5 ms·
It is defined in terms of the Planck constant. Now if that constant is not actually constant over time or space, the definition would be in trouble. For exampl
by gmueckl 7y ago
It is defined in terms of the Planck constant. Now if that constant is not actually constant over time or space, the definition would be in trouble.
For example, it is unclear whether the Hubble constant is, in fact, constant over time. Different measurements give different values for different time periods in the past and these have yet to be reconciled.