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 ...

It's tough to know what happened on Earth thousands of years before anyone started writing anything down. But thanks to the amazing work of anthropologists and paleontologists like those working ...

We learned last year that many of the effects of climate change are irreversible. Sea levels have been rising at a greater rate year after year, and the Intergovernmental Panel on Climate Change ...