Changes

[[Johannes Kepler]] used Brahe's measurements to improve the [[Heliocentrism|heliocentric]] system Copernicus had proposed, showing that planets had elliptical orbits around the sun.  When [[Isaac Newton]] applied the newly discovered [[gravitation|universal theory of gravitation]] to the data, he used a heliocentric model. By the 1800s, the spectacular successes of Newtonian theory and [[Maxwell's equations]] for electromagnetism had convinced practically everyone that the Sun is a preferred frame of reference, and that the laws of physics must be applied in that frame. The geocentric theory was considered to be profoundly mistaken at that time.

[[Johannes Kepler]] used Brahe's measurements to improve the [[Heliocentrism|heliocentric]] system Copernicus had proposed, showing that planets had elliptical orbits around the sun.  When [[Isaac Newton]] applied the newly discovered [[gravitation|universal theory of gravitation]] to the data, he used a heliocentric model. By the 1800s, the spectacular successes of Newtonian theory and [[Maxwell's equations]] for electromagnetism had convinced practically everyone that the Sun is a preferred frame of reference, and that the laws of physics must be applied in that frame. The geocentric theory was considered to be profoundly mistaken at that time.

Since the advent of [[theory of relativity|relativity theory]] in the early 1900s, the laws of physics have been written in covariant equations, meaning that they are equally valid in any frame. Heliocentric and geocentric plotting systems are both used today, depending on which allows more convenient calculations.

One can set the origin of one's perceived  coordinate system however one likes, but experiments can be performed that can distinguish the various theories.  One could set the origin of the Universe to be the 5th car of the Tilt-a-Whirl at Six Flags New Jersey, and work out the detailed equations of motion based on that hypothesis.  But experiments involving centrifugal and Coriolis force would quickly refute that.  There are more sensible choices of the center of one's coordinate system, and they each have their uses.  At some level of precision (fastening your seatbelt) a coordinate system fixed on you car is satisfactory.  At some higher level of precision (driving your car) a coordinate system fixed on the Earth is satisfactory.  At some higher level of precision (guiding a spacecraft to the Moon) a coordinate system fixed on the Earth's position, but not rotating with it, is satisfactory.  At some higher level of precision (guiding a spacecraft to another planet) a coordinate system fixed on the Sun's position is satisfactory.  In each case, experiments can be performed to reveal the correctness of the system.  More sensitive tests are needed as the precision increases, but tests can be performed showing that Geocentrism is not correct.  These tests were unknown at the time of Kepler, Copernicus, and Galileo; they formuated their theories on considerations of logic and astronomical observation.

 

These considerations have essentially nothing to do with the [[theory of relativity]].  They relate to what is known as Galilean relativity, which is just pre-Einstein common sense.  The only significant implication, and the effect is extremely tiny, is the precession of the various planets, particularly Mercury.

==Common Misconceptions==

==Common Misconceptions==