The Atmosphere

The thin shell of gas wrapped around our planet does an extraordinary amount of work. It gives us the oxygen we breathe, the carbon dioxide that plants need, the weather that waters our crops, and a screen that filters out the Sun's most harmful rays. Yet clean dry air is mostly just two gases, and the part that traps heat is a tiny fraction of the whole. Understanding what the atmosphere is made of, and how it is layered, is the starting point for every topic that follows on climate, pollution and human impact.

In this lesson you will learn the names and order of the four main layers, where the ozone layer sits and what it does, and the percentage make-up of clean air. You will then meet the natural greenhouse effect, the gentle warming that keeps the planet habitable, and see clearly why it is a completely different process from the thinning of the ozone layer. These foundations make the later topics on climate change, acid rain and ozone depletion far easier to master.