EARTH
Would you drink water out of a toilet, even if the toilet was never used? That’s the question asked at this display at the Exploratorium in San Francisco, Calif. It’s also a question on the minds of those working on wastewater recycling plans. PHOTO/Kathleen Canter
6) Moon could have formed from Earth after all: Reviving and revising the giant impact theory
The giant impact theory — the idea that a catastrophic collision about 4.5 billion years ago between Earth and a protoplanet about half Earth’s size created a disk of molten rock, gas and debris that consolidated to form the moon — was first set forth in the mid-1970s. Now, scientists are revisiting the age-old question of how Earth’s moon formed. New models indicate that it could have been born from the Earth following a giant collision after all.
Earth for more