The Earth is really, really old. Over 4 1/2 billion years old, in fact. How do we begin to comprehend a number that large? It helps to put it on a more fathomable scale. Watch to see where Earth's ...
About 4.5 billion years ago, a Mars-sized object (or perhaps a series of many smaller objects) crashed into Earth, sending bits ... into the distance. A new animation depicts that process with ...
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