ASTRO-110 Lecture Notes - Lecture 3: Eclipse Season, Optical Illusion, Nicolaus Copernicus
Document Summary
Penumbra: overall gradient, shadow still see the sun. Annular solar eclipse: moon isn"t always the same distance from earth, if the moon is far from earth, the top of the umbral doesn"t reach earth, cannot cover the sun (shows a ring annular) Eclipses can only happen twice a year during eclipse season": earth"s orbit around the sun and moon"s orbit around earth planes do not align/match, earth"s shadow is big compared to the moon. Motions of the planets there are 5 bright objects in the sky that look like stars but don"t behave like stars (planets because that is greek for wanderers they are not fixed like stars) Mercury and venus: retrograde motion and didn"t venture far from the sun. Second theory sun-centered (heliocentric) model: earth orbits the sun and planets orbit outside around the earth, and apparent retrograde is just a visual illusion (the different speeds of orbits of planets against the stars)
