Orrery on display in Kassel at the Astronomisch-Physikalisches Kabinett and in Dresden at the Mathematisch-Physikalischer Salon. In "De revolutionibus orbium coelestium", published in Nuremberg in 1543, Nicolaus Copernicus challenged the Western teaching of a geocentric universe in which the Sun revolved daily around the Earth. He observed that some Greek philosophers had proposed a heliocentric universe. This simplified the apparent epicyclic motions of the planets, making it feasible to represent the planets' paths as simple circles. This could be modelled by the use of gears. Tycho Brahe's improved instruments made precise observations of the skies (1576–1601), and from these Johannes Kepler
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