Earth & climate
Earth as a system
Rock, water, air and life mesh together like gears: why our blue planet is a finely tuned system.
What you need first
From space the Earth looks like a blue marble streaked with white clouds. Up close it turns out to be a giant clockwork: rock, water, air and life constantly act on each other. A big volcanic eruption can cool the Earth for a year or two, rain wears mountains down, plants change the air. Nothing on this planet exists on its own.
Four spheres, one system
Scientists divide the Earth into four great realms, the spheres: the rock sphere from the crust down to the core, the water sphere with its oceans, rivers, and clouds, the envelope of air around us, and the sphere of life from the deep sea to the mountain peaks. Cycles tie them together. The lifts water from the sea into the clouds and sends it back through rivers as rain. The turns rock into sand and back into new rock over millions of years. And carbon travels back and forth between air, plants, soils and oceans. If one part changes, all the others feel it.
Each step on the scale means ten times bigger.
The Earth in numbers
A few numbers help you picture our planet. Its circumference at the equator is about 40,000 km, roughly fifty times the distance from the North Sea to the Alps. About 71 out of 100 parts of the surface are covered by water, which is why the Earth glows so blue from space. And it is unimaginably old: around 4.6 billion years. The entire history of humankind is just a blink at the end of that long stretch of time.
A planet worth protecting
As far as we know, the Earth is the only place in the universe with liquid water, breathable air and life. That is thanks to a finely tuned interplay: the right distance from the Sun, a protective envelope of air, cycles that distribute water and nutrients. Precisely because everything is connected, our actions ripple everywhere: exhaust gases change the atmosphere, and that shifts climate, sea levels and habitats. Understanding the Earth is the first step towards protecting it.
Exercises
0 of 6 solvedTime to try it yourself. You can't break anything, every attempt counts.
Which sphere do oceans, rivers and glaciers belong to?
Roughly how large is the Earth's circumference at the equator?
According to the text, how many out of 100 parts of the Earth's surface are covered by water?
Match each of the Earth's spheres to the fitting example.
How many kilometres is one quarter of the Earth's 40,000 km circumference?
The Earth is unimaginably old: about … years.