In 2018 the International System of Units will be redefined in terms of fundamental constants. Why this change is taking place is explained in this short film presented by Stephan Schlamminger of the National Institute of Standards and Technology (NIST).

This means that base units such as the metre, the second and the kilogram will be redefined in terms of fundamental quantities such as the speed of light (c), the Planck constant (h) and the charge of the electron (e). Doing so will bring together two of the grand theories of modern physics: quantum physics and Einstein’s general theory of relativity.

This video is part of our 100 Second Science series, in which researchers give concise presentations covering the spectrum of physics.