter than the poles because the equator is closer to the sun than other areas of the earth. Linked to this misconception is another misconception that Earth’s seasons are as a result of the distance of the Earth from the sun. However, the sun is so far away from the earth that it shines almost equally at the poles and equator. If the sun shines equally in almost all areas, why are regions around the equator hotter than areas around the poles? Below is an explanation of why equatorial regions are very hot, including direct vs indirect sunshine, the reflection of sunrays, and atmospheric differences.
The Amount of Sunshine Received at the Equator
While the sun shines almost equally in all parts of the earth, the equator is exposed to a high amount of direct sunlight than the poles. While the sun is directly overhead at the equator, it is slightly slanted at the poles. The earth is tilted 23.5 degrees on its axis and remains tilted throughout the year. Half the year the northern hemisphere is tilted away from the sun while the southern hemisphere is tilted towards the sun and vice versa in the other half of the year. Thus, the polar regions spend half the year pointed away from the sun. Thus, the sun rays cover a large area due to the tilt and also do not hit all the areas with the same angle and intensity. While the sun rays hit the poles at an angle, the same amount of sun rays hit the equator regions more directly and in a more concentrated manner.
So, if the same amount of light rays fall on two different surfaces. On one surface, the light rays are directly overhead and concentrated in a specific area while on the other surface the light rays reach the surface from a slightly slanted angle and spread over a larger area. The effect is that the area that directly receives light rays over a small area is likely to be hotter than the surface that receives light “indirectly” over a large area. The area that receives direct light rays is the equator while the other surface that receives light rays “indirectly” is the polar region.
Reflection of the Sun’s rays on the Earth’s surface
When the sun’s rays reach the earth, some of it is reflected back to the atmosphere and does not get to warm the area. The amount of rays reflected depend on the nature of the surface. Areas with snow reflect back up to 95% of the incoming sunshine. Regions around the equator absorb a lot of sun rays leading to warmer conditions, unlike the polar regions (the Arctic and Antarctica) which reflect a lot of sun rays due to the massive snow.
Difference in Atmosphere
The amount of sunlight absorbed and scattered while passing through the atmosphere depend on the nature and concentration of air molecules in the atmosphere. All other factors held constant, the sun’s path is longer in a higher latitude. The presence of more air molecules and particles result in greater absorption and scattering of sun rays. Thus, these places on high latitude receive less solar energy.
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