If you want to go all the way down the rabbit hole, you can follow along with John Plant on YouTube, he started with a well chosen rock, and got to an Axe, fire, kilns, huts, and recently has been smelting iron source from the iron eating(?) bacteria in a local stream.[1] He generally doesn't talk, but explains things in the subtitles if you turn them on.
Machining for me, is the particular course I took... I find the whole subject fascinating, especially making gears, and gear shaped objects, which I did for 5 years. I hadn't realized until that point that properly made involute gears have a rolling contact, they never slide against each other. That's how they last so long.
Look into Precision, especially Gage Blocks, for some fascinating things.
When I finally got my own set of Gage Block, I finally deeply realized how important they were/are to worldwide precision product design.
I would like to add "measurement" to high precision as well to these lists. Our ability to do accurate measurements allowed observation of phenomena otherwise hidden. (e.g. with a 4.5 digit DMM, you'll get a solid, stable reading. With a 9-digit DMM, you'll see a 'random walk' in the LSDs - caused by all sorts of interesting phenomna)
> If you want to go all the way down the rabbit hole, you can follow along with John Plant on YouTube
He's better known by the name of his channel, Primitive Technology. Most viewers probably don't know his name. Unlike most YouTubers, he never speaks to the camera (or speaks at all), and rarely writes about himself.
Machining for me, is the particular course I took... I find the whole subject fascinating, especially making gears, and gear shaped objects, which I did for 5 years. I hadn't realized until that point that properly made involute gears have a rolling contact, they never slide against each other. That's how they last so long.
Look into Precision, especially Gage Blocks, for some fascinating things.
[1] https://www.youtube.com/channel/UCAL3JXZSzSm8AlZyD3nQdBA