Solar impulse: the solar airplane

If you live in Abu Dhabi, Muscat or Ahmedabad, you might have seen a weird bird flying above you. Wider than a Boeing 747 but weighing only 1% of its weight, Solar Impulse is a 4-engine solar-powered plane on its way to fly around the globe. It has absolutely no other fuel than solar energy. Flying only thanks to solar energy would have seemed impossible