Milankovitch cycles are the collective effect of changes in the Earth's movements upon its climate, named after Serbian geophysicist Milutin Milanković. The eccentricity, axial tilt, and precession of the Earth's orbit vary in several patterns, resulting in 100,000 year ice age cycles of the Quaternary glaciation over the last few million years. The Earth's axis completes one full cycle of precession approximately every 26,000 years. At the same time the elliptical orbit rotates, more slowly, leading to a 22,000 years cycle in the equinoxes. In addition, the Earth's tilt relative to the Sun changes between 21.5 degrees to 24.5 degrees and back again on a 41,000 year cycle. The Earth's axis today is tilted 23.44 degrees relative to the normal to the plane of the ecliptic. (из Википедии)