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Video from The 2021 Robert Hofstadter Memorial Lectures: What happened to the kilogram?

Event Recap

For 130 years, a cylinder made of a platinum-iridium alloy stored near Paris was the official definition of a kilogram, the basic unit of mass. This all changed on May 20, 2019: a kilogram is now defined by a fundamental constant of nature known as the Planck constant h, which relates the energy of a photon to its frequency: h= 6.62607015 10-34 kilograms times square meters per second.

Sounds complicated? In this talk, I will provide the reasons for changing the definition of the kilogram, give simple explanations what the new kilogram is conceptually, and explain how objects with exactly known masses can be realized using advanced technology. 

Webinar link: https://stanford.zoom.us/j/95238055074?pwd=bzVQNGYvaHpyRml3VEo4ZzBNVDNydz09

Passcode: 642168

April 12, 2021 - 4:30pm to 5:30pm
Virtual

Free

Event Sponsor: 
Applied Physics/Physics Colloquium
Contact Email: 
dmoreau@Stanford.EDU
Contact Phone: 
650-723-4347

This event belongs to the following series