You can also view previously answered questions in the HSW Question Archive . You also frequently hear about atomic clocks in ads for the new clocks that automatically synchronize themselves with the atomic clock in Boulder, Colorado.
Atomic clocks are also important to a variety of scientific endeavors.
So let's start with the general notion of a clock. A clock's job is to keep track of the passage of time. The accuracy of the clock is controlled by how accurately the resonator is able to resonate at the specified frequency. An atomic clock is a clock that uses the resonance frequencies of atoms as its resonator. The advantage of this approach is that atoms resonate at extremely consistent frequencies.