Technology on Aerth has taken a slightly different path from Earth, obviously. Magnetism, gravity, and electricity are well understood, but mana - the vital force that infuses the environment and all creatures - is both well-understood and used as a major motive force. Devices that convert mana to force and vice versa exist on Aerth just as devices that convert electricity to force and vice versa exist on our Earth. Flying machines exist, but the fact that magic can make things lighter than air has made aerodynamics slightly less important than power, and the jet engine still hasn't been developed (as if people are in a particular hurry, there's always teleporting.)