Earth is like one giant recycling bin.
The energy we get from the sun is constantly renewed, but water and other chemical elements (like carbon and nitrogen) on earth are used over and over again as living things take them in, use them, and then put them back into the environment. These recycling processes are called “biogeochemical cycles” and include the water cycle, the carbon cycle and the nitrogen cycle.
When I was at NASA’s Goddard Space Center, a scientist showed us this video he made about how the carbon cycle works. You can see for yourself how every time you eat a banana or drive a car, you are part of the cycle.
NASA’s Climate Kids website also has some cool explanations of how the carbon cycle works. You can actually blow through a straw into a liquid that is an acid-indicator and watch the liquid become more acidic from the carbon dioxide in your breath! I’m trying to figure out how to make this experiment safe and easy to do at home, and will post it when I figure it out.