kilogram

Veritasium explains why the kilogram is being redefined in terms of Planck's constant rather than a physical metal artifact. It visits NIST to show the Kibble balance and why measuring mass precisely is hard.

Veritasium explains the effort to redefine the kilogram, which was still defined by a physical artifact, and how a near-perfect silicon sphere from the Avogadro project helps. It also covers the history of the unit's odd naming.

Veritasium explains that the US signed the Metre Convention in 1875 and that all US customary units are officially defined in terms of metric standards. It also touches on the standard kilogram.