Weekly Scientific Misconceptions: Motions of the Earth - Part 1

Seasons: What causes the changing of the seasons?

This is an incredibly common question that I get working in a Planetarium at public institution. And it is usually adults who are confused...

DISCLAIMER:

 **No person should EVER feel shamed for not knowing something**

...but that is a topic for another post... 

So what causes the changing seasons on the Earth? Well, a simple and easy answer is that the Earth is tilted. However you may already be able to see why that answer may actually lead to more confusion.

When I say that the Earth is tilted, I mean that the Earth is tilted at approximately 23.4 degrees from the plane of our solar system. For the most part, that tilt is fixed. Ever wonder why the North Star seemingly never moves? 

A common misconception is that the earth is tilted one way in the winter and flipped the other way in the summer. This is completely wrong. 

The fixed axial tilt of the Earth is what is causing the Seasons.

I can even prove it to you...

Ready? 

Go to Australia! 

What season is it there? 

Oh, the opposite? 

Okay cool! 

Because the Earth is always tilted one direction, the earth's hemispheres experience opposite seasons. 

So what is happening? 

Imagine that the Earth is a shish kabob. Yes, a shish kabob. Imagine that there is a great skewer going straight through the planet. Entering at the North Pole and exiting through the South Pole. That skewer is tilted. If you were going to extend the northern side of the skewer, it would reach all the way to Polaris (the north star) if it were long enough. Therefore this skewer is "tilted" more in one direction, towards Polaris. So as the Earth goes around the sun, sometimes the northern Hemisphere is exposed to more sunlight (summer in the northern hemisphere) while sometimes the Southern Hemisphere is exposed to more sunlight (winter in the northern hemisphere). 

OR

Hold out your hands. Hold them in front of you with your fingers pointing at the ceiling, almost as if you’re ready to clap. Now have your right hand represent the Sun, while your left will represent the Earth. Now tilt your left hand. Just slightly. While keeping your right hand stationary, move your left around the right without ever changing the angle at which your left hand is tilted. 

This is how the Earth Orbits the Sun. This is what is creating the Seasons.

This is one of the many basic motions of the Earth.