A Turing machine is a very simple computer that manipulates symbols on a strip of tape to perform feats of logic. There isn't really much of a purpose to them these days; they exist as a novelty based on early computational theory by the great mathematician and computer scientist Alan Turing. They're made as a type of thought experiment to show the advantages and limits of mechanical computing. To really understand what a Turing machine demonstrates, you probably have to be the type who can speak binary.
Many have been made over the years, but one caught our eye on YouTube this week (video below). We didn't notice it because it's elegant or attractive--indeed, it's rather harsh-looking--but because it's entirely mechanical. It uses magnets and springs, but no electronics or even electricity. It was made by British hobbyist Jim MacArthur as a demonstration for a Maker Faire in the U.K.
Most Turing devices use a type of tape on which symbols are punched, but this one moves along a metal grid. Ball bearings are dropped into grid squares based on the data input via a series of small levers. The positions of the balls on the grid act as symbols. When one knows what they're doing, the pattern of ball bearings on the grid can be translated into a rough program.
For a logic unit, it uses a left-or-right switch mechanism to create binary input. It has up to 5 input symbols that allow for 10 "states." If that doesn't make sense to you, that's OK, it's not really supposed to. It's a technical way of saying that while this DIY machine won't catch up to a pocket calculator anytime soon, it's still an impressive feat of engineering for not having any batteries. … Read more