Goddard Space Flight Center, Greenbelt, Maryland 20771 

ENGINEERING COLLOQUIUM 

Monday, March 22, 1999 / 3:30 PM, Building 3 Auditorium 

Jo Ellen Barnett

ABSTRACT --  In the twentieth century, atomic clocks have brought time measurement to new pinnacles of accuracy, and its uses now extend far beyond that of simply recording the time of day.  This talk will journey into the past to examine the conceptual and technological heritage of modern modes of time measurement.  It will trace the history of timekeeping from the sundials and water clocks of the ancient world to the medieval invention of the mechanical clock, and will then show the evolutionary line extending from the pendulum clock -- the first to use a natural periodicity as regulator -- to today’s quartz crystal and atomic clocks.  The story will also include a discussion of the gradual transformation from strictly local time to a single world-wide system.  The discovery of the longitude at sea and, on land, the solution to the problem created by the railroads eventually brought the whole revolving earth into one time system. 

SPEAKER:  Jo Ellen Barnett is the Administrator of the Department of Microbiology at Mount Sinai School of Medicine in New York. She also works in an editorial capacity with a group using molecular biological techniques to construct chimeric influenza viruses for use as vaccine vectors. She is the author of "Time’s Pendulum: The Quest to Capture Time ? From Sundials to Atomic Clocks".