NASA astronaut Scott Kelly and Russian Federal Space Agency (Roscosmos) cosmonaut Mikhail Kornienko will spend a year aboard the International Space Station.
Here's what happens if you take a photo of the sun each day at sunset, for several days in a row. You can see the sun's northward motion along your horizon.
Earth's tilt on its axis causes the seasons. The tilt causes the Northern and Southern Hemispheres to trade places, in receiving the sun's rays most directly.