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The Earth is surrounded by an ocean of gases we call the atmosphere. The atmosphere is important because it contains the air that most living things breathe. It also absorbs heat energy from the sun. It even recycles water by returning it back to the Earth as rain. Without the atmosphere, life as we know could not exist on Earth. The atmosphere extends about 600 kilometres (about 373 miles) above the surface of the Earth. Scientists discovered that the atmosphere is divided into layers, just like a layered cake. Each layer differs in thickness and in temperature. These layers also differ in composition – the types of gases that make up each layer.

Each layer differs in