Since 2019, the meter has been defined as the length of the path traveled by light in vacuum during a time interval of 1/299792458 of a second, where the second is defined by a hyper-fine transition frequency of caesium.
You are correctly trying to say it’s well defined, but you are complaining about the wrong comment. You should check the meaning of “arbitrary” again.
Anyway, it’s not entirely arbitrary because it was created to represent a “round” fraction of the Earth’s circumference that is similar to the length of a person’s arms. But it deviated from that too, so it’s subjective how much that counts.
Not arbitrary.
https://en.wikipedia.org/wiki/Metre
You are correctly trying to say it’s well defined, but you are complaining about the wrong comment. You should check the meaning of “arbitrary” again.
Anyway, it’s not entirely arbitrary because it was created to represent a “round” fraction of the Earth’s circumference that is similar to the length of a person’s arms. But it deviated from that too, so it’s subjective how much that counts.
Not arbitrary, pretty close to 1/40000 the N-S circumference of the earth