C-S Wu, E. Ambler, R.W. Hayward, D.D. Hoppes, and R.P. Hudson

Discovering Parity Isn't

In 1956, the National Institute of Standards (NIST) was the National Bureau of Standards (NBS), and just as active in experimenting with fundamental physical processes.

In the early twentieth century, physicists assumed that our world is indistinguishable from its mirror image, an idea called “parity conservation.” At NBS during that slow period between Christmas and New Year's, physicists Chien-Shiung Wu, Ernest Ambler, Raymond W. Hayward, Dale D. Hoppes, Ralph P. Hudson discovered quite convincingly that our world is distinguishable from its mirror image.

The old campus of the National Bureau of Standards is now home to the University of the District of Columbia, in Washington, D.C. On November 9, 2011, Kate Kirby, APS's Executive Officer presented a commemorative plaque recognizing the UDC as an American Physical Society Historic Site, to Allen L. Sessoms, UDC President. Dr. Sessoms is a nuclear physicist and an APS Fellow (2008).

Pictured left to right: Isadora Posey, Chair of the Department of Chemistry & Physics at UDC; Kafayat Olayinka, physics major at UDC; Alan Chodos, Associate Executive Officer of APS; Beverly Hartline, Dean of Graduate Studies at UDC; Katharine Gebbie, Director of the Physical Measurement Laboratory at NIST; Allen Sessoms, President of UDC; Kate Kirby, Executive Officer of APS; Ben Bederson, Chair of the APS Historic Sites Committee; LaVonne Manning, Associate Professor, UDC Computer Science and Information Technology; Patricia Thorstenson, UDC Professor of Chemistry.

Allen Sessoms, President of UDC, and Kate Kirby, Executive Officer of APS, holding the bronze plaque.

Plaque Inscription
In 1956, at this site, which was then on the campus of the National Bureau of
Standards, physicists C-S Wu, E. Ambler, R.W. Hayward, D.D. Hoppes
and R.P. Hudson performed an experiment which revealed that in certain nuclear
processes pairs of events that are merely mirror images of each other occur
with different probabilities. This discovery revolutionized our understanding of
nature's fundamental laws.

Historic Physics Site, Register of Historic Sites
American Physical Society

This Month in Physics History
  December 27, 1956: Fall of Parity Conservation