I want to know the answer to the following question:
What measurement is deemed most important to redefine in terms of physical constants?
All the background I'm provided with is that "The most urgent unit on the list for redefinition is the kilogram, whose value has been fixed for all science (since 1889) by the mass of a small cylinder of platinum–iridium alloy kept in a vault just outside Paris.". Is that enough to answer the question?
Answer: yes