Science of the Seasons

This is a panel from from Jeff Smith's graphic novel "Bone" that illustrates this funny idea.

This is a panel from from Jeff Smith’s graphic novel “Bone” that illustrates this funny idea.

You’re walking down the street, bright orange and red leaves crunching under your feet, when suddenly the sun is blotted out by a 2-foot thick layer of snow falling from the sky. It lands with a WHUMP, and now it is winter. Winter doesn’t actually happen like that, it would be cool if it did, but it also might a hurt a bit. So why doesn’t it? The shift in the seasons is gradual and it happens this way because of the Earth’s spin on its axis.

As the Earth goes around the sun, it spins in place but at an angle, its axis. This angle is what gives our planet the seasons — one of the two halves of the Earth, the northern and southern hemisphere, gets hit more directly by the sun at different times throughout the year, depending on the Earth’s position around the the sun. Summer occurs when a hemisphere is almost directly facing the sun and winter occurs in the other hemisphere that’s angled away from the sun. So, if it’s winter in Europe, than it will be summer in southern Africa because they are in opposite hemispheres.

Fall and spring are the transition times between these two seasons. You may have noticed, though, that the intensity of the seasons varies greatly in different places. Areas near the equator are less affected by the tilt of the Earth, causing them to see almost no temperature change throughout the year. The only climatal thing that changes are the two wet seasons and two dry seasons that occur on lands on the equator.

Diagram showing the axis (purple) and how it's tilted to give the seasons Coutesy of Wikipedia

Diagram showing the axis (purple) and how it’s tilted to give the seasons
Coutesy of Wikipedia

The equator is an imaginary line that cuts through the halfway point of the northern and southern hemisphere — the only land it crosses is mid-Africa, the northern part of South America and Indonesia. It is also the point where the radius of Earth is a bit larger than the rest of the planet itself. As the Earth spins at 1,000 mph, the spinning force causes the Earth’s middle to bulge and creates an imperfect sphere. These areas are not as affected by the tilt of the Earth due to the fact that they are bulging. The closer you get to the equator, the warmer it will be (and the longer that warmth will be) throughout the year, which is why the equator is home to all the rainforests.

This is a satillite view of the seasons. Notice how the green across the center, this is the equator and the rainforests.  Courtesy of Wikipedia

This is a satillite view of the seasons. Notice how the green across the center, this is the equator and the rainforests.
Courtesy of Wikipedia

It is because of the equator that there is a distinct temperature difference between the northern and southern U.S. Winter in the north means snow and 10 degree weather (maybe even qworse), whereas winter in the south means 60-70 degree weather and snow is just a dream. If it did snow in the south, people might have a heart attack and think it’s the ice age again.

The seasons have been surrounded by folk lore and tradition all throughout history, but now we know how simply they work and just how predictable they are. No matter what, spring will come after winter, and eventually the leaves will fall off the trees. Despite knowing how this part of nature works now, it’s still just as beautiful without the mystery.