Stability of the Solar System that keeps the far side of the Moon away from the Earth. Mercury is in a 3:2 spin–orbit resonance. The planets' orbits are chaotic over longer timescales, such that the whole Solar System possesses a Lyapunov time in the range of 2–230 million years. In all cases this means that the position of a planet along its orbit ultimately becomes impossible to predict with any certainty (so, for example, the timing of winter and summer become uncertain), but in some cases the orbits themselves may change dramatically. Such chaos manifests most strongly as changes in eccentricity, with some planets' orbits
Terra Mariana Terra Mariana Terra Mariana (Medieval Latin for "Land of Mary") was the official name for Medieval Livonia or Old Livonia (, , ), which was formed in the aftermath of the Livonian Crusade in the territories comprising present day Estonia and Latvia. It was established on 2 February 1207, as a principality of the Holy Roman Empire but lost this status in 1215 when proclaimed by Pope Innocent III as directly subject to the Holy See. Terra Mariana was divided into feudal principalities by Papal Legate William of Modena: After the 1236 Battle of Saule the surviving members of the