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Faint Young Sun

Scientists struggle to understand how early Earth stayed warm enough for liquid water

By
12:28pm, April 18, 2013

Here’s a climate puzzle — one that goes back to Earth’s infancy some 4.5 billion to 2.5 billion years ago. The sun was much dimmer back then. Far less solar radiation reached the planet. Earth should have been a frozen wasteland. But all geologic signs point to a young planet awash in liquid water, with the first life-forms emerging. Scientists call this conundrum the “faint young sun paradox.”

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