Don't miss the document linked in the video description. It gives some details on how the machine works.
The alphabet on the tape has 3 symbols: "b", "0", "1" - they are encoded as different positions of pegs in the physical tape. Three non-functional tape blocks mounted on the machine demonstrate the encoding of the alphabet.
There are 3 machine states "a", "b", "c". They are encoded as the major position of the plate on the left of the machine that moves up and down. The plate also has a minor position that depends on the current tape input.
The minimal universal Turing machine the author talks about is .
But this remark in the accompanying document did make me laugh:
> Another search on the internet yielded a small list of machines built by others. Several had electronic controllers controlling the mechanics. I can hear Mr. Turing say, “A computer running a computer. Whaaaat?”
I'm not sure Dr Turing would have expressed surprise in that manner, and even less sure that he would have been surprised that one computing machine could simulate the behaviour of another.
There's nothing about this that someone in Babbage's time could not have build. Removing the negatives from that statement ... this could easily have been built in Babbage's time.
However, it would not have been. A literal Turing machine needs a huge tape and a very, very long time to be able to do useful calculations. Babbage's Difference Engine could be seen to be immediately useful performing a task that was essential at the time. Babbage's proposed Analytical Engine was less obviously immediately useful, but it could do things that were obviously on the way to be useful, so might have got some speculative funding.
But a naked, vanilla Turing Machine is so obviously not (directly) useful, and no one of the time would having funding building one that was big enough to do anything of practical interest.
Is anyone else interested in this kind of thing? Looking for community.
All the "self-replicators" I've come across are either digital (e.g. Conway's Game of Life) or like the ones in this video, that is they require specialized parts as their "food." You could say they are all "carnivores" in the sense that they consume other machines. My interest is in "herbivore" self-replicators, those that reproduce by consuming raw materials and energy from their environment.
I can't help thinking about how close a water-powered lumber mill feels to full closure (i.e. it produces all the parts it uses). Humans perform the chopping, move things from station to station, and assemble the finished parts into new buildings and machines.
Usually you require a few different material "paths" for replication. You have a hard material that can be softened with chemicals for example, so it can be shaped with machinery that is softer than the end product.