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 Mask of the Sun The Mask of the Sun The Mask of the Sun is an graphical interactive fiction game developed by Ultrasoft and published in North America by Brøderbund and in Europe by Ariolasoft. It was released in 1982 for the Apple II, Atari 8-bit family, and Commodore 64. The hero is Mac Steele, an archaeologist who needs to find the Mask of the Sun in order to obtain an antidote to a poison that afflicts him from an artifact that he found. The game mostly takes place in Mexico in the Aztec ruins. Gameplay is text-based; however there are some graphics, including