alt Hacker NewsFunnily enough the metre is defined by the globe as well: the arc from the equator to North pole is defined as 10,000 km. I think this might be where the alternative angle metrics came from, which went with the metre:
full circle is 400 grad, so a right angle (10,000 km) is 100 grad.
Then minutes and seconds are factors of 100, so a centesimal minute is 1 km and 1 centesimal second is 10 m.
Originally it was defined like that, but it was fairly quickly redefined as the distance between marks on a prototype platinum bar. It's had a couple of other definitions since then, but it's currently defined "by taking the fixed numerical value of the speed of light in vacuum c to be 299 792 458 when expressed in the unit ms⁻¹, where the second is defined in terms of the caesium frequency ΔνCs".
https://www.bipm.org/en/si-base-units/metre