There’s nothing that exciting about a plane that uses no fuel and emits no CO2 — I’ve been folding those since the fourth grade. A plane that uses no fuel, emits no CO2, has the same wingspan as an Airbus A340, and can transport people on international flights, though: That’s a big deal. And that’s Solar Impulse, the solar-powered plane that this month completed a successful flight from Switzerland to Belgium.

Right now, the plane is something like a superpowered hang-glider; it can only transport the pilot, and its average speed is about 43 miles per hour. (The inaugural international flight was 391 miles, about the distance from San Francisco to Los Angeles, and took 13 hours.) So it’s not imminently going to take over commercial air travel or anything. But the goal is to — eventually — be able to fly Solar Impulse around the world. After that, who knows? Getting from the Wright brothers to the Boeing 707 only took about 50 years.

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