ASTR 101 Lecture Notes - Lecture 3: Aswan, Almagest, Orbital Period

• School: Queen's University
• Department: Physics, Engineering Physics and Astronomy
• Course: ASTR 101
• Professor: David Alan Hanes

Document Summary

Scientific thinking is based on everyday ideas of observations and trial-and-error experiments. Many of our current systems had their roots in the achievements of ancient astronomy. Egyptian obelisk: shadows tell time of day. Ancient people of central africa (6500 bc) could predict seasons from the orientations of the crescent moon. Days of week were named for the sun, moon, and visible planets. Greeks were the first people known to make models of nature. They tried to explain patterns in nature without resorting to myth or the supernatural. Special topic: eratosthenes measure earth (c. 240 bc) Syene to alexandria distance 5000 stadia angle = 7 (cid:2875)3(cid:2874)(cid:2868) (cid:4666)(cid:1855)(cid:1870)(cid:1855)(cid:1873). (cid:1870)(cid:1872) (cid:4667)=(cid:887)000 (cid:1871)(cid:1872)(cid:1856) (cid:1855)(cid:1870)(cid:1855)(cid:1873). (cid:1870)(cid:1872) =(cid:887)000 3(cid:2874)(cid:2868)(cid:2875) . Earth at the centre for the universe. Heavens must be perfect : objects moving in perfect spheres or perfect circles. But this made it difficult to explain apparent retrograde motion of planets .