Why We Use Atoms to Tell Time
The best atomic clocks only lose one second per 100 million years.
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Transcript
For most of human history, what is known as a “second” was based on an astronomical measurement of time.
That is, a second was a particular division of the amount of time that it took Earth to orbit the Sun.
Typical clocks, with pendula or quartz, keep reasonable track of all those seconds.
But, they can be affected by environmental variables like gravity, manufacturing errors, or temperature. They are too inaccurate for precision-based applications like GPS and cell phone networks.
Scientists needed a way to measure and standardize the second that was much more precise.
Their solution? Atoms!
Because atoms change energy states, or resonate, at a constant rate, they make perfect time-keepers.
So, scientists designed an atomic clock using atoms of cesium!
In an atomic clock, low-energy cesium atoms in a tube, called a resonator, are bombarded with radio waves until they resonate, or jump, to their higher energy state.
The number of oscillations of radio waves, or frequency, that it takes to excite the cesium atoms, is the measure of a second.
By the time 9,192,631,770 oscillations of radioactivity have forced the cesium to change energy states, one—internationally standardized—second has passed.
At the end of the resonator, a detector tracks the high-energy cesium atoms. If the radio waves are set to the correct frequency, all the cesium atoms will resonate. If they don’t, scientists know that the frequency must be adjusted.
The most precise atomic clocks in existence only lose one second per 100 million years!
Atomic clocks truly set the standard for measuring time!
That is, a second was a particular division of the amount of time that it took Earth to orbit the Sun.
Typical clocks, with pendula or quartz, keep reasonable track of all those seconds.
But, they can be affected by environmental variables like gravity, manufacturing errors, or temperature. They are too inaccurate for precision-based applications like GPS and cell phone networks.
Scientists needed a way to measure and standardize the second that was much more precise.
Their solution? Atoms!
Because atoms change energy states, or resonate, at a constant rate, they make perfect time-keepers.
So, scientists designed an atomic clock using atoms of cesium!
In an atomic clock, low-energy cesium atoms in a tube, called a resonator, are bombarded with radio waves until they resonate, or jump, to their higher energy state.
The number of oscillations of radio waves, or frequency, that it takes to excite the cesium atoms, is the measure of a second.
By the time 9,192,631,770 oscillations of radioactivity have forced the cesium to change energy states, one—internationally standardized—second has passed.
At the end of the resonator, a detector tracks the high-energy cesium atoms. If the radio waves are set to the correct frequency, all the cesium atoms will resonate. If they don’t, scientists know that the frequency must be adjusted.
The most precise atomic clocks in existence only lose one second per 100 million years!
Atomic clocks truly set the standard for measuring time!
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