You've seen the sun set, right? And if you get up early enough, maybe you've seen it rise, too. But have you ever wondered if the sun rises every day, and sets every night, where does it go when I can't see it? Well, no where. It's actually us that goes somewhere because we are on the earth and our planet is always turning, or spinning on its axis. 

Imagine a line passing through the center of the earth that goes through both the North Pole and the South Pole. We call that invisible line the "Axis". Earth spins around on this axis like a top. This spinning movement is called the earth's rotation, and the earth's rotation is what gives us a day and night. Every day. All year. 

If you're on the side of the earth that's facing away from the sun, as the earth is spinning, it's night. If you're on the side facing the sun it's, you guessed it, day. Now, hold on tight because the earth is actually moving in more ways than one. At the same time that the earth spins on its axis, it also orbits, or revolves, around the sun. This movement is called it's "revolution". 

One full orbit all the way around the sun is one revolution and the earth takes 365 days, or one year to complete a revolution. So have you got all of this so far? The earth is rotating on its axis, creating day and night. At the same time, it's revolving all the way around the sun. Now, here's the thing. As the earth is both rotating and revolving, it's not sitting straight up and down. Its axis is actually tilted just a little. It's not all that much, but this tilt causes one part of the earth to lean towards the sun. while another part of it is leaning away. This means that different parts of our planet's surface gets different amounts of sunlight and heat. 

So why am I telling you all this? Well, as the earth travels around the sun, it creates a pattern throughout the year. This pattern happens over and over again, and I'm sure you've noticed it. At certain times of the year, you see the Northern Hemisphere lean towards the sun, and the Southern Hemisphere leans away. And at other times, the Southern Hemisphere leans towards the sun, and the Northern Hemisphere leans away. That pattern, my friend, is what makes seasons. 

When the part of the world that you're living in is leaning towards the sun, it's warm and the days are long; Summer. When you're on the part that's leaning away from the sun, it's cold and days are short; Winter. In between, it's Spring or Autumn. If the earth weren't tilted, we would have the same season all year long. So revolution, rotation, orbit. Is your head spinning? Let's do a demonstration to shed a little light on these concepts. 

Okay, you're going to need a globe and a table lamp without a shade, plus a table to put them both on. Put the lamp in the center of the table and turn it on. Put the globe on one side of the table. Now hit the lights. The globe is earth, makes sense, right? The lamp at the center of the table is the sun at the center of the solar system. Now, slowly spin the globe. As the earth rotates, the sun lights up one side of the planet better than the other. It's day where the light is shining more brightly on the globe, and night where it's not. 

Now, let's see what the earth's revolution around the sun looks like. Give the globe a few spins with one hand while slowly pushing the globe in a circle around the sun, or the lamp, with your other hand. So, do you notice how the earth keeps rotating as it revolves around the sun? If this were the real sun and earth, by the time you get back to where you started, the globe would have completed 365 rotations or days. And that's another year gone by. 

So, what does this all show us? It shows that what looks to us to be the motion of the sun in the sky, is really caused by the motion of the earth. So now you know when you look up and see the sun setting or rising, it's not going around us. It's sitting pretty much at the center of the solar system while we, and the seven other planets, go around it. That sun, always got to be the center of attention.