Goodbye summer, hello autumn!
Today's September 23rd is the beginning of the autumnal calendar. For the meteorologists, he already started on 1 September. BILD explains the difference and why we have seasons at all.
The meteorological start of autumn on the 1st of September has a simple reason: With this "smooth" date, the weather experts can better compare the months in the statistics.  When does the beginning of the calendar begin?
But autumn actually begins on September 23, 2015 at 8.21 am: astronomers determine this time according to the position of the sun. When it is vertical above the equator, the new season begins in the northern hemisphere of the world.
The beginning and the beginning of the spring have one thing in common: day and night are the same length. In the following weeks until the beginning of winter on the 22nd of December the days become shorter and the nights longer.
Why are there seasons?
Our earth revolves around the sun ̵
This also changes the position of the sun: when it is high above the horizon, the beginning of summer, when the sun is low, begins the winter.
On the 23rd of September the sun passes the celestial equator in a southerly direction. At 9.50 clock summer time, it passes the autumn point, the autumnal equinox occurs. This means: Our nights are longer than the days again. On December 22, the sun reaches its lowest point in winter at the winter point.
By the way: While the autumn on the northern hemisphere begins on the 23rd of September in the southern hemisphere there is a beginning of spring in the southern hemisphere.
With a Google Doodle on September 23, the search engine celebrates the beginning of the autumn with a typical orange-brown autumn foliage.