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Once we used to watch space from Earth. Now we can watch the Earth from space. It is half a century since the first satellites beamed back their information. Space offers us a position from which we can look at ourselves and our ecosphere. We can record the transformation of our habitat - the drying of river estuaries, the disappearance of islands beneath the sea, the melting of polar icecaps. We can see the Earth as a single breathing entity. Planet Earth is a collection of astonishing satellite imagery that has been gathered by the German Space Centre in collaboration with space centres from Mexico to India and with its partners at NASA. The photographs have been made by machines in space, not by intrepid astronauts. The photographs have been processed through computers and can reveal more than is normally visible to the human eye - the floor of the ocean bed, geological strata and the eye of the hurricane. At first Planet Earth appears as a catalogue of the unfamiliar. Much of the information is astoundingly beautiful but unrecognisable. Gradually, as the captions are read, the data is translated, then the shapes and colours begin to become legible. The evidence of civilisations