NOVA: Build A Rice Paddy

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Terraced rice paddies, masterpieces of ancient engineering, have existed in China, the Philippines, and elsewhere for as long as two millennia. You don't have to be an expert to know that the building of these stepped paddies -- done without the aid of machinery -- is no minor undertaking. How, then, do farmers construct them? A casual glance might lead you to believe that farmers carve them into hillsides, using the dug-up rock to build the retaining walls and the excavated earth to level the terraces. Well, looks can be deceiving.