Down here on the Earth, we rarely give much thought to our atmosphere, because we can’t see, smell, taste or hear it, we take it for granted. But our air is all that stands between us and the vacuum of space. We’ve got this canopy that provides us a lot more than just an atmosphere to breathe in. It definitely shields us. The atmosphere is divided into five distinctive layers, the troposphere, stratosphere, mesosphere, thermosphere and exosphere. Each layer is less dense than the one below, stretching miles above our heads. How far out it goes is depending on which scientist you talk to. Some say it ends at three hundred miles. Some say it extends out to Mars. We live in the layer closest to the ground. Here in the troposphere, the air is thickest and the pressure greatest. Our bodies are perfectly matched to these conditions.