[_n_b_]

But... the length of a coastline is famously not definitively measurable. (https://en.wikipedia.org/wiki/Coastline_paradox)

[tavavex]

I think this article refers to some areas rising enough to have the coast move back by about 250m, not to an increase in length of the entire Japanese coastline.

[vidarh]

It does not have a well defined length in itself, but as soon as you define a method of measurement that problem goes away, so assuming the same method has been used for the old and new number there is no problem.

[philipov]

You can still say that the perimeter definitively got longer. Just add a parameter epsilon greater than zero for each possible way of measuring it, so that all of them are longer by some indefinite amount.

[jncfhnb]

It’s lower boundable though