About a quarter of the ocean's surface is a desert. Hundreds of miles of open water with almost no food in it. So when a big ship crosses one of these empty stretches, it becomes the only interesting thing for miles, and fish start trailing along behind it.Biologists have studied this for decades. Any floating object out there, a log, a clump of seaweed, a drifting coconut, a stray piece of trash, a whole ship, ends up working like a magnet for fish. To something living in all that emptiness, an

80% of our waste water flows back to nature untreated. Safe use of wastewater can help us combat water scarcity and reduce environmental pollution | Food and Agriculture Organization of the United Nations (FAO)

To build this dam, engineers first drowned a waterfall twice the size of Niagara. You could hear it roaring from 20 miles away. Then they made one of the world's biggest rivers move out of the way, just to clear room for the construction site.It's the Itaipu Dam, on the Paraná River where Brazil meets Paraguay. Work started in 1975, and the first job was the river itself. Crews spent three years carving a 1.2-mile channel through solid bedrock, 500 feet wide and 300 feet deep.They hauled away 50