What is an inch? Well, I looked it up, and it’s like the size of three lentils side-by-side: two horizontal and one vertical. Those three lentils, in any case.
Needless to say, that was not a particularly precise measurement.
It can express the same general size, but you can’t launch into space with precision like that.
And metric’s no better, just different.
No matter where you look, you can only ever find measurements that refer to other measurements.
I have looked extensively and am fairly certain no measurement is absolute.
You can go down to atoms, and you will find electrons in motion. So far as we can tell, those orbit protons randomly. But is it really random?