The construction of the first nuclear clock represented a milestone in timekeeping technology, taking science beyond the limits imposed by current atomic clocks. The latter, which already offer an extraordinary level of precision, are based on electronic transitions in caesium atoms, which oscillate at regular frequencies when exposed to microwaves. This methodology has so far allowed an error of just one second over millions of years to be achieved. However, the nuclear clock goes further, using the oscillation of the nuclei of atoms, a technique that could, in theory, provide much greater precision.
The principle behind this new clock lies in the properties of the thorium-229 nucleus, whose oscillations are incredibly stable and immune to external disturbances, such as electromagnetic interference. Nuclear transitions, being more resistant to these external factors, allow time measurement with even greater stability than that provided by the electronic transitions of conventional atomic clocks. This level of precision opens the door to the study of quantum and gravitational phenomena with a precision that was previously impossible.
The application of these new nuclear clocks is not limited to improving time measurements. They have the potential to have an impact on areas such as relativistic geodesy, allowing the Earth’s gravitational variations to be mapped with millimetre precision. Their extreme sensitivity could be used to detect minute changes in the gravitational field, which could have implications for the detection of dark matter, one of the greatest mysteries of modern physics, and for conducting advanced studies on the interaction between gravity and the laws of quantum physics.
In parallel, researchers at JILA , a joint institute of NIST and the University of Colorado, have recently been able to measure the effects of general relativity on an unprecedented scale using strontium atomic clocks.
Einstein predicted that time flows differently depending on the strength of the gravitational field, and that the closer you are to the center of gravity, the slower time passes. Scientists have demonstrated this effect with astonishing precision by measuring the difference in the passage of time between two points separated by just one millimeter. This experiment not only reinforces the theory of general relativity, but also shows that gravitational effects can be studied on a microscopic scale.
The process used by JILA scientists involves the use of an “optical lattice,” a system of laser beams that creates a sort of trap for ultra-cold strontium atoms. By reducing the intensity of the laser beams and distributing the atoms in a more uniform and less dense “grid,” they were able to reduce the errors caused by interactions between the atoms and the light. This method allowed the atoms to oscillate in sync for a record 37 seconds, allowing scientists to accurately measure the time dilation predicted by Einstein.
In addition to temporal precision, this advance has implications for several areas. More accurate clocks could improve space navigation, especially on long-distance missions, where small errors in timing can translate into large deviations in trajectory. These clocks could also be used as sensors in areas as diverse as particle physics, the detection of underground natural resources and the study of the structure of the universe. The ability to accurately measure relativistic effects on microscopic scales allows scientists to explore the connection between quantum and gravitational phenomena, one of the great challenges of modern physics.
In conclusion, both the development of the nuclear clock and the innovations in the use of strontium atomic clocks represent technological advances of great importance. These new clocks not only redefine the way we measure time, but also open up new possibilities for fundamental science, allowing us to study the universe with greater precision and depth than ever before.
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