NATS 1880 Lecture Notes - Lecture 6: Spherical Earth, Geocentric Model
2 Nov 2017
School
Department
Course
Professor
Document Summary
The geocentric model of the greeks consisted of a spherical earth at the centre of the universe surrounded by a celestial sphere. Eratosthenes (276-195 bc) determined the diameter of the earth about 240 bc at a good accuracy. Also names of days of the week are effected by names of sun, moon and 5 known planets (sun -> sunday) An observation that challenge geocentric theory was suggesting that planets not move in a regular pattern across sky. Normally planets move eastwards, however suddenly, for weeks to months, the planets move westwards. The geocentric model of the universe developed by ptolemy in about a. d. 150. He had to use only circles to represent geocentric model, and the problem was if everything was circle then planets should not change direction. This method was enough accurate to remain in use for 1500 years. Aristarchus (310-230 bc) suggested a sun centred view of the universe and planets move around the sun with different speeds.
