Earlier we already discussed the possibility of building an entirely mechanical CPU. But let’s consider a bit different scenario: what would change if we replaced rigid mechanical components with tubes and containers filled with simple water?
Alright, this idea probably sounds quite strange. And you would be right: of course, using fluidic components instead of their electronic counterparts is not practical at all. However, it appears that it is quite possible to implement logic functions using flow of water instead of using transistors.
The following video describes the principle of building a ‘water computer’ and the way its components operate. Such mechanism could be scaled to perform more complex arithmetical operations, not just adding two numbers together. But the resulting device would not be small by any means: