Low eccentricity is needed for habitability, especially advanced life. High multiplicity planet systems are much more likely to have habitable exoplanets. The grand tack hypothesis of the Solar System also helps understand its near-circular orbits and other unique features. See also Equation of time Footnotes References Further reading External links World of Physics: Eccentricity The NOAA page on Climate Forcing Data includes (calculated) data from Berger (1978), Berger and Loutre (1991). Laskar et al. (2004) on Earth orbital variations, Includes eccentricity over the last 50 million years and for the coming 20 million years. The orbital simulations by Varadi, Ghil and Runnegar (2003) provides series for Earth orbital eccentricity and orbital inclination. Kepler's Second law's simulation Orbits