Historical models of the Solar System

The models of the Solar System throughout history were first represented in the early form of cave markings and drawings, calendars and astronomical symbols.

The use of the Solar System model began as a resource to signify particular periods during the year as well as a navigation tool which was exploited by many leaders from the past.

This scientific method of deriving a model of the Solar System is what enabled progress towards more accurate models to have a better understanding of the Solar System that civilization is located within The Nebra Sky Disc is a bronze dish with symbols that are interpreted generally as the Sun or full moon, a lunar crescent, and stars (including a cluster of seven stars interpreted as the Pleiades).

The disc has been attributed to a site in present-day Germany near Nebra,[1] Saxony-Anhalt, and was originally dated by archaeologists to c. 1600 BCE, based on the provenance provided by the looters who found it.

[4] In biblical cosmology, the firmament is the vast solid dome created by God during his creation of the world to divide the primal sea into upper and lower portions so that the dry land could appear.

[11] The Xuanye (Ubiquitous darkness) theory attempts to simplify the structure by implying that the Sun, Moon and the stars are just a highly dense vapour that floats freely in space with no periodic motion.

[12] Since 600 BCE, Greek thinkers noticed the periodic fashion of the Solar System (then regarded as the "whole universe") but, like their contemporaries, they were puzzled about the forward and retrograde motion of the planets, the "wanderer stars", long taken as heavenly deities.

[13] Shortly after, circa 450 BCE, Anaxagoras was the first philosopher to consider the Sun as a huge object (larger than the land of Peloponnesus[15]), and consequently, to realize how far from Earth it might be.

This model is the first one that depicts a moving Earth, simultaneously self-rotating and orbiting around an external point (but not around the Sun), thus not being geocentrical, contrary to common intuition.

He claimed that circles and spheres were the preferred shape of the universe and that the Earth was at the centre and the stars forming the outermost shell, followed by planets, the Sun and the Moon.

Eudoxus of Cnidus, student of Plato in around 380 BCE, introduced a technique to describe the motion of the planets called the method of exhaustion.

[33] Around 350 BCE Aristotle, in his chief cosmological treatise De Caelo (On the Heavens), modified Eudoxus' model by supposing the spheres were material and crystalline.

[35] By 330 BCE, Heraclides of Pontus said that the rotation of the Earth on its axis, from west to east, once every 24 hours, explained the apparent daily motion of the celestial sphere.

Simplicius says that Heraclides proposed that the irregular movements of the planets can be explained if the Earth moves while the Sun stays still,[36] but these statements are disputed.

[39] Following the heliocentric ideas of Aristarcus (but not explicitly supporting them), around 250 BCE Archimedes in his work The Sand Reckoner computes the diameter of the universe centered around the Sun to be about 1014 stadia (in modern units, about 2 light years, 18.93×1012 km, 11.76×1012 mi).

Around 210 BCE, Apollonius of Perga shows the equivalence of two descriptions of the apparent retrograde planet motions (assuming the geocentric model), one using eccentrics and another deferent and epicycles.

[45] During the period 127 to 141 AD, Ptolemy deduced that the Earth is spherical based on the fact that not everyone records the solar eclipse at the same time and that observers from the North can not see the Southern stars.

He also re-arranged the heavenly spheres in a different order than Plato did (from Earth outward): Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn and fixed stars, following a long astrological tradition and the decreasing orbital periods.

[49] His model was not widely accepted, despite his authority; he was one of the earliest developers of the system of the seven liberal arts, the trivium (grammar, logic, and rhetoric) and the quadrivium (arithmetic, geometry, music, astronomy), that structured early medieval education.

[50] Nonetheless, his single encyclopedic work, De nuptiis Philologiae et Mercurii ("On the Marriage of Philology and Mercury"), also called De septem disciplinis ("On the seven disciplines") was read, taught, and commented upon throughout the early Middle Ages and shaped European education during the early medieval period and the Carolingian Renaissance.

[57] Ibn al-Haytham claimed that the epicycles Ptolemy introduced are inclined planes, not in a flat motion which settled further conflicting disputes.

[82] By then it had been established beyond doubt that planets are other worlds, and stars are other distant suns, so the whole Solar System is actually only a small part of an immensely large universe, and definitively something distinct.

[88] When in 1781 William Herschel discovered a new planet, Uranus,[89] it was found it lies at a distance beyond Saturn that approximately matches that predicted by the Titius-Bode rule.

Due their star-like apparience, William Herschel suggested Ceres and Pallas, and similar objects if found, be placed into a separate category, named asteroids, although they were still counted among the planets for some decades.

Eventually, they were dropped from the planet list (as first suggested by Alexander von Humboldt in the early 1850s) and Herschel's coinage, "asteroids", gradually came into common use.

[99] Later, between 1845 and 1846, John Adams and Urbain Le Verrier separately predicted the existence and location of a new planet from irregularities in the orbit of Uranus.

[100] This new planet was finally found by Johann Galle and eventually named Neptune, following the predicted position gave to him by Le Verrier.

This fact marked the climax of the Newtonian mechanics applied to astronomy, but the Neptune's orbit does not fit with the Titius-Bode rule, so it has been deprecated from then on.

[103] In 1919 Arthur Stanley Eddington uses a solar eclipse to successfully test Albert Einstein's General Theory of Relativity,[104] which in turn explains the observed irregularities in the orbital motion of Mercury,[105] and disproves the existence of the hypothesized inner planet Vulcan.

[107] In 1950 Jan Oort suggested the presence of a cometary reservoir in the outer limits of the Solar System, the Oort cloud,[108] and in 1951 Gerard Kuiper argued for an annular reservoir of comets between 40 and 100 astronomical units from the Sun having formed early in the Solar System's evolution, but he did not think that such a belt still existed today.