In fact, the second and candela aren&#x27;t choices aren&#x27;t that fundamental, mostly reflecting how those are measured. All the others come from the speed of light, fundamental charge, Plank&#x27;s constant, and gases constant; those are pretty fundamental to physics.<p>Avogadro&#x27;s number is used to define the atomic units, what makes a lot more sense than pushing it into metric calculations.<p>The wikipedia page is great:
<a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Metric_system#Future_developments" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Metric_system#Future_developme...</a>