Lecture 2

Lecture 2 - Announcements – • TAs – introduction • Your TA contact info can be found on WebCT site under course content – TA Assignment

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Unformatted text preview: Announcements – Jan 10, 2011 • TAs – introduction • Your TA contact info can be found on WebCT site under course content – TA Assignment folder • Also, be sure to check WebCT course discussion board (discussions tab in the LHS of browser) and announcements on WebCT • Clicker questions for practice this class – next class begin counting for marks Chapter 2: The Science of Life in the Universe Greeks and Early Science • Key point : Greeks (circa 500 BC) started looking for rational explanations (this framework of explanations we call models) of natural phenomena which are understandable and which are consistent (at least somewhat) with observations • The beginnings of modern science! • Early speculation about ET life not grounded in science Greeks and Early Science - II • Greeks have mathematical sophistication together with geometry – Apply this tool to understanding new ideas • Greeks challenge new ideas proposed about the natural world – Crucial underpinning of the modern scientific method • Recognized that observations had to be the final “arbitrator” of ideas put forth to explain nature Greeks and ET life • Greeks agree that observations suggest the world is made up of four elements: fire, water, earth and air • Greeks have two schools of thought about how this applies to the Universe: 1. Atomists : all four elements available as an infinite number of indivisible particles (called atoms) making up the entire Universe 2. Aristotelians : four elements make up the World (Earth), but the heavens consist of a distinct fifth element called aether. Atoms might or might not be involved Greeks and ET life - II • Atomists believed in a universe of “infinite” numbers of atoms – Thus whatever created the Earth must occur infinite times over elsewhere and thus life is everywhere – Parallels with some modern multiverse theories • Aristotelians believed each element had its own natural place and motion and this was unique – More than one world would imply more than one natural place which is not possible – Thus no ET life and Earth is unique! Emergence of Science - Early views of the sky based on observations • Stars are fixed but some objects “wander” (planets, moon and sun) • Greeks and round Earth – Departing ships : land disappears starting at lowest points – Constellations/stars visible differ from place to place • Eratosthenes calculates approximate size of the Earth – Based on variation in altitude of sun at noon from two cities of known separation – Gets value near 6259 km – very close to modern 6378 km 7 5 k m Putting in the Numbers… • Distance to Aswan (D) – 785 km • tan Ө =d/H – Ө = 7.2º • tan Ө = D/R R=D/tan Ө – = 785km/0.1263 =6214 km • Actual radius = 6378 km ! The Earth as the center of it all • Greeks assume Earth is center of Solar System • To account for motion of planets (particularly retrograde motion) employ deferents and epicycles • Approximately correct; does not reproduce motion of planets with much accuracy far into the future deferent Copernicus and the heliocentric...
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This note was uploaded on 03/08/2011 for the course ASTRO 2021 taught by Professor Brown during the Spring '10 term at UWO.

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Lecture 2 - Announcements – • TAs – introduction • Your TA contact info can be found on WebCT site under course content – TA Assignment

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