In cesium, there are a pair of energy states, so to make it easier, let’s refer to these as state A and state B, respectively.įirst, atoms are heated and bundled into a beam. The first thing to understand is atoms can be in different energy states, called hyperfine levels or hyperfine structure in scientific terms. But what you may not know is while they are identical in principle and function - like traditional clocks - there are many types. This is why atomic clocks are one of the most accurate devices we have to tell time. Yet, atomic clocks are more precise because natural atomic oscillations happen at a higher frequency and as a result they are more stable. ![]() Well, the natural way that atoms oscillate works similar to a pendulum in an atomic clock. You know what a pendulum in a grandfather clock is, right? It is a harmonic oscillator that uses gravity to swing back and forth, and this motion helps the clock keep time. Precise measurements – like those from atomic clocks – also help operate satellite navigation systems like GPS, Galileo, and GLONASS. And since UTC is the standard we use to keep all the clocks in the world synced, atomic clocks are pretty important. Please note, this only applies to a cesium atom currently at rest at 0 Kelvin.Īn estimated 400 clocks worldwide contribute to International Atomic Time (TAI), a time standard we use to maintain Coordinated Universal Time (UTC). “The second is 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 caesium-133 atom.” We can also refer to the true definition, which is much more complex. ![]() An atomic clock is a device that measures time using the microwave signal emitted by atoms – or the electrons in atoms – when they change energy levels.ĭid you know atomic clocks only have an error of 1 second in a span of about one-hundred million years? This makes them one of the most accurate devices in human history, at least when it comes to keeping time.Ītomic clocks measure the actual length of a second, which is the base unit we use to calculate time.Īccording to the International System of Units (SI), the time unit "second" is calculated by the time an atom in a defined state - comprised of the element caesium-133 - takes to oscillate 9,192,631,770 times.
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