√ The Geocentric Modes of the Universe Explained with Fair Examples
📢 Receive Comprehensive Mathematics Practice Papers Weekly for FREE 😊 Click this link to get: ▶️▶️▶️ https://iitutor.com/email-list/ ◀️◀️◀️ While the heavens were studied by many civilisations before the ancient Greeks, these early astronomies were based on religious beliefs and astrology. The ancient Greeks were the first people to try to use logic and observation to understand the Universe. The great Greek philosopher Aristotle (384-322 BC) believed the corrupt and changeable Earth was motionless at the centre of the Universe, and that the perfect, immutable heavenly bodies were embedded in a series of concentric crystalline spheres surrounding the Earth. Aristotle proposed that 56 different crystalline spheres rotated about the Earth at different rates to account for the motion of the heavenly bodies through the skies. The moon was placed on the innermost sphere, then Mercury, Venus, the sun and the other known planets. The distant unchanging stars were embedded in the outermost crystalline sphere. Aristotle believed the Universe was not significantly bigger than the Earth. He believed the stars were only twenty Earth radii or so from the Earth. Because of his remarkable insights into a wide range of disciplines, Aristotle became the great scientific authority of antiquity. His Earth-centred or geocentric model of the Universe was to be the dominant model of the Universe for almost two thousand years. Geocentric models of the Universe place the Earth at the centre of the Universe. Ancient Greek astronomers who followed Aristotle used ever more accurate measurements of the motion of the heavenly bodies to refine Aristotle's model. About two centuries after Aristotle, Hipparchus showed that the model better predicted the motion of the heavens if the Earth was placed slightly off the centre of rotation of the celestial spheres. About the same time, Apollonius proposed that the observation that the planets changed their speed through the heavens and sometimes actually stopped and went backwards could be explained using epicycles. He suggested the planets moved in small orbits (epicycles) that were centred on and moved around a larger circle (the deferent circle). The epicycle model proposed by Apollonius is illustrated in the figure below. In AD 140 Ptolemy created a mathematical model that summarised the geocentric view of the Universe proposed by earlier astronomers. Ptolemy's model included planetary epicycles and could be used to predict the motion of the planets. Ptolemy suggested no mechanism for the complex motions within his model and, though it was based on simple circular motion, the use of epicycles made the model very complex. Ptolemy's model did, however, give reasonably accurate predictions of the positions of the planets, and it was to remain the accepted model of the Universe until the sixteenth century. Ptolemy's model, however, had its limitations. The relative sizes of the planet orbits were quite arbitrary and the model was not quite geocentric due to the equant (an offset point, about from the Earth, which the planets move around). As the planets had variable speeds the model was not quite uniform circular motion. While the model succeeded in its intended purpose, it failed from our modern point of view in that it offered no explanations for the apparent motions. Ptolemy himself would have been well aware of these limitations of his model. The epicycles of the Moon would have meant that the Moon would vary in size by a factor of almost two as it approached the earth in its orbit. Plainly this does not happen. Ptolemy's purpose was to accurately describe and predict the locations of the planets not to explain their motion. Unfortunately, Ptolemy's empirical model was later on fined into Thomas Aquinas' blend of science and theology and incorporated into the doctrines of the Catholic Church. Empirical models are often used in science to make predictions when the full theory is not well understood. PB5111 http://youtu.be/JHB3iuLp0pg
📢 Receive Comprehensive Mathematics Practice Papers Weekly for FREE 😊 Click this link to get: ▶️▶️▶️ https://iitutor.com/email-list/ ◀️◀️◀️ While the heavens were studied by many civilisations before the ancient Greeks, these early astronomies were based on religious beliefs and astrology. The ancient Greeks were the first people to try to use logic and observation to understand the Universe. The great Greek philosopher Aristotle (384-322 BC) believed the corrupt and changeable Earth was motionless at the centre of the Universe, and that the perfect, immutable heavenly bodies were embedded in a series of concentric crystalline spheres surrounding the Earth. Aristotle proposed that 56 different crystalline spheres rotated about the Earth at different rates to account for the motion of the heavenly bodies through the skies. The moon was placed on the innermost sphere, then Mercury, Venus, the sun and the other known planets. The distant unchanging stars were embedded in the outermost crystalline sphere. Aristotle believed the Universe was not significantly bigger than the Earth. He believed the stars were only twenty Earth radii or so from the Earth. Because of his remarkable insights into a wide range of disciplines, Aristotle became the great scientific authority of antiquity. His Earth-centred or geocentric model of the Universe was to be the dominant model of the Universe for almost two thousand years. Geocentric models of the Universe place the Earth at the centre of the Universe. Ancient Greek astronomers who followed Aristotle used ever more accurate measurements of the motion of the heavenly bodies to refine Aristotle's model. About two centuries after Aristotle, Hipparchus showed that the model better predicted the motion of the heavens if the Earth was placed slightly off the centre of rotation of the celestial spheres. About the same time, Apollonius proposed that the observation that the planets changed their speed through the heavens and sometimes actually stopped and went backwards could be explained using epicycles. He suggested the planets moved in small orbits (epicycles) that were centred on and moved around a larger circle (the deferent circle). The epicycle model proposed by Apollonius is illustrated in the figure below. In AD 140 Ptolemy created a mathematical model that summarised the geocentric view of the Universe proposed by earlier astronomers. Ptolemy's model included planetary epicycles and could be used to predict the motion of the planets. Ptolemy suggested no mechanism for the complex motions within his model and, though it was based on simple circular motion, the use of epicycles made the model very complex. Ptolemy's model did, however, give reasonably accurate predictions of the positions of the planets, and it was to remain the accepted model of the Universe until the sixteenth century. Ptolemy's model, however, had its limitations. The relative sizes of the planet orbits were quite arbitrary and the model was not quite geocentric due to the equant (an offset point, about from the Earth, which the planets move around). As the planets had variable speeds the model was not quite uniform circular motion. While the model succeeded in its intended purpose, it failed from our modern point of view in that it offered no explanations for the apparent motions. Ptolemy himself would have been well aware of these limitations of his model. The epicycles of the Moon would have meant that the Moon would vary in size by a factor of almost two as it approached the earth in its orbit. Plainly this does not happen. Ptolemy's purpose was to accurately describe and predict the locations of the planets not to explain their motion. Unfortunately, Ptolemy's empirical model was later on fined into Thomas Aquinas' blend of science and theology and incorporated into the doctrines of the Catholic Church. Empirical models are often used in science to make predictions when the full theory is not well understood. PB5111 http://youtu.be/JHB3iuLp0pg