Reasons for Seasons

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Reasons for Seasons Some students think that the seasons are due to the distance of the Earth from the Sun since objects closer to a heat source tend to be hotter. This notion is based on the incorrect belief that the Earth’s orbit is an exaggerated ellipse. Since the Earth’s orbit is nearly circular, its distance from the Sun is fairly constant. Lambert indicates that students may also misunderstand the orientation of the Earth’s axis. Some students believe that the Earth’s tilt changes in degree as the seasons change and that the axis points in different directions as the Earth orbits the Sun. In reality the Earth’s axis is always tilted at 23.5 degrees and the North Pole always points toward Polaris (Lambert, 2010). Most of the planets in the solar system have nearly circular orbits, much like Earth. The orbits do, however, have an elongated shape. The orbits of Mercury and Pluto are very elongated whereas the orbits of the other planets are almost circular (Nelson, 2005). There is a point along each orbit, called the perigee, where the planet is closest to the center of the Sun, and a point, called the apogee, at which each planet is the furthest from the center of the Sun (Lambert, 2010). Recall that the seasons are the result of a planet’s tilt, not its proximity to the Sun. As such, when the Earth is closest to the Sun at the perigee, the Northern hemisphere is experiencing summer and the Southern hemisphere is experiencing winter. But the proximity of the Earth to the Sun does not influence the seasons. Unique conditions contribute to the seasons of the planets in our solar system. The planets Mars, Saturn and Neptune all have a very similar tilt to that of Earth, so they experience similar seasons, in relation to their orbits, as the Earth does. Since these planets have larger orbits and the planets themselves are further from the Sun than is the Earth,

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