Download Astro 120 Fall 2008: Lecture 7 - Eclipses and Early Astronomy and more Assignments Astronomy in PDF only on Docsity! Astro 120 Fall 2008: Lecture 7 page 1 • Earth and Moon Shadows • Umbra - region of total obscuration • Penumbra: region of partial obscuration • Lunar Eclipses • Happen only when FULL moon occurs at a node • Visible over entire night hemisphere • can be penumbral, partial or total • Solar eclipses: only at New Moon • length of Moon’s umbra ~ mean Earth (surface)-Moon dist • partial eclipse: (Moon’s penumbra) widely visible • total eclipse: visible only from narrow, fast eclipse track • annular eclipse: similar to total, but moon’s umbra doesn’t reach Earth Brief review of last time: Eclipses of the Sun and Moon Reading: Bennett,! Chapter 2, Section 2.4; Chapter S1, Section S1.1 ! Chapter 3, Sections 3.1-3.4 ! Chapter 4, through Section 4.4 TV Tonight: ABC (WOI-5): UFOs - Seeing is Believing? Homework 3: Due this Friday/Monday Exam 1: Thursday, October 2 Astro 120 Fall 2008: Lecture 7 page 2 Occam’s Razor: William of Occam, 1340(!) “We take as Truth the simplest explanation that fits all of the data” This is the fundamental principle of all modern science Today: The Discovery of Gravity pre-history! Greeks! Copernicus! Tycho! Kepler! Galileo! Newton Astro 120 Fall 2008: Lecture 7 page 3 Astro 120 Fall 2008: Lecture 7 page 4 The Early Days... • Prehistoric Discoveries • Motivation: Calendar = survival Cosmology = order = higher being • Ecliptic + Zodiac paths of planets and Sun • Solstice seasons • Saros cycle eclipses • Early Science: The (500 BCE - 150 CE) • spherical Earth (Pythagoras) • model of celestial motion (Aristotle) • relative dimensions of Sun, Moon, Earth (Aristarchus) Astro 120 Fall 2008: Lecture 7 page Ancient Calendars and Calculators • Ecliptic / Equinox / Eclipse marker: Stonehenge 5 Astro 120 Fall 2008: Lecture 7 page • Chichen Itza, Yucatan (Mexico): Annual “Calendar” 6 Ancient Calendars and Calculators Astro 120 Fall 2008: Lecture 7 page • Chichen Itza, Yucatan (Mexico): Annual “Calendar” 7 Ancient Calendars and Calculators Astro 120 Fall 2008: Lecture 7 page 8 • Ptolomy’s computational scheme for celestial motion • Earth -centered • Uniform circular Motion • Epicycles Philosophy + some observation culminated in
