The Reason for the Seasons
Because the Earth’s axis is tilted (23.5o), rays of sunlight are less direct and
more slanted during winter. This causes differences in the number of hours
of daylight and the temperature in the seasons. The tilt of the Earth also
causes the Sun to change in altitude throughout the year. It reaches its
highest noon-day altitude on June 21st, (summer solstice) and its lowest
noon-day altitude on December 21st (winter solstice). While proceeding
from one extreme to the other, the Sun passes through a mid-way point
twice a year. These are the two equinoxes: March 21st (spring) and
September 22nd (fall). The Sun is at varying heights throughout the year.
Because of this difference in altitude, the Sun’s rays strike the Earth’s
surface at vary angles during the year helping create the seasons. The tilt
of the Earth’s axis also causes the number of daylight hours to vary during
the year. In the summer the sun rises well to the northeast around 5:00 am
and doesn’t set in the northwest until around 10:00 pm. Combine this with
the Sun’s maximum altitude in summer and it’s easy to see why summer
days are warmer. During the long summer days, the Sun has a greater
opportunity to warm the Earth. In winter, the Sun just begins to warm the
Earth each day when it begins its decent into the southwest to set in the
late afternoon. The winter sun never has a chance!