Try as you might, you can't walk in a straight line without a visible guide point, like the Sun or a star. You might think you're walking straight, but as NPR's Robert Krulwich reports, a map of your route would reveal you are doomed to walk in circles.
It's difficult to build a working four-rotor helicopter that spans 100 feet and only weighs 80 pounds. It's even harder when your engine is a 0.7-horsepower person. But one team of engineering students is trying to do just that.
Over three decades, Columbia, Challenger, Discovery, Atlantis and Endeavour flew more than 100 missions. NPR takes a look back at some of the momentous video that came out of NASA's space shuttle program.
Credit: Andrew Prince, Maggie Starbard, Marina Dominguez/NPR