Nell Greenfieldboyce

When workplace safety expert Eric Esswein got a chance to see fracking in action not too long ago, what he noticed was all the dust.

It was coming off big machines used to haul around huge loads of sand. The sand is a critical part of the hydraulic fracturing method of oil and gas extraction. After workers drill down into rock, they create fractures in that rock by pumping in a mixture of water, chemicals and sand. The sand keeps the cracks propped open so that oil and gas are released.

Government-funded scientists here in the U.S. are a step closer to being able to resume some controversial experiments with lab-altered bird flu viruses.

An asteroid the size of an office building will zoom close by Earth next week, but it's not on a collision course, NASA says.

Still, some people think this near-miss should serve as a wake-up call.

"It's a warning shot across our bow that we are flying around the solar system in a shooting gallery," says Ed Lu, a former astronaut and head of the B612 Foundation, a nonprofit dedicated to protecting humanity from asteroids.

The asteroid known as 2012 DA14 was first spotted last year by astronomers in Spain. It's thought to be about 150 feet across and made of rock.

Controversial experiments on bird flu could resume within weeks because leading influenza researchers around the world have finally called a halt to an unusual moratorium that has lasted more than a year.

The voluntary pause in the research started back in January 2012. Scientists had genetically altered the bird flu virus H5N1, changing it in ways that allowed it to spread through the coughs and sneezes of ferrets — the lab stand-in for people.