Rather than going smaller, our computers could go bigger. It is possible to replicate the functions of a transistor using water. In what is called the hydraulic analogy, a water transistor has a pressure-actuated valve that either enables or disrupts the flow of another pipe. A computer built with these transistors doesn’t need electricity at all, only water pressure. If one built what Charles Reid calls a “low/no power computer” using gravity fed water and a quarter million liquid transistors, one could build a water-based ENIAC. With only 5,600 liquid transistors, one could build a water-based Apollo Guidance Computer.
Of course, water does not flow as fast as electricity, and so the speed of these computers could not be replicated with liquid. What computational speed is necessary to fly to the moon? All that is important is that the computer is fast enough to aid the maneuvering necessary during the flight.
Perhaps, given some worldwide catastrophe that impedes the construction of microprocessors, we might still see things as complicated as space travel, but just on a longer time scale. A hydraulic computer that only functions at a rate of one cycle per second might still allow you to go to the moon. You will just have to travel at a speed one thousand times slower than Apollo 11 made the trip. Such a post-electronic technology could be called “slow computing.” Wars are conducted not in the blink of a split-second decision and the flash of a rocket motor, but with the slow trickle of water through a valve. The hydrogen boosters of ICBMs are replaced by hydrogen-lofted intercontinental balloon missiles. A spacecraft hundreds of miles in diameter crawls to the moon at a rate of a few inches per second, all to prove a point about the proficiency of one belligerent’s hydraulic-military complex to the other’s.