Solar plane shows off above San Francisco

Solar plane shows off above San Francisco
You've probably heard about the Solar Impulse, a lightweight solar-powered plane that's about to fly across the US from west to east. It's covered in 12,000 solar cells and is only sturdy enough to withstand very mild weather and averages just 70 km/h. So while it won't be making any round-the-world

You've probably heard about the Solar Impulse, a lightweight solar-powered plane that's about to fly across the US from west to east. It's covered in 12,000 solar cells and is only sturdy enough to withstand very mild weather and averages just 70 km/h. So while it won't be making any round-the-world flights, that isn't what it was made for – rather, its purpose is to demonstrate what is possible, and that includes a day-and-night flight without fuel, a milestone achieved in 2010.