Why in news?
An international team of scientists carried out the largest optical clock comparison across three continents in mid‑2025. Their success is expected to lead to a redefinition of the “second” by the year 2030 using optical atomic clocks.
What is an optical atomic clock?
- Unlike traditional caesium clocks that use microwave frequencies, optical atomic clocks measure time using light waves in the optical spectrum. Atoms like strontium‑87 and ytterbium‑171 have extremely stable optical transitions.
- The atoms are trapped in an optical lattice or ion trap and stimulated with a laser tuned to an optical frequency. Each absorption‑emission cycle produces oscillations hundreds of trillions of times per second. Counting these oscillations defines one second with unprecedented precision.
Why optical clocks matter
- Higher frequency: Optical transitions operate around 1015 Hz, roughly 10,000 times faster than microwave transitions, allowing finer time resolution.
- Extreme stability: Some optical clocks lose just one second over billions of years, improving global time synchronisation.
- Applications: They enable more accurate Global Positioning System (GPS), deep‑space navigation, radio astronomy and tests of fundamental physics.
- Global collaboration: Scientists from Europe, Asia and North America linked their clocks using fibre‑optic cables and GPS to cross‑check accuracy, paving the way for the 2030 redefinition of the SI second.
Looking ahead
- The International Bureau of Weights and Measures (BIPM) is expected to adopt optical clocks as the new time standard by 2030.
- Countries including Germany, Japan, the UK and the US are working on optical clock laboratories. India’s National Physical Laboratory is also upgrading its metrology infrastructure.