Antikythera Mechanism
en.wikipedia.org
2 threads
The YouTube channel clickspring is building this in their hobby machine shop. Really goes into detail as well as guessing how they would have built it back then. Fantastic channel in general.
The last video also really demonstrates how incredibly complex the mechanism is. It manages to fairly accurately simulate the moons orbit around earth using an ingenious set of gears for example.
Next time we see gears like this happened something like after 1,500 years. Imagine where human kind would be if progress kept pace without this giant gap!