You know jet streams as fast-flowing air currents in the atmosphere that can help predict temperature and help planes fly faster. According to data sent back by a trio of ESA satellites called Swarm, though, there's also a jet stream deep beneath our planet's surface, and it's made of molten iron. A team of European scientists have discovered the jet stream in the Earth's outer core that's located 1,900 miles underneath its crust. It moves at 25 miles per year, three times faster than the speed of the other layers in the outer core and a thousand times faster than...