4. WHAT CAUSES THE SEASONS?
The cycle of seasons is caused by Earth's tilt toward the sun. (Image credit:
KajaNi via Getty Images)(opens in new tab)
The cycle of seasons is caused by Earth's tilt toward the sun. The planet
rotates around an (invisible) axis. At different times during the year, the northern
or southern axis is closer to the sun. During these times, the hemisphere tipped
toward the star
experiences summer, while the hemisphere tilted away from the sun
experiences winter, according to the National Oceanic and Atmospheric
Administration (NOAA)(opens in new tab).
At other locations in Earth's annual journey, the axis is not tilted toward or
away from the sun.
During these times of the year, the hemispheres experience
spring and autumn.
The astronomical definition of the seasons relates to specific points in Earth's
trip around the sun. The summer and winter solstice, the longest and shortest day
of the year, occurs when Earth's axis is either closest or farthest from the sun. The
summer solstice in the Northern Hemisphere occurs around June 21, the same day
as the winter solstice in the Southern Hemisphere, according to NOAA. The
south's summer solstice occurs around December 21, the winter solstice for the
north. In both hemispheres, the summer solstice marks the first day of
astronomical
summer, while the winter solstice is considered the first day of astronomical
winter.
Equinoxes are another significant day during Earth's journey around the sun.
On these days, the planet's axis is pointed parallel to the sun, rather than toward or
away from it. Day and night during the equinoxes are supposed to be close to
equal. The spring, or vernal, equinox for the northern
hemisphere takes place
around March 20, the same day as the south's autumnal equinox. The vernal
equinox in the southern hemisphere occurs around September 20, when people in
the north celebrate the autumnal equinox. The vernal equinox marks the first day
of astronomical spring for a hemisphere, while the autumnal equinox ushers in the
first day of fall.
But changes in the weather often precede these significant points. The
meteorological seasons focus on these changes, fitting
the seasons to the three
months that best usher them in. December to February marks meteorological
winter in the Northern Hemisphere and meteorological summer in the southern.
March, April, and May are lauded as spring or autumn, depending on the location,
while June through August are the months of summer for the north and winter for
the south. September, October, and November conclude the cycle, ushering in fall
in northern regions and spring in southern, according to NOAA.
The seasons can bring a wide variety to the year for those locations that
experience them in full. The weather in each one may
allow people to engage in
activities that they cannot perform in others — skiing in the winter, swimming in
the summer. Each season brings with it its own potential dangers, but also its own
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