Fall/autumn: when does it start? (Northern Hemisphere)

in #stem2 years ago (edited)

Well kids do ask a lot of questions. Some are easy to answer, others aren't. On some questions you have no clue at all what the answer would be, but are intriged what the correct answer is!

A few days ago, we were sitting in the car and the weather news was on the radio. There were talking about the weather in the beginning of the fall! So one of the kids asked why they were talking about the fall already because that only starts at the 21ste of September!


I do know that there is a difference between the start date for the fall for Meteorologists and as regular people!
So that was easy to explain. But of course every answer is followed by another question. So the next question was, why is there a difference! And that is when I didn't know the correct answer!

So when back at home I decided to check why and to my surprise all school books are also wrong! Maybe they did teach me how it should be and why it is different but I can't remember! Getting old I guess!

Astronomical vs meteorological seasons!

This is the explanation for the nothern hemisphere, in the southern hemisphere it is the other way around!
The astornimocal season are the season we use, they do have a fixed date on the calender! Like the term explains it is related with the position of our beloved blue planet with the sun.
Normally fall really start when the sun shines directly on the equator. This is the time of year that day and night have an equal length! From that moment on, the nights will last longer than the day, slowly increasing to its max. The day when the duration of the night is at his max is the start of winter.Days start to fight back and when both have again an equal length, spring will start! When we do have the longest day of the year the summer starts! At the start of the summer the nights are starting to fight back!

If we look at the past and comming year, fall hasn't started on the 21ste of September

201622 September
201722 September
201823 September
201923 September
202022 September
202122 September
202223 September

Have you noticed that in none of these year, the fall/autumn did start on the 21st of September? So why do we think that fall start at the 21st?

During our Gregorian Calendar fall have never started on the 21st, nor is it the average!
The best reason I can think off is that the above is not easy to teach kids at kinder garden! So a date has been choosen and more or less carved in stone!


What a word to type!
Well here the definition of the season is more straight on! Each season lasts exact 3 months on the Gregorian calendar. This is really carved in stone since 1780. These dates were decided during by the Societas Meteorologica Palatina, which was an early international organization for meteorology. Probably this also their most famous decision because it became defunt in 1795.
The idea behind it was that each season would have the same duration for all years, which makes it much easier to compare statistics with each other! There are no scientistic evidences for this! It makes things just easier, just like the kids here in Belgium do learn at kinder garden that fall start on the 21st!
Of course a lap year can have some influence on the days that the winter counts!

Well I now know enough to give my kids are well funded answer!
If they are still interested :)




This is an interesting read. From a country with only one season year round, I would never think of that question. Your kids make your smarter. =)

They indeed do!
Happy with our 4 seasons. All of them do have their charm!

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