Gear reduction is pretty basic mechanical engineering. It’s used everywhere and in everything. It’s a great way to give a person an introduction as how various machines work, and how to increase torque, or speed. The above contraption, made by Oskar van Deventer, has an astonishing gear ratio of 11,373,076 to 1. That means, the you would need to turn the crank 11.3 million times in order get the red gear to make one full rotation.
How does it work, well take a look at the exploded view of the contraption:
The red & green stages are what he calls grinder gears, the inside gears have one less tooth then the outside, so they spin rather slowly. Stack a few of those together, and then control it all with a regular planetary gear, and you have your 11 million to 1 ratio.
Now comes the important question. What practical purpose could this solve?
At the moment, nothing. But the theory exists, and now it just needs to become more precise, and eventually, in space we’ll need things super crazy like this. Or, you could reverse it, and get insane RPMs out of slow moving items. Something like that would work well in space I think, where there’s no friction, and tons of slow moving things.