[conservatism_IS_compassion]

6.022 × 10²³ DOLLARS

$1 for each molecule in 2 grams of H₂ . . . .

[FredZarguna]

Actually, within the limits of significance it doesn't really matter, but ... the definition is the number of carbon atoms in a sample of exactly 12 grams pure carbon 12.

I can't now find a reference, but I vaguely recollect that hydrogen hasn't been used since 1933.

Hydrogen always seemed to make more sense to me. No nuclear binding energy to account for if the sample is pure ¹₁H. Effectively the mass of 18 grams of H₂ would be identical to the mass of a 2 moles of electrons plus a 2 moles of protons -- the electron-proton binding energy is, I believe, negligible to the degree of precision measurable.

But while conceptually simpler, I believe the constant itself was more easily fixed by x-ray crystallography. I first learned of it as 6.02 x 10²³ then as 6.023 x 10²³. It was changed [to four significant digits] in 1973, I think to 6.022 x 10²³.

Anyway, the paper a trillion dollar Zimbabwe note is printed on has to be worth more than the currency, and eventually, even the mole will be too small. Then they'll print googolbucks.