Because the question of how life began is so big, it transcends ... very rare on early Earth. When they just mixed those ingredients together in a beaker, or in geologic cracks without heat ...

Though there is no single agreed-upon date, the Archean looks promising as a time when big geological changes were happening on Earth. "It points to a really important transition," said Nadja ...

The Earth was once more released from the grip of the big chill between 5 and 3 million years ago, when the sea was much warmer around North America and the Antarctic than it is today. Warm ...