Overview: Much like a cell membrane, our atmosphere forms a protective boundary between outer space and the biosphere that allows for all life to exist on Earth’s surface. Today, we’re going to talk about its composition and layers (the troposphere, stratosphere, mesosphere, and thermosphere), follow the path of a sunbeam of light as it travels through space and (potentially) reaches Earth’s surface, and discuss how the greenhouse effect can be both a good and bad thing!