ZURICH -SWITZERLAND
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Zurich and Switzerland are famous for clocks and watches. The first clocks were sundials or shadow clocks. Next came hourglasses. Then in 14th century Europe it was found that a suspended rock pulling on a gear could be lowered slowly by a swinging bar which halted and released the main gear. The next step increased accuracy by adding a pendulum. Ship exploration was all the rage but a shipboard pendulum clock couldn't work because the motion messed it up. By 1675 the first clock with an accurate mainspring was developed.Today the most accurate clock uses atoms. The electron in an atom spins around when the atom absorbs energy. The number of spins per second (frequency) is measured and acts like a pendulum. One second is defined as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom. Atomic clocks are so accurate because they aren't affected by humidity, air pressure or bubble gum.
