Trains

Sheldon is right, trains are awesome. Seriously, look at that!

By the way, do you guys know how trains stay on the tracks? The obvious answer is the little flanges on the side, but the real answer is less intuitive, as can be shown by the oxidation present on pretty much all of the aforementioned flanges, and because, were the flanges truly responsible, no train would ever be able to turn. Unlike a car's wheels, a train's are connected with a single, solid axle. So, were the train to encounter a bend, it would just run off the track.

The answer is that train wheels are, in fact, conical! The wheel contacts the rail at only a small area. When it needs to turn, the wheel slides to the left or right, decreasing the circumference per revolution on one wheel, while increasing it on the other. Isn't that interesting?