Solar Impulse Just Completed Its Momentous Flight Around the World

Solar Impulse 2 touched down in Abu Dhabi today, becoming the first fuel-free plane to successfully circumnavigate the globe. OK, so the 22,000-mile trip took a minute: The solar-powered bird lifted off from the same city in March 2015. But despite a few setbacks, the plane and Swiss pilot Bertrand Piccard (who took shifts with fellow flyer André Borschberg) touched down without incident.Solar Impulse 2 is a seriously nifty machine. Its 236-foot wingspan makes it wider than a Boeing