Discovery of Earth's axial nutation
Descubrimiento de la nutación del eje terrestre
- Date
- 1727-1748 · confidence high
- Place
- Wanstead, England, United Kingdom
- Credited to
- James Bradley
- Field
- Cosmos & Earth
What was discovered
After twenty years of systematic measurements of star positions, English astronomer James Bradley discovered that Earth's rotation axis not only precesses but also wobbles with a small periodic 18.6-year oscillation caused by the Moon's gravitational pull, a phenomenon he called nutation.
Bradley had earlier discovered, in 1729, the aberration of starlight; both findings arose from his original attempt to measure stellar parallax.
What it led to
- greater precision in star catalogues and ephemerides
- a fuller understanding of the dynamics of Earth's axis
- the basis for modern models of Earth's rotation used in geodesy and satellite navigation