Système International
•Seven Units: second (s), meter (m), kilogram (kg), ampere (A), kelvin (K), mole (mol), and (not used in this course) candela (cd).
•Second (s): Frequency of a certain cesium transition 9,192,631,770 cycles per second.
•Meter (m): Distance traveled by light in vacuum in 1/299,792,458 second.
•Kilogram (kg): Standard body kept at the International Bureau of weights and measures in Sèvre (France).