The March and September equinoxes At the two equinoxes, Earth’s tilt is neither toward nor away from the Sun. As a result, the Sun’s declination is at the equator, meaning its rays fall directly there. The circle of illumination passes through the poles, resulting in near-equal days and nights everywhere on Earth, including the North and South Poles, as Figure 2 shows.
Figure 2. Sunlight at the Equinoxes
North
Suns rays
At noon on the Northern
Hemispheres vernal
(spring) equinox in
March and autumnal
equinox in September,
the
On the March equinox, which occurs on March 20 or 21, the Northern Hemisphere experiences spring and the Southern Hemisphere has autumn. On the September equinox, which occurs on September 22 or 23, the reverse is true.
After the spring equinox, in either hemisphere, days grow longer until reaching their maximum at the summer solstice. Then, they begin to shorten again until the autumnal equinox when daylength once again is equal to the length of the night. Days continue to shorten after this event until they are at their shortest at the winter solstice.
Which of the following are true of equinoxes?
Select the three that apply.
12-hour daylength at all latitudes
Midnight Sun or constant light at the North Pole during the March equinox
Solar declination at the equator
Daylength decreases after autumnal equinox
Solar declination at the Tropic of Cancer