The apparent annual cycle of movements of the sun The rotation of the Earth accounts for the The distance from the Earth to the sun is imperceptible The Earth's centre is not the centre of the universe. In 1514 he 'published' a small hand written book which ![]() Such quotations as: God has founded the Earth and it shall not be moved. Orbits must be circular as the circle was the 'perfect shape' so the church argued that theĮarth must be the centre of the universe as it was on Earth that Christ was born. Just as the Greeks insisted that the Earth must stay still and that all However this idea was still not well received, That had been held by the Greek, Aristarchus. Copernicus revived the model of the Solar System Ptolemy had to add another epicycle on the first epicycle to get the correct planetaryĬopernicus is the Latin form of his name. Observations until slightly more accurate measurements were made and this meant that Seemed to be moving backwards when seen from the Earth. (Figure 3).Įpicycle moved round the deferent there would be times (such as A to B) when the planet He imagined a small circle (the epicycle) rotating on a Ptolemy (85-165 AD) attempted to solve the retrograde motion by Also each planet did not change its distance from the Earth theīrightness of the planet should stay the same – it doesn't! Planets on a steadily rotating crystal sphere would always move in the sameĭirection through the sky. Sphere was called the Prime mover – the other spheres were fixed inside this outer Velocity (it rotates through equal angles in equal times) within the outer sphere. The retrograde motion of Mars is shown in Figure 2.Įach sphere was supposed to have a constant angular What was known as "retrograde motion", the backwards movement in the sky of some of the However Aristotle's theory did not explain the real difficulty. However, Aristotle was more respected and so it was his theory that was In 280 BC Aristarchus (310-230 BC) solved the problem by putting the SunĪt the centre. Figure 1 shows the spheres to which the Sun and planets were Heavens were made of up to 55 concentric, transparent spheres, each one carrying the Sun,Ī planet or some stars. To explain this, scientists put forwardĪristotle (384-322 BC), Eudoxus and others proposed that the Of the Solar System with all the planets circling round it. Three probably the one that caused most trouble was the need to have the Earth in the centre Material, and cannot change their intrinsic properties (e.g., their brightness). The objects in the heavens are made from perfect That agreed with their three basic ideas about the Solar System.Ģ. Tried to explain the movement of the planets. Motion' you will know the problems that faced the astronomers in ancient times when they If you have read the file called 'Planetary
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