Milankovitch cycles
The three astronomical cycles — eccentricity, obliquity, precession — that drive Earth's ice ages on 10,000- to 100,000-year timescales.
Definition
Earth's orbit and spin axis evolve slowly under the gravitational perturbations of the other planets. Three cycles dominate: orbital eccentricity varies with periods near 100,000 and 400,000 years; axial obliquity oscillates between about 22.1° and 24.5° on a 41,000-year period; and axial precession — the 26,000-year cone of the rotation axis — shifts which hemisphere receives most sunlight at perihelion.
Together, these three modulate the total solar energy arriving at high northern latitudes during summer, the quantity Milutin Milanković identified as the key driver of glacial advance and retreat. Deep-sea sediment cores and Antarctic ice cores reveal glacial-interglacial cycles whose spectral peaks match the Milankovitch frequencies almost exactly, confirming his theory more than thirty years after his death.
History
Proposed quantitatively by Milutin Milanković while interned as a WWI POW in Budapest (1914–1918); vindicated by Hays, Imbrie & Shackleton's 1976 analysis of deep-sea sediment cores.