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
Admiralty in the 16th century has organized the fleet into squadrons from at early 13th century and certainly during the 16th century. In 1560 three squadrons were operating in the Channel, Irish Sea and North Sea Until the 16th century, admirals were high officials under kings, and were charged with protecting the realm from sea attack. The English navy's Narrow Seas Squadron also called as the Eastern Squadron mainly operated in the two seas which laying between England and Kingdom of France (the English Channel particularly the Straits of Dover) and England and the Spanish Netherlands later the Dutch Republic (the southern North Sea). Include: