2021 Robert Hofstadter Memorial Lecture: What happened to the kilogram?

Topic: 
What happened to the kilogram?
Monday, April 12, 2021 - 4:30pm
Venue: 
Zoom ID: 95238055074; Passcode: 642168
Speaker: 
Wolfgang Ketterle (MIT)
Abstract / Description: 

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.


We are excited to announce that our distinguished speaker is Prof. Wolfgang Ketterle, the John D. MacArthur Professor of Physics at the Massachusetts Institute of Technology. Prof. Ketterle works on experimental research in atomic physics and laser spectroscopy and focuses currently on Bose-Einstein condensation in dilute atomic gases. He was among the first scientists to observe this phenomenon in 1995, and realized the first atom laser in 1997. His earlier research was in molecular spectroscopy and combustion diagnostics.

Prof. Ketterle's awards include the Rabi Prize of the American Physical Society (1997), the Gustav-Hertz Prize of the German Physical Society (1997), the Discover Magazine Award for Technological Innovation (1998), the Fritz London Prize in Low Temperature Physics (1999), the Dannie-Heineman Prize of the Academy of Sciences, Göttingen, Germany (1999), the Benjamin Franklin Medal in Physics (2000), and the Nobel Prize in Physics (2001, together with E.A. Cornell and C.E. Wieman).

Prof. Ketterle will also give the Applied Physics/Physics colloquium at 4:30 PM on Tuesday, April 13, 2021. Detailed information about both lectures and our speaker can be found on Physics site (link below). As in previous years, both lectures are free and open to the public via Zoom webinar.