Physical Society Colloquium
Does E=m c2?... and the World's Most Precise
Mass Measurements
Simon Rainville
Physics Department
MIT
The concept of mass is of primary importance in all branches of Physics. Mass
is a fundamental property of matter and one of the three basic quantities of
the International System of Units. Yet, the precision with which it can be
measured is several orders of magnitude below what can be done for time and
length. Precise mass measurements play key roles in several fundamental tests
of Physics and have diverse and interesting applications. A few examples like
a possible atomic definition of the kilogram, a determination of the fine
structure constant, and a new test of Einstein's famous relation
E=mc2 will be discussed. By simultaneously trapping two different
ions in a Penning trap and precisely controlling their relative motions, we
have recently achieved mass comparisons with a relative accuracy of about
10-11 - close to an order of magnitude improvement on the best
mass measurements in the world.
Friday, April 4th 2003, 15:30
Ernest Rutherford Physics Building, Keys Auditorium (room 112)
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