14.4 NOTES
What are the solstices and equinoxes?
Define solstice and equinox
During the year, the distance between Earth and the Sun changes. Earth is at
perihelion, or closest to the Sun, in early January. They are about 147 million
kilometers apart. The Northern hemisphere has winter.
In early July, Earth is at aphelion, or its farthest point from the Sun. This distance
is about 152 million kilometers. Yet, this is summer in the Northern hemisphere.
The beginning of the summer and winter seasons is marked by a day called a
solstice, meaning “sun stop”.
The first day of summer in the Northern hemisphere is on or about June 21st. The
Sun seems to travel at its highest path across the sky. This day is called summer
solstice. Earth is very close to aphelion. The North Pole has 24 hours of daylight.
At the same time, the South Pole points away from the Sun, and has 24 hours of
darkness. Winter begins on this day in the Southern hemisphere.
The first day of winter in the Northern hemisphere is on or about December 21st.
This day is called winter solstice. Earth is very close to perihelion. The North Pole
points away from the Sun. The Sun seems to follow its lowest path in the sky. On
this day, the South Pole has 24 hours of daylight.
There are two times when the Sun is directly over the equator at solar noon.
These are the equinoxes, which mark the beginning of spring and fall. The spring
equinox is on or about March 21st, and the fall or autumnal equinox is on or
around September 21st. During these two days, there are 12 hours of darkness
and 12 hours of daylight everywhere on Earth.