Earth & climate
The atmosphere
The Earth's thin blanket of air: what it is made of, how it is layered and why it protects us.
What you need first
You are surrounded by an ocean right now, even if you cannot see it: an ocean of air. This blanket of air is called the atmosphere, and it is the reason you can breathe, why there is weather, and why the Earth is not an icy, dead rock.
What air is made of
Air is a mixture of gases, and the shares surprise many people: about 78 percent is nitrogen, and only around 21 percent is the oxygen we need to breathe. The last percent is almost entirely the argon, plus a tiny share of , CO₂ for short. Water vapour is not counted in, because its share swings a lot with the weather. As small as the CO₂ share is, it plays a big role for the Earth's climate.
For breathing and burning.
Layers of the air blanket
The atmosphere is built up in layers like an onion. The lowest one is called the troposphere and reaches up about 10 kilometres where we live. Our weather happens only there: clouds, rain, thunderstorms, everything takes place in this narrow band. Inside it the air gets steadily colder with height, on average by about 6 degrees per 1000 metres. Above it lies the stratosphere with the ozone layer. Weather balloons climb up that far. Satellites circle much higher still, many of them a few hundred kilometres up. The higher you go, the thinner the air becomes. That is why climbers already struggle to breathe on high mountains, and at some point the atmosphere fades smoothly into space.
A shield for the Earth
The atmosphere is far more than air to breathe. Its , above all water vapour and carbon dioxide, work like a blanket that holds in part of the sun's warmth: without them the Earth's average temperature would be around minus 18 degrees Celsius instead of today's roughly 15 degrees. The blanket of air also blocks dangerous radiation from space, for example most of the UV radiation, and makes most small chunks of rock from space burn up before they reach the ground. You see them as shooting stars.
Exercises
0 of 6 solvedTime to try it yourself. You can't break anything, every attempt counts.
Which gas makes up the largest part of air?
About what percentage of air is oxygen?
About what percentage of air is nitrogen?
Order the parts of air by their share, from largest to smallest.
- 1Nitrogen, about 78 percent
- 2Noble gases and the tiny remainder, about 1 percent
- 3Oxygen, about 21 percent
Where does our weather happen?
Match each protective effect of the atmosphere to the right result.
Where this leads