ASTR/GEOL 3300: ET Life • Logistics: – Your first day? Pick up a syllabus, overview, etc. – www.boulder.swri.edu/~kwalsh/ASTR3300 • News: – Homework #1 next week • Plan for Today: – Scale of the Universe – Our place • Next time: Forming Stars and Planets Rebecca’s Office Hours • Office: E122 2:00-4:00 Monday and Wednesday Preliminary HW1 results Question Yes No Mars 22 33 Solar System 35 20 Galaxy 46 9 Universe 48 7 The Greeks Thales – First Greek Astronomer • ~600 BC • Actually asked questions: “What is the Universe made of” • Predicted an eclipse • Also.. Anaximander Pythagoras and Erastothenes Retrograde motion • http://mars.jpl.nasa.gov/allaboutmars/ nightsky/nightsky04/ Ptolemy What did the Greeks know • The planets, Sun and Moon move across the sky, – The Sun moves at a very regular rate, but the line it follows varies with season – The Moon moves at regular rate, and the line it follows is much more regular – Some planets always move the same direction (W-E), – Though others sometimes backtrack-retrograde motion • There were no tools capable of measure absolute sizes, or precise positions Copernicus • FINALLY…. Tycho SN 1572 Kepler Kepler’s 2nd Law Galileo Newton’s Principia • Explained general laws of motion – from which Keplers laws of planetary motion are natural consequences Scale of the Universe: Powers of 10 Scientific notation: • 101 = 10 • 102 = 100 • 103 = 1000 • 106 = 1,000,000 • 109 = 1,000,000,000 • 1011 = 100,000,000,000 • 100 = 1 • 10-1 = 0.1 • 10-2 = 0.01 • Also, common notation: • 1e9 = 109 Eames chair Powers of Ten • http://www.youtube.com/watch? v=0fKBhvDjuy0 • http://www.youtube.com/watch? v=vRjGarICal4&feature=related Cosmic Voyage Youtube comments Units • 1 km = 0.62 miles • 1 AU = 150 million km (1.5e8 km) – Average Earth-Sun distance • 1 ly =10 trillion km (10e12 km) – Distance light travels in 1 year – 63,241 AU – • 1 parsec = 3.26 lightyear – 31 trillion km or 19 trillion miles (19e12) Scales and Distances • Here to 28th Street @ Colorado Avenue • If that equals the distance from Earth to about where Pluto is: (5.916 × 109 km = distance from here to Pluto!) • Then the closest Sun-like star (α Cent.)*, which is 4.2 ly away (4.2 * 9.46×1012 km = 39.7×1012 km) would be: • 39.7×1012 km/5.916 × 109 km= 6,713 times farther away than Pluto • Distance from here to 28th is approx. 0.25 km, so: 6713*0.25 = 1,678 km or about the distance to Illinois (Although there are probably some dwarf stars in the neighborhood as well as LOTS of other things like ‘plutons’, comets and the like). Our Place in the Cosmos Our Milky Way Galaxy: ~1011 Stars Ghez @ UCLA The Universe: ~1011 Galaxies Olbers Paradox • If the Universe is infinite, static and filled uniformly with stars, then every line of sight will end with a star, and the sky will be perfectly light Next Tuesday • We will start into Stellar Evolution & Planet Formation (Chapter 3 in the book) • We will start getting more substantial Homeworks. Catholic Church, Galileo, Guy Consomango and Stephen Colbert • http://www.colbertnation.com/the-colbert- report-videos/257718/december-01-2009/ gold--frankincense-and-mars---guy- consolmagno .