The earth’s atmosphere also refracts the sun’s light over the horizon when it has just set or not yet risen. As a result, the length of daylight today is still twelve hours and thirteen minutes.
The seasons change because the Earth’s axis of rotation is tilted by a good 23 degrees. As a result, over the course of a year, sometimes the northern and sometimes the southern hemisphere points towards the sun. Tomorrow we will experience exactly the transition.
Celestial mechanics provide consolation
If the axis of rotation of our planet were perpendicular to the earth’s orbit, we wouldn’t have any seasons – day and night would always be twelve hours long. This is only the case on the oblique Earth at the equator. There all the stars rise and set vertically – and all objects are twelve hours above and below the horizon: the sun as well as Jupiter, Sirius or other stars.
For those who dread the colder and darker season, celestial mechanics has a consolation: from the beginning of October our earth is closer to the sun than average – in order to escape the stronger gravitational pull of the sun, the earth moves faster in its orbit .
This has consequences for the length of the seasons: autumn and winter are over a week shorter than spring and summer.