Nine science stories to watch in 2019

The precedent was set in 1967, when the definition of a second was changed to the length of time required for a cesium-133 atom to complete 9,192,631,770 oscillations. The meter followed in 1983, becoming the distance traveled by light in one 299,792,458th of a second. Anywhere in the universe, these two units of measurement would remain the same.