[gpm]

I believe their point is that a mile is defined to be exactly 1609.344 meters, a gallon is defined to be exactly 3.785411784 litres, a pound (mass) is defined to be exactly 453.59237 grams and so on. These are all just weird multiples of metric units at this point.

[zdragnar]

Eh, I seriously doubt that we will be changing the distance a mile represents if, for some bizarre reason, a meter gets redefined. Likewise, pounds and gallons and so forth. These measurements "defined in metric" is really more of a "formal conversion rate" ala converting between degrees F and C.

[Someone]

> if, for some bizarre reason, a meter gets redefined

Miles, feet and yards were tied to the meter in 1893 (https://en.wikipedia.org/wiki/Mendenhall_Order).

The meter got redefined 3 times since then (https://en.wikipedia.org/wiki/History_of_the_metre#Summary_o...)