The eccentricity cycle affects how much more sunlight the Earth receives when it is closest to the Sun ( perihelion) than when it is furthest from the Sun ( aphelion) and also enhances or decreases the effect on sunlight of the other two irregularities. Precession: In a cycle of a little over 20,000 years, the point of the Earth's axis wobbles so that the north axis points now to Polaris (the North Star) but will eventually point to Vega before returning to Polaris.īut Milankovitch wasn't just interested in tracking changes in sunlight with his model - he wanted to explain why ice ages occurred, why at various times in the history of the Earth glaciers were formed and later melted away.
