The Home Planet

We think we know quite a lot about the Earth’s atmosphere, because that is where we happen to live. We breathe the air, we feel the breeze and the gales, marvel at the clouds swirling overhead. Rain and snow pace our seasons, and twenty-first century adults are well aware of the invisible layer of ozone protecting us from solar ultraviolet light, the carbon dioxide controlling the climate through the greenhouse effect, and the cloud-free and stable stratosphere above 12,000 metres (40,000 feet) where aeroplanes find refuge from turbulence. Although humans descended from oceanic creatures that ventured onto land – and consist mainly of water – the atmosphere is our new home.