faint young Sun paradox early Earth liquid water

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Early Earth stayed warm under a dimmer Sun

Earth’s early surface stayed warm enough for liquid water even though the young Sun emitted about 30% less solar radiation than it does today. Scientists call this unresolved climate puzzle the faint young Sun paradox.

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Greek cities had to work together to defeat Persia

Greek victory over the much larger Persian Empire depended on alliances between city-states. They shared resources and split military jobs among themselves in ways that no single Greek city could have managed alone.

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Red Sea species moved into the Mediterranean

>1,000 Marine Species

Since the Suez Canal opened in 1869, more than 1,000 marine species from the Red Sea have moved north and settled in the Mediterranean. Some now make up a significant part of its ecosystem.

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