The First Touchdown on a Comet
The European Space Agency's Philae lander is the first probe to touch down on a comet.
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Scientists frustrated by a lack of research dollars are turning to crowdfunding.
Doug Emlen, author of "Animal Weapons," unpacks the evolutionary arms race that pushes horns, claws, teeth and other animal defenses to the extreme.
Gus Speth, a longtime Washington insider, says it's time to consider consumerism, economic instability, and a functional democracy as core environmental issues.