Welcome to BrainStuff, a production of I-Heart Radio.

Hi, Brain Stuff, I'm Lauren Vocalbaum, and this is another classic episode from our archives.

The seasons are in the midst of changing, but they're not

changing quite the same way that they used to. Is it time to redefine them?

Hey there, Brainsdough, Lauren Vogelbaum here.

If you live in Earth's middle latitudes, you're accustomed to experiencing four traditional

seasons, winter, spring, summer, and autumn, also known as fall.

That means that existence in the two bands of latitude stretching around the planet from 30

to 60 degrees both north and south of the tropics offers a lot more variety, weather-wise,

than on the equator, where there's basically a hot dry season and a hot, rainy season.

It's a similar story for the upper latitudes whose residents get a cold winter with long dark nights

and a slightly less cold summer with longer

daylight. To be technical about it there are actually two different ways of defining

the season's the astronomical definition and the meteorological definition. The astronomical definition

is based upon change in the length of days.

That's caused by the relative tilt of the Earth's axis as it revolves around the sun.

So in that system, winter is the time between the winter solstice,

the shortest period of daylight of the year, which occurs around December 22nd,

and the vernal or spring equinox, when day and night are roughly equal, which occurs around March 21st.

Spring then lasts from the vernal equinox to the summer solstice, which is the longest

daylight period of the year and happens around June 22nd.

Summer runs from then until the atumal equinox on September 23rd, another day when light and darkness

...