Lesson 6: Use and Apply

Why are some places on Earth hotter than others at different times of the year? How can we use what we have learned to answer our Unit Central Question?

Some places on Earth are hotter than others at different times of the year because of variations that result from the tilt of Earth on its axis, the angle of the Sun’s light (solar radiation) striking Earth’s surface, and Earth’s orbit around the Sun. The angle of the Sun’s light, and thus the intensity of the solar radiation, depends on how far north or south of the equator a place is, its latitude. The angle and intensity of the Sun’s light also varies by time of year. For example, when a hemisphere is tilted away from the Sun during its winter, the Sun’s rays strike at a less direct angle which spreads the sunlight over a larger area and results in less heating and cooler temperatures. When a hemisphere is tilted toward the Sun during its summer, the solar radiation strikes Earth more directly, resulting in more concentrated energy and thus more heating of Earth’s surface and higher temperatures. Because Earth’s tilt is consistent throughout its orbit, summer in the Northern Hemisphere occurs in June–August and winter in December–February. The Southern Hemisphere is opposite, experiencing summer during December–February and winter in June– August. Earth is heated unevenly, causing some places to be hotter than others due to many measurable factors, including consistent tilt, orbit, and angle of the Sun’s energy striking the surface of Earth.

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