We watched the Mythbusters tackle the “Airplane on a Conveyor Belt” issue last night. They did not really build a huge conveyor belt (they essentially used a long canvas tarp to pull the runway out from under the plane), and so the result (the airplane took off) won’t really satisfy everyone. But, it remains the right answer.
Here’s some background: the kottke post that started it all, the explanation for the scientifically minded (the comments are fun), and kottke’s liveblogging of the Mythbusters episode.
Here’s how I try to explain it. An airplane flying through the air is virtually no different than one “flying” on the ground. The one on the ground is not (yet) going as fast as the one in the air, and there’s a miniscule amount of friction acting on the bearings in the plane’s wheels, but really, they are moving under the same laws of physics. Airplane pushes on the air, and moves forward. What the ground, or the conveyor belt are doing to the wheels is largely irrelevant. No matter how fast the conveyor belt goes, all it is acting on are the wheels of the airplane, not the plane itself. It can make those wheels spin crazy fast, but the plane will still take off.
Oh, and I like the sentiment of kottke’s t‑shirt, but I’d like a picture of a plane on it, frankly. And a conveyor belt.