“In September 2024, U.S. scientists made key advances towards building a nuclear clock — a step beyond an atomic clock,” according to ScienceAlert:
In contrast to the atomic clock, the transition measured by this new device happens in the nucleus, or core, of the atom (hence the name), which gives it an even higher frequency. Thorium-229, the atom used for this study, offers a nuclear transition that can be excited by ultraviolet light. The team working on the nuclear clock overcame the technological challenge of building a frequency comb that works at the relatively high frequency range of ultraviolet light. This was a big step forward because nuclear transitions usually only become visible at much higher frequencies — like those of gamma radiation. But we are not able to accurately measure transitions in the gamma range yet.
The thorium atom transition has a frequency roughly one million times higher than the caesium atom’s. This means that, although it has been measured with a lower accuracy than the current state-of-the-art strontium clock, it promises a new generation of clocks with much more precise definitions of the second. Measuring time to the nineteenth decimal place, as nuclear clocks could do, would allow scientists to study very fast processes… [G]eneral relativity is used to study high speed processes that could lead to overlaps with quantum mechanics. A nuclear clock will give us the technology necessary for proving these theories. [The clocks âoewill enable the study of the union of general relativity and quantum mechanics once they become sensitive to the finite wavefunction of quantum objects oscillating in curved space-time,â according to the abstract of the researchersâ(TM) paper.]
On a technological level, precise positioning systems such as GPS are based on complex calculations that require fine measurements of the time required by a signal to jump from one device to a satellite and onto another device. A better definition of the second will translate to much more accurate GPS. Time might be up for the caesium second, but a whole new world awaits beyond it.
As the researchers explain their paper’s abstract,
