 Earth's atmosphere is incredibly important for life on Earth. If it wasn't for the atmosphere, we wouldn't be here talking about how wonderful the atmosphere is. Earth's atmosphere is the very thin layer of gases and particles that envelop the Earth. It contains air we breathe, it's where all our human emissions and natural emissions end up and it also plays an important role in protecting life on Earth from the harshness of space. It's stratified into various layers, from the Earth's surface to the top of the atmosphere. There's about five layers that are important to what we know as weather. So when we think about how the Earth's atmosphere is layered, we start from the surface and work our way up to space. The first layer is the troposphere. Troposphere is where all our weather happens. It's about the first 12 kilometres of space and anyone who's been in an airplane has been flying at the top of the troposphere. The next layer, in the stratosphere, we have the ozone layer. That's a critically important gas for protecting us from the sun, the harmful UV rays that come from the sun and can lead to skin cancer. The next layer is the mesosphere. That's where, if anyone's been lucky enough to watch a meteor shower, that's where the meteors hit Earth's atmosphere and burn up and create these beautiful displays of lights in the sky. Then there's this thermosphere. The thermosphere extends to about 700 kilometres above the Earth's surface. It's where those of you who know the International Space Station orbits in the thermosphere. It's also where we see the aurora Australis in the southern hemisphere or the aurora Borealis in the northern hemisphere. Then we talk about the exosphere. That's everything above 700 kilometres. That's where we have our satellites, which play an important role in predicting our weather. I'll talk about that later on.