The article mentions Mach numbers, but it leaves out what is most interesting about Mach’s place in the history of science, which is as a bridge to Einstein and General Relativity. Essentially Einstein read Mach and took a bunch of mind-bendingly profound but vague philosophical ideas like Mach’s Principle[0] and put together General Relativity out of it. And this self portrait gives that side of Mach too - the philosopher obsessed with phenomenology and how local perception relates to the large scale universe out there.

[0] https://en.wikipedia.org/wiki/Mach%27s_principle