# "Scientists update four key fundamental constants

## New values of Planck constant, others bring world closer to revised measurement system..."

Updates to fundamental constants are carefully done, especially like the upcoming defining or redefining mass (more later on that in another post).  Many are interconnected, locked in fundamental relationships, so a change in one can not only imply, but require a change in another.  Recently, four $(4)$ were updated.

It will be interesting to see which fundamental constants need to be updated when the proton radius problem is finally "officially" solved:

$r_p=0.8412fm$ new value -4% present CODATA value
$r_p=0.8751fm$ present CODATA value

$\mu_p=2.6666\mu_N$ new value for proton magnetic moment, -4.5% present CODATA value
$\mu_p=2.7928\mu_N$ present CODATA value

Since magnetic moment, radius, charge, and mass are all interrelated, the proton's magnetic moment is locked to its radius.  The muonic measurements of the proton radius have been repeatedly verified since 2010, so this change in the proton's radius will ripple through physics WAY more than just an update to the proton's magnetic moment.

(See previous post for derivation of $\mu_p={8\over3}\mu_N$)

The Surfer, OM-IV