Science & Tech · Science & Environment · 6 hrs ago
Thorium-based nuclear clock runs unaided for a full day
Physicists in Vienna have built a clock that uses thorium nuclei embedded in a room-temperature crystal.
The nuclei help keep a laser at a precise frequency, which the clock uses to measure time.
Most highly precise clocks rely on electrons, which can be disturbed by heat, collisions and magnetic fields.
A nucleus is more sheltered inside an atom, so a nuclear clock could eventually be more stable.
The team’s prototype ran for a full day without anyone adjusting it.
It is not yet as precise as the best optical atomic clocks, but the result shows the clock can operate on its own.
The researchers worked with a group at Germany’s national metrology institute, and the technology could someday rival atomic clocks.
Physicists in Vienna built a thorium-based nuclear clock that ran for a full day without human intervention.
Thorium nuclei embedded in a room-temperature crystal help stabilize the frequency of the clock’s laser.
The prototype uses thorium-229, whose nucleus can be switched between two energy states by ultraviolet light.
The research team is led by Thorsten Schumm at TU Wien and worked with Ekkehard Peik’s group at Germany’s PTB.
Schumm said the prototype does not yet match the world’s best optical atomic clocks.
- Who
- Physicists led by Thorsten Schumm at TU Wien, working with Ekkehard Peik’s group at PTB.
- What
- They built a thorium-based nuclear clock that ran unaided for a full day.
- When
- The article was published on October 12, 2026; the date of the clock’s run is not stated.
- Where
- Vienna, Austria; the work also involved Germany’s Physikalisch-Technische Bundesanstalt.
- Why
- The team aims to use thorium nuclei to stabilize a laser and develop a clock that could someday rival atomic clocks.
This story does not have two clearly opposing sides.
Peik and a colleague proposed building a clock based on thorium-229.
The Vienna and PTB teams first managed to excite thorium-229 nuclei with a laser.
Earth.com reported that the prototype had run for a full day without intervention.
- Run time
- A full day without human intervention
- Crystal
- Calcium fluoride, 3.1 millimeters across
- Operating temperature
- About 22°C (71°F)
- Laser wavelength
- 148 nanometers
- Thorium nuclei in the beam
- Roughly 10 million billion
- Light absorbed
- About 0.75%
What people are saying
This is not yet at the level of the world’s best optical atomic clocks, but for a first prototype it is a fantastic result
In fact, we can ‘fuse’ the thorium-229 nuclei into a room-temperature crystal, and still reach very reasonable clock performance.
What you really want is a self-stabilizing nuclear clock
The basic idea is simple: you have a laser and you have thorium. The laser changes the energy state of the thorium nuclei, and the thorium nuclei are used to stabilize the frequency of the laser.
Sources
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