TheMEHDEES

Aura Looks Up / Glossary

Atmosphere

Aura's Glossary

A diagram of Earth's atmosphere showing its five layers above the curve of the planet: the troposphere from 0 to 12 km where we live and airplanes fly, the stratosphere from 12 to 50 km where the ozone layer protects us, the mesosphere from 50 to 80 km where meteors burn up, the thermosphere from 80 to 700 km where auroras glow, and the exosphere from 700 to 10,000 km where satellites orbit.

Atmosphere is the air wrapped around Earth like a blanket. You cannot see it, but you are standing in it right now, and every breath you take comes from it.

It is thinner than you would think. If Earth were the size of an apple, the atmosphere would be about as thick as the apple's skin.

Does the air have layers?

It does. Five of them, stacked like floors in a building. We live on the bottom floor, where the clouds and the weather are, and where airplanes fly. Above that is the layer that holds the ozone, which blocks the Sun's harshest light. Higher up is the layer where most space rocks burn away, so you get a bright streak instead of a rock. Higher still is where the auroras glow. The top layer simply thins out into space, and that is where satellites circle around us.

Where does the air stop?

It does not stop all at once. The higher you go, the thinner it gets. Keep going up, about sixty miles, and there is so little air left that people call it the start of space.

Why does the air make the sky blue?

Sunlight is every color mixed together. The tiny bits of gas in our air bounce blue light around more than the other colors, so blue arrives at your eyes from every direction. The blue is not space. The blue is our air.

What else does the atmosphere do?

Quite a lot. It gives you air to breathe. It holds in warmth so the nights are not freezing. It burns up most of the space rocks headed our way. It is a very thin blanket doing a very big job.