For example, carbon dioxide and methane trap heat, helping to warm the Earth, while ozone helps block harmful ultraviolet (UV) rays from the Sun. Water vapor, which can range from 0 to 4% of the atmosphere, is also very important because it forms clouds, causes rain, and plays a big role in the greenhouse effect. The atmosphere has five main layers, which are separated by how the temperature changes as you go higher up. The lowest layer is the troposphere. It goes from the ground up to about 8 to 15 kilometers, depending on where you are and what season it is. This is where all weather happens, and it contains about 75% of the atmosphere’s total mass. As you go higher in the troposphere, the air gets colder. The top of this layer is called the tropopause, where the temperature stops dropping. Above that is the stratosphere, where the ozone layer is found. This layer warms up as you go higher because ozone absorbs UV radiation from the Sun. Next is the mesosphere, which is the coldest layer. In this layer, the temperature drops again with altitude, and it is where meteors usually burn up when they enter Earth’s atmosphere.