why December 21 is the shortest day of the year

See my news
Follow News

That's it. Even though meteorological winter began on December 1, we officially enter the winter period this Saturday, December 21, 2024. It is the winter solstice, the shortest day of the year.

The shortest day of the year

The winter solstice, which takes place this Saturday, officially marks the transition into winter. As we explained in a previous article, this is the time when the northern hemisphere of the Earth is furthest from the Sun.

Larousse defines the solstice more precisely as “the time of the year when the Sun, in its apparent movement on the ecliptic, reaches its strongest boreal or southern declination, and which corresponds to a maximum or minimum day length” .

For the winter solstice, it will therefore be the shortest day of the year. And where the night will be the longest.

According to the data sent to actu.fr by the Paris Observatory, the sun will rise at 8:43 and two thousandths and will go to bed at 4:54 p.m. and seven thousandths to the capital. Its hours can of course vary depending on where you are in France.

The Sun sets earliest on December 11

Although it is the shortest day, December 21 is not the day when the Sun sets earliest.

According to the Paris Observatory, the earliest sunset was on December 11. Looking back, we can see that he went to bed at 4:52 p.m. and a thousandth that Wednesday (Paris time again).

This discrepancy has a somewhat complicated explanation that we will simplify here. For everyone to coordinate, we need regular, uniform time. There's no question of winding your watch every day, it's noon at the same time every day. This is called the average sun.

But nature is not so perfectly calibrated. The Sun rotates on its axis, but its orbit is not completely circular. So depending on the day, the Sun can slow down or speed up. This is called the true sun: he is the one we see on sundials.

But there is therefore a gap between these two calibrations of time. This is why the earliest sunrise does not fall on the same day as the winter solstice.

As for the latest sunrise, at 8:45 and seven thousandths, it does not occur before December 31 for the same reason.

Follow all the news from your favorite cities and media by subscribing to Mon Actu.