Seasons and the Sun’s Location
Seasons occur on a planet or moon because the axis of rotation remains tilted in one direction during its orbit about its star; Earth about the Sun. The tilt is relative to the planet’s or satellite’s orbit. This tilt results in a planet or moon having Seasons. Earth’s axis is tilted about 23 1 2 °. And for comparison, the axis of Mars is tilted about 25°. Not all planets are tilted on their axis, for example Mercury’s tilt is 0°.
One of the results of Earth undergoing seasons is changes in day and night lengths. In the summer the days are longer and nights shorter. In the winter it is just the opposite.
Day and Night Lengths for Jacksonville, Florida; 2018
|Date||Season||Day Length Night Length|
|March 20||Vernal Equinox Start of Spring||12 hours 8 minutes 11 hours 52 minutes|
|June 21||Summer Solstice Start of Summer||14 hours 7 minutes 9 hours 53 minutes|
|September 22||Autumnal Equinox Start of Fall||12 hours 8 minutes 11 hours 52 minutes|
|December 21||Winter Solstice Start of Winter||10 hours 11 minutes 13 hours 49 minutes|
Seasonal Position of Sunrise and Sunsets
|Season||Position of Sunrise||Position of Sunset|
If you watch sunrise and sunset locations over a year, you will also note that the location of where the Sun rises and sets changes. As we orbit the Sun, the rising and setting points are further north in the summer and further south in the winter. There is a variable here: your location on Earth. For example, if you are at far northern or southern latitudes, you will experience extreme day and night lengths, depending on the seasons. And, for those north of the Arctic Circle or south of the Antarctic Circle, you will experience some days with no nights, or some nights with no days. (1)