Life's Little Mysteries: Science questions, answered

What's the science behind starting a fire with flint and steel?

Lab research often gives one answer about whether smiling can make you feel happier, but does that translate to the real world?

Why don't dogs claws retract like felines' do?

The causes range from innocuous media exposure to severe mental illness.

Hair shedding is normal, but when is it considered "hair loss"?

Are snorers immune to the sounds of their own snores?

There are many mysteries surrounding Europe's hunter-gatherers, but farming played a role in their demise.

The prize for the smallest animal goes to a group of microscopic species.

Do some species have instincts, or are these behaviors learned?

Earth's mass took hundreds of years to estimate, and even now, experts don't agree on the exact number.