There are 4 main layers of the atmosphere divided according to changes in temperature: 1) the troposphere, where weather occurs and airplanes fly, 2) the stratosphere, which contains the ozone layer protecting us from UV rays, 3) the mesosphere, the coldest layer where meteors burn up, and 4) the thermosphere, the hottest layer, within which are the ionosphere where radio waves bounce and the aurora borealis occurs, and the exosphere, which has no outer limit and blends into outer space.