Caesium
Element 55 · chemical symbol: Cs
These Vrulum profiles mention Caesium by name. Read each profile for its specific context; a mention alone does not establish composition, performance or use of the pure element.
For periodic-table data and other properties, consult the Royal Society of Chemistry periodic table.
Related technology profiles
Optical atomic clocks
Optical atomic clocks keep time by counting the oscillations of light that atoms or ions absorb, which occur at much higher frequencies than the microwaves used by today's caesium standard. Laboratory systems now report systematic uncertainties near 10⁻¹⁸, and the BIPM is preparing a redefinition of the SI second based on optical transitions, with CGPM adoption anticipated in 2030 or later.
Quantum gravimetry
Quantum gravimetry uses laser-cooled atoms to measure tiny changes in gravity, which can hint at voids, water or rock structure underground without drilling. Field and airborne tests have been reported, but survey speed and the lack of head-to-head tests against conventional methods still limit practical use.