Why Does Earth Have Seasons?

SEASONS

In the northern hemisphere in summer, the Sun rises in the northeast, stays high overhead at noon, and sets in the northwest. In the winter, the Sun rises in the southeast, stays low in the southern sky at noon, and sets in the southwest. Seasons are caused by the Earth’s tilt of rotational axis to the ecliptic and not by the Earth’s distance to the Sun. The Spring (Vernal) Equinox is the first day of spring (third week in March), when the Sun crosses the Celestial Equator the first time in the year. The Autumnal Equinox is the first day of Fall (third week of September), when the Sun crosses the Celestial Equator six months later. The Summer Solstice is the first day of summer (third week in June), the longest day of the year, and when the Sun is at its highest point in the ecliptic. The Winter Solstice is the first day of winter, the shortest day of the year, and when the Sun is at its lowest point in the ecliptic.

2012 Dates:

Vernal Equinox = March 20, 2012

Summer Solstice = June 20, 2012

Autumnal Equinox = September 22, 2012

Winter Solstice = December 21, 2012

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