Nell Greenfieldboyce

A small cylinder called Le Grand K has defined the kilogram for more than a hundred years. But if a scratch ever rendered it lighter, the definition of the kilo literally shifted. Time for a change.

A new study found that birds' dinosaur relatives had eggs with traces of two pigments—a red-brown one and a blue-green one. In today's birds that might produce a color such as robin's egg blue.

A new analysis of what were initially thought to be microbial fossils in Greenland suggests they might instead just be mineral structures created when ancient tectonic forces squeezed stone.

Astronaut Nick Hague and Russian cosmonaut Alexey Ovchinin were on board when their Soyuz MS-10's booster malfunctioned. The two made it out safely.

Scientists have detected plenty of planets outside our solar system. Now, they say, they've found the first moon circling one of them.

An American woman, Frances H. Arnold, has won half of the 2018 Nobel Prize in chemistry, and George Smith of the U.S. and Sir Gregory Winter of the U.K. will share the other half.

Frances H. Arnold, an American chemist, has won half of the 2018 Nobel Prize in Chemistry, and George Smith of the U.S. and Sir Gregory Winter of the U.K will share the other half.

The drug makes the usually antisocial creatures much more interested in friendly contact with other octopuses. It's one more sign that the chemistry of social behavior has deep evolutionary roots.

Scientists have developed a forecast model for predicting mass bird migrations, based in part on weather patterns.

Scientists have developed a forecast model for predicting mass bird migrations, based in part on weather patterns.

Bonobos are much more likely than common chimpanzees to share their food, a study suggests. But researchers who study sharing say human kids are more helpful and cooperative than either species.

A study suggests large mammals must learn to migrate — and they aren't exactly quick studies. It takes decades before populations can effectively move across land to find the best food.

"We don't reject any theories," said Dmitry Rogozin, the head of Russia's space agency. That includes sabotage, though he suspects it was more likely a "technological error."

Lab chimps used in medical studies are being retired to a forested sanctuary. But scientists and workers who care for the animals say some older chimps aren't healthy enough to make the transition.

Unlike other primates, human toddlers watching a competition don't appreciate victors who shove rivals out of the way. Even little kids prefer high-status characters who aren't bullies.

A new NASA probe will get closer to our sun than ever before, to try to solve mysteries like why its atmosphere is so much hotter than its surface.

NASA has selected the astronauts who will fly on the first commercial space flights.

NASA has selected the astronauts who will blast off on new commercial space vehicles set for next year. Two of them flew on the final mission of NASA's space shuttle in 2011.

Leaders make decisions for a group in the same way they make choices for themselves, a study suggests. They don't change their decision-making behavior, even when the welfare of others is at stake.

Many spiders ply the skies by riding "balloons" of silk. And they rely on something more than just the wind to take them high up and far away.