Timeline of astronomy Rectification of Planetary Theory", eliminated the need for an equant by introducing an extra epicycle, departing from the Ptolemaic system in a way very similar to what Copernicus later also did. Ibn al-Shatir proposed a system that was only approximately geocentric, rather than exactly so, having demonstrated trigonometrically that the Earth was not the exact center of the universe. His rectification is later used in the Copernican model. Nicolaus Copernicus publishes "De revolutionibus orbium coelestium" containing his theory that Earth travels around the Sun. However, he complicates his theory by retaining Plato's perfect circular orbits of the planets. A brilliant
Bodhisattvas of the Earth more references to the Lotus Sutra in his commentaries than any other sutras. His commentaries focused primarily on the 15th (Emerging from the Earth) and 16th (Life Span) Chapters of the Lotus Sutra. Dōgen made numerous speculations about the significance of the bodhisattvas who emerged from the underground. As conceived by Dōgen, the stories of the underground bodhisattvas and the Buddha's inconceivable life-span serve as a fundamental shift in the development of East Asian Mahayana understanding of Buddhahood, an immediate attainment based on fundamental awakening rather than an achievement based on lifetimes of arduous practice. This can be conceived as