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Following Anaximander, his pupil Anaximenes (c. 585 – c. 528/4) held that the stars, Sun, Moon, and planets are all made of fire. But whilst the stars are fastened on a revolving crystal sphere like nails or studs, the Sun, Moon, and planets, and also the Earth, all just ride on air like leaves because of their breadth. [9]
Aristotle added a fifth element, aether (αἰθήρ aither), as the quintessence, reasoning that whereas fire, earth, air, and water were earthly and corruptible, since no changes had been perceived in the heavenly regions, the stars cannot be made out of any of the four elements but must be made of a different, unchangeable, heavenly ...
A star is a luminous spheroid of plasma held together by self-gravity. [1] The nearest star to Earth is the Sun.Many other stars are visible to the naked eye at night; their immense distances from Earth make them appear as fixed points of light.
Astrophysical plasmas are also observed in accretion disks around stars or compact objects like white dwarfs, neutron stars, or black holes in close binary star systems. [45] Plasma is associated with ejection of material in astrophysical jets , which have been observed with accreting black holes [ 46 ] or in active galaxies like M87's jet that ...
The innermost spheres are the terrestrial spheres, while the outer are made of aether and contain the celestial bodies. In Plato's Timaeus (58d) speaking about air, Plato mentions that "there is the most translucent kind which is called by the name of aether (αἰθήρ)" [9] but otherwise he adopted the classical system of four elements.
Unlimited units are defined as continuous elements, such as water, air, or fire. Limiters, such as shapes and forms, are defined as things that set limits in a continuum. Philolaus believed that universal harmony was achieved in the Central Fire, where the combination of an unlimited unit, fire, and the central limit formed the cosmos.
The fixed stars includes all the stars visible to the naked eye other than the Sun, as well as the faint band of the Milky Way. Due to their star-like appearance when viewed with the naked eye, the few visible individual nebulae and other deep-sky objects also are counted among the fixed stars. Approximately 6,000 stars are visible to the naked ...
For Plato, the celestial regions were made "mostly out of fire" [1] [2] on account of fire's mobility. [3] Later Platonists, such as Plotinus, maintained that although fire moves naturally upward in a straight line toward its natural place at the periphery of the universe, when it arrived there, it would either rest or move naturally in a ...