William D. Phillips, Distinguished University Professor, University of Maryland
The Quantum Reform of the Modern Metric System: Mass becomes quantum, and electrical measurements become honest.
*note 4 p.m. start time and setting: 1101 A. James Clark Hall.
The modern metric system, officially known as the International System of Units (SI), has recently undergone its most revolutionary change since the inception of the metric system at the time of the French revolution. The kilogram, ampere, kelvin, and mole all have new definitions, based on fixing the values of fundamental constants of nature. Famously, the reform eliminates the artifact International Prototype Kilogram as the foundation of the unit of mass. This lecture will explain why this was necessary and how it was accomplished. Less famously, the century-old practice of having two separate unit systems for electrical metrology —“legal” and “scientific”— has disappeared with the reformed SI.
The 4 p.m. lecture is preceded by light refreshments at 3:30.
https://ireap.umd.edu/events/paint-branch-distinguished-lecture-applied-physics-2024