De revolutionibus orbium coelestium have begun work on his new system by that time. Most historians believe that he wrote the "Commentariolus" after his return from Italy, possibly only after 1510. At this time, Copernicus anticipated that he could reconcile the motion of the Earth with the perceived motions of the planets easily, with fewer motions than were necessary in the "Alfonsine Tables", the version of the Ptolemaic system current at the time. In particular, the heliocentric Copernican model made use of the Urdi Lemma developed in the 13th century by Mu'ayyad al-Din al-'Urdi, the first of the Maragha astronomers to develop a non-Ptolemaic
The Sun Saboteurs Earth Quarter"; and in the UK under the original title in the omnibus "Two Novels". In the future, Earth has been devastated by war and disease and supports only a primitive agrarian society. Most Earthmen live elsewhere, as émigrés on planets that are populated by alien species. The author suggests that the human species is the only one plagued by "original sin", i.e. by an innate tendency to lie, cheat, kill; aliens have come to accept these traits without understanding them. The story takes place among a group of humans in the "Earth Quarter", a ghetto on the planet Palu