Editing Geocentric model (section)

==Relativity==
[[Albert Einstein]] and [[Leopold Infeld]] wrote in ''The Evolution of Physics'' (1938): "Can we formulate physical laws so that they are valid for all CS &#91;[[coordinate system]]s&#93;, not only those moving uniformly, but also those moving quite arbitrarily, relative to each other? If this can be done, our difficulties will be over. We shall then be able to apply the laws of nature to any CS. The struggle, so violent in the early days of science, between the views of Ptolemy and Copernicus would then be quite meaningless. Either CS could be used with equal justification. The two sentences, 'the sun is at rest and the Earth moves', or 'the sun moves and the Earth is at rest', would simply mean two different conventions concerning two different CS.
Could we build a real relativistic physics valid in all CS; a physics in which there would be no place for absolute, but only for relative, motion? This is indeed possible!"<ref>{{cite book| last1=Einstein|first1=Albert|title=The Evolution of Physics|date=1938| publisher=Simon & Schuster| location=New York|isbn=0-671-20156-5|page=[https://archive.org/details/evolutionofphysi00eins/page/212 212]| edition=1966| url=https://archive.org/details/evolutionofphysi00eins/page/212}}</ref>

Despite giving more respectability to the geocentric view than Newtonian physics does,<ref>{{cite book|last1=Hoyle|first1=Fred|title=Nicolaus Copernicus: An Essay On His Life and Work|date=1973|publisher=Harper and Row|location=New York|isbn=0-06-011971-3|page=87}}</ref> relativity is not geocentric. Rather, relativity states that the Sun, the Earth, the Moon, Jupiter, or any other point for that matter could be chosen as a center of the Solar System with equal validity.<ref>{{cite book|last1=Hoyle|first1=Fred|title=Nicolaus Copernicus: An Essay On His Life and Work|date=1973|publisher=Heineman Educational Books Ltd.|location=London|isbn=0-435-54425-X|page=1}}</ref>

Relativity agrees with Newtonian predictions that regardless of whether the Sun or the Earth are chosen arbitrarily as the center of the coordinate system describing the Solar System, the paths of the planets form (roughly) ellipses with respect to the Sun, not the Earth. With respect to the average [[Frame of reference|reference frame]] of the [[fixed stars]], the planets do indeed move around the Sun, which due to its much larger mass, moves far less than its own diameter and the gravity of which is dominant in determining the orbits of the planets (in other words, the center of mass of the Solar System is near the center of the Sun). The Earth and Moon are much closer to being a [[binary planet]]; the center of mass around which they both rotate is still inside the Earth, but is about {{convert|4624|km|mile|abbr=on}} or 72.6% of the Earth's radius away from the centre of the Earth (thus closer to the surface than the center).{{citation needed|date=July 2017}}

What the principle of relativity points out is that correct mathematical calculations can be made regardless of the reference frame chosen, and these will all agree with each other as to the predictions of actual motions of bodies with respect to each other. It is not necessary to choose the object in the Solar System with the largest gravitational field as the center of the coordinate system in order to predict the motions of planetary bodies, though doing so may make calculations easier to perform or interpret. A [[geocentric coordinate system]] can be more convenient when dealing only with bodies mostly influenced by the gravity of the Earth (such as [[artificial satellite]]s and the [[Moon]]), or when calculating what the sky will look like when viewed from Earth (as opposed to an imaginary observer looking down on the entire Solar System, where a different coordinate system might be more convenient).{{Citation needed|date=July 2023}}