The era of nuclear clocks is almost here: What it means for the world

Nuclear clocks could be more accurate than atomic clocks by a factor of about 10, potentially leading to improved GPS navigation and advancements in space exploration

For much of human history, civilisations have devised ways to measure time with increasing precision. From tracking the cycles of the sun and the moon to controllable methods like pendulums, humanity's focus on timekeeping has evolved. Yet, even the best methods have not been precise enough to avoid drifting over time. For instance, a traditional quartz clock loses a millisecond every six weeks.

 

Advancements have led to the development of highly precise instruments like the atomic clock, which is estimated to lose only about one second every 100 million years. However, a potential breakthrough in timekeeping—a “nuclear clock”—could soon surpass this. A paper published in Nature by an international team of scientists details a clock based on nuclear energy levels, promising a next-generation platform for ultra-precise timekeeping. So, what exactly is a nuclear clock, and how does it differ from the already advanced atomic clock?

What is a nuclear clock?

  A nuclear clock is a type of atomic clock that measures time based on changes in an atom’s nucleus. An atom's nucleus can reach an excited state when hit by a packet of energy, such as a photon with a specific frequency. This frequency is measured to track time, typically by observing a nucleus struck by an ultra-precise laser.

 

How is it different from atomic clocks?

  While atomic clocks function on a similar principle, they measure frequency by observing an entire atom rather than just the nucleus. The nucleus, which accounts for nearly 99.99 per cent of an atom’s mass, is extremely small—if an atom were the size of a football stadium, the nucleus would be the size of a marble. Exciting such a dense structure requires more energy and finer tuning, making nuclear clocks drift less and tick more times per second than atomic clocks.

 

How does it work?

  Exciting an atom's nucleus typically requires thousands or millions of electron volts of energy. However, the rare radioactive isotope thorium-229 requires only about eight electron volts to enter an excited state. Although this energy level is relatively low, scientists had to build a specialised laser system to pinpoint the exact energy range for this transition.

 

What changes?

  Nuclear clocks are believed to be about 10 times more accurate than atomic clocks, potentially revolutionising timekeeping and GPS navigation. While their primary advantages may benefit scientific research, the increased precision could also drive advancements in space exploration and defence.