Helicopters Helicopters are highly maneuverable aircraft that fly not by forcing air over a pair of fixed wings, like an airpbut by spinning a rotor blade […]
Heat engines In our age of fuel cells and electric cars, steam locomotives (and even gasoline-powered cars) might seem like horribly old technology. But take a […]
Fuel cells Acentury or so ago, the number of cars on Earth numbered in the thousands. Today, there are something like a billion cars—roughly one for […]
