In lesson 2, we will look at how the earth moves in space. In addition to rotating on its axis, our planet is also constantly moving in an elliptical orbit around the sun. This orbital motion is called revolution. One revolution refers to the earth making one complete trip around the sun. It takes our planet about 365 days to revolve once. Because Earth’s axis is tilted, the northern and southern hemispheres will either be tilted toward or away from the sun. Depending on where Earth is in its revolution, this will change throughout the year. As one hemisphere tilts directly toward the sun, that hemisphere will experience summer, while the hemisphere tilted away from the sun will experience winter.

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