What Physical 'Life Force' Turns Biology's Wheels?

A long-form account of how the bacterial flagellar motor actually works — a self-assembling, 5:2-geometry rotary engine resolved by cryo-EM in 2020 after 50 years of guesses. Protons flowing into the cell push a pentagonal turnstile 1/10 of a revolution at a time; the whole thing is driven by the proton motive force, Peter Mitchell's 1961 idea that cells run on an entropic charge gradient across a membrane.