Spring has arrived, if you are a weather forecaster, as it starts on March 1st, whether or nor the sun is hot or snow is thick on the ground.  This always comes ahead of the spring (vernal) equinox, which is popularly said to be the 21st March – next week.  This is when we (non-weather people) like to think that Spring actually begins.  Inevitably, it’s more complicated than this.

The Science Geek has a useful post, explaining it all.  This is how it begins:

There is a commonly held view that March 21 is the spring equinox and that the equinoxes are the two days in the year when all places on the Earth have exactly 12 hours of daylight and 12 hours of darkness.  In fact, as I’ll explain later, this is only approximately correct.  March 21 can sometimes be the date on which the spring equinox falls but its precise date varies from year to year and also depends upon where you are located.  In fact, at the equinoxes there is actually nowhere on the Earth where there are exactly 12 hours of daylight and 12 hours of darkness.

This year, the equinox (in London) is at 0430 on March 20th, but you’ll have to read the post to find out why.

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