Joe Palca

Last April, a volcanic eruption in Iceland sent a cloud of ash billowing toward Europe. That ash was potentially hazardous for aircraft, and authorities decided to ground all flights — inconveniencing tens of thousands of travelers — rather than risk an accident. A new study suggests that this was the right decision.

Susan Stipp, a professor of nanotechnology at the University of Copenhagen, was one of the people whose plans were frustrated by the volcanic cloud. She had colleagues who needed to get home to Denmark, and samples were delayed en route from Scotland.

News that air traffic controllers had fallen asleep at their posts has brought a chorus of outrage. But if you think it's easy for humans to stay awake and vigilant when working in the middle of the night, think again. The truth is, there's no one-size-fits-all answer for making sure nodding off never occurs.

The problem is humans aren't nocturnal, but modern society demands some people work at night. So is there anything people can do to be certain they stay awake during the graveyard shift?

Radiation is a scary thing. It is invisible and its effects on the human body are not completely understood. But many people overestimate the risk of radiation exposure, especially when it comes to nuclear power. NPR's Joe Palca in Tokyo has been thinking a lot about the public's perception of radiation.

No one likes things to break. We don't like holes to appear in airplane cabins unexpectedly; we don't like bridges to collapse; we don't like radioactivity to leak from nuclear power plants.

A newly excavated site in central Texas contains evidence that the first human settlers in the Lone Star state arrived more than 15,000 years ago. That's more than 2,000 years earlier than scientists originally thought.

The discovery should help end a controversy about whether a culture known as Clovis was the first to settle in the Americas. The site is on Buttermilk Creek, north of Austin, and there are plenty of good reasons why our ancient ancestors would have camped here.