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A Chinese space lab the size of a city bus will soon be falling back to Earth, and no one knows exactly where bits of it might crash down.

Genetic mutations are the driving force of evolution, and now scientists have managed to study the effect of mutations in exquisite detail by watching what happens as they pop up in single cells.

Only about one percent of mutations were bad enough to kill off the cell, according to a report published Thursday in Science. Most of the time, these small changes in its DNA appeared to have no effect at all.

Everyone from NASA to the cast of The Big Bang Theory is reacting Wednesday to the death of acclaimed physicist Stephen Hawking, known for his work on understanding the nature of black holes.

In the brave new world of synthetic biology, scientists can now brew up viruses from scratch using the tools of DNA technology.

The latest such feat, published last month, involves horsepox, a cousin of the feared virus that causes smallpox in people. Critics charge that making horsepox in the lab has endangered the public by basically revealing the recipe for how any lab could manufacture smallpox to use as a bioweapon.

A rocket more powerful than any other flying today is scheduled to blast off Tuesday for the first time, if all goes well.

Even very young babies can tell the difference between someone who's helpful and someone who's mean — and lab studies show that babies consistently prefer the helpers.

But one of humans' closest relatives — the bonobo — makes a different choice, preferring to cozy up to the meanies.

That's according to experiments described Thursday in the journal Current Biology, by scientists who wanted to explore the evolutionary origins of humans' unusually cooperative behavior.

The end of the year is a time of holiday gift giving, and finding just the right gift can sometimes feel like an impossible task. But folks at an animal eyeball lab say that a gift they've just received, partly thanks to NPR, has made this the "best Christmas ever."

It's a massive whale eye, probably from a blue whale, and the story of how it ended up at the lab starts in the 1960s.

Scientists could soon resume controversial experiments on germs with the potential to cause pandemics, as government officials have decided to finally lift an unusual three-year moratorium on federal funding for the work.

The research involves three viruses — influenza, SARS, and MERS — that could kill millions if they mutated in a way that let the germs spread quickly among people.

Copyright 2018 NPR. To see more, visit http://www.npr.org/.

SCOTT SIMON, HOST:

President Trump has formally told NASA to send U.S. astronauts back to the moon.

"The directive I'm signing today will refocus America's space program on human exploration and discovery," he said.

Standing at the president's side as he signed "Space Policy Directive 1" on Monday was Apollo 17 astronaut Harrison Schmitt, one of the last two humans to ever walk on the moon, in a mission that took place 45 years ago this week.

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