Strontium Atomic Clock: The World's Most Precise Timepiece

In the days of mechanical clocks, it wouldn't be unusual for them to be a few minutes slow or fast. Most of us have rushed into work at some time or other, thinking we're on time, only to find we're five minutes late, due to a clock at home being slow.

While mechanical clocks work with an oscillating mechanism to mark the passing of time, the most precise timepiece in the world is an atomic clock, powered by atoms that are arranged in a grid-like pattern and then stacked on top of each other.

© Science History Images / Alamy Stock Photo

The usual atoms used in clocks are a type known as "isotope caesium-133". The passing of time is measured by microwaves, which are generated by electrons jumping around the atoms, between lower and higher orbits. They absorb and release energy through a laser.

Now, as technology and science advance further, the world's most precise timepiece, the Strontium Atomic Clock, won't lose or gain even one second in 90 billion years. This is a level of precision that has never before been achieved.

For every 10 quintillion ticks only 3.5 would be out of sync. Bearing in mind that one quintillion has 30 zeros after the "1", this is a staggering level of accuracy! Prior to this, the atomic clock would accurately keep time to within one second over 300 million years.

Who created the Strontium clock?

Researchers at the Joint Institute for Laboratory Astrophysics used strontium atoms and multiple laser beams to create the clock. It is so accurate that it may be able to measure the interaction of gravity at a smaller scale than ever before.

The scientific aim is to shed light on gravity's relationship with other natural forces - something that has fascinated physicists for decades.

Research on atomic clocks began in 1945, after the American physicist and Nobel Prize winner, Isidor Isaac Rabi, discovered that the magnetic resonance of atoms could be used as the basis for a clock. The first atomic clock was built in 1949 by the US National Bureau of Standards.

Over the next seven decades, research continued, with major developments in the 1990s improving the accuracy of atomic clocks. These included laser-cooling and trapping atoms and the development of cavities for narrow laser line widths, enabling vastly improved accuracy.

The Strontium Atomic Clock is the latest development in a long line of scientific research, which led to the announcement in April 2015, by American space agency NASA, that it was deploying a Deep Space Atomic Clock because of its improved stability in comparison with existing navigational clocks.

To make the Strontium clock, scientists cooled the atoms to -273˚C and secured each one in its own space to control their interactions with each other.

What are the benefits?

On a more practical level for the general public, the atomic clock has enabled many applications that have revolutionised our day-to-day life. For example, accurate satellite navigation depends on atomic clocks being properly synchronised.

Even a difference of one microsecond could lead to the sat-nav being inaccurate by as much as 300 metres. The clocks used by sat-nav systems must be accurate to within one-hundredth of a microsecond - equating to less than a second in more than 140,000 years.

Telecommunications also rely on the accuracy of atomic clocks. When we make a call or send data via a network, it travels through different operators. The information is sent in packets and is combined back together when it arrives at its destination.

If the networks don't function at the same speed, the data highways can get congested, or some information may be lost. The International Telecommunication Union sets a standard for operators to ensure the telecom networks are running at the same speed. This level of accuracy can be met only by an atomic clock that is accurate to within one second over 3,000 years.

Scientists believe more precise atomic clocks will enable us to test theories, such as Einstein’s theory of relativity – which states clocks will run differently if they experience different gravitational forces.

The Strontium Atomic Clock is still in its early stages, so the developers say it hasn't been in existence long enough yet to confirm its accuracy over a period of time. Research will continue, although physicists are hopeful the clock's results so far are sound.

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