the science behind the changing seasons



When leaves begin to fall, temperatures drop and days become shorter, it can only mean autumn is on its way. No matter how hot the summer has been, the next season of the year is fast approaching, with home comforts, bronzed woodland hues and a pumpkin or two. 

For many, autumn is enjoyable because of its festivals and the sense that “life starts all over again when it gets crisp in the fall”, if you’re of the same opinion as F. Scott Fitzgerald. 

According to the astronomical calendar, the seasonal transition occurs on September 22, the date of the Autumn equinox. However under the meteorological definition, which is based on the Gregorian calendar, autumn begins earlier on September 1.

Here is everything you need to know about the changing seasons, from how the equinox works to what you can look forward to over the next few months.

Why is it called the autumn ‘equinox’?

Since night and day are nearly exactly the same length – 12 hours – all over the world the event is called the equinox, which literally means ‘equal night’ in Latin (equi – equal, and nox – night).

In reality though, equinoxes do not have exactly 12 hours of daylight. Solstices and equinoxes mark key stages in the astronomical cycle of the earth. In a year there are two equinoxes (spring and autumn) and two solstices (summer and winter).

This year, the autumn equinox takes place on Tuesday, September 22.

The dates of the equinoxes and solstices aren’t fixed due to the Earth’s elliptical orbit of the sun. They are closest in January, and most distant in July (aphelion).

The equinox marks the change of seasons, as the balance of light shifts to make for longer days or nights. Whether that means snow storms or heat waves depends on the hemisphere. 

It is also possible to see the Sun rising and setting directly in the East and West, whereas it appears off-centre at other times of year.   



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