Developing Perspective the History and Tools of Astronomy Introduction to the Course Tour of the Universe our Earth Moon individual planets the solar system nearby stars and star clusters the Milky Way galaxy the Local Group and galaxy clusters and superclusters know their sizes in ascending order and their general appearance The Scale of the Cosmos 13 20 billion years age of the universe relationship between speed distance and time distance rate x time speed of light c 3x105 km sec astronomical length scales Astronomical Unit A U avg distance between Earth and Sun Light Year l y distance traveled by light in one year 1 5x108 km 1013 km scientific notation and powers of Ten 1012 1 000 000 000 000 trillion tera 109 1 000 000 000 billion giga 106 1 000 000 million mega 105 100 000 104 10 000 103 1000 thousand kilo 102 100 101 10 100 1 10 1 0 1 10 2 0 01 centi 10 3 0 001 milli 10 4 0 0001 10 5 0 00001 10 6 0 000001 micro 10 9 0 000000001 nano 10 10 0 0000000001meter Angstrom be able to do calculations using scientific notation Increasing length scales x100 each step 1 mm size of an ant 10 cm size of a flower 10 m size of a boxing ring or 10 yards on a football field 1 km several dozen city blocks or 5 8 of a mile 100 km distance from here to Panama City Beach for spring break 10 000 km almost the size of the Earth 1 000 000 km just over the diameter of the Moon s orbit 108 km 2 3 the radius of the Earth s orbit light takes 5 minutes to cross 1010 km essentially the size of the solar system 1012 km the Sun a tiny dot mostly empty space 1014 km nearest half dozen stars 10 light years across 1016 km small fragment of the Milky Way galaxy 1000 stars 1018 km entire galaxy 100 000 light years 100 billion stars 1020 km much larger than the Local Group of galaxies 1022 km one billion light years incl most of the observable universe Quasars 1024 km 100 billion light years no light has yet traveled that far well beyond the edge of the visible universe The Celestial Sphere the Sky and the Calendar What you need to know features of the celestial sphere definition of the celestial equator poles meridian zenith nadir etc definition of angular diameter ecliptic zodiac the reasons for the season cause and appearance of eclipses and phases of the moon NOTE THE DIFFERENCES local coordinate system based on the observer s horizon altitude azimuth and a global coordinate system fixed to the celestial sphere and thus also to the stars right ascension declination ALTITUDE 0 horizon to 90 straight up AZIMUTH 0 north to 360 around horizon eastward LATITUDE North south position on Earth South Pole 90 Equator 0 North Pole 90 In the northern hemisphere Latitude is equal to the altitude height above the horizon of the North Celestial Pole position of Polaris LONGITUDE East west position on the Earth 180 west to 180 east 0 through Greenwich England Longitude can be obtained by knowing the precise time that a star of known right ascension passes across the local meridian line and comparing that withe the exact time that the same star crossed the Greenwich meridian ZENITH straight up direct overhead NADIR straight down directly under your feet MERIDIAN curved arc on the celestial sphere through North Pole Zenith and South Pole DECLINATION North south position on the celestial sphere fixed to the sphere 90 to 90 Celestial South Pole 90 Celestial Equator 0 Celestial North Pole 90 RIGHT ASCENSION East west position on the celestial sphere fixed to the sphere 0hr to 24hr NOTICE the relative elevation of the Sun at noon at different times of the year as it moves along the ecliptic ECLIPTIC ZODIAC path of the Earth s orbit around the Sun apparent path of the Sun across the sky The Zodiac is that band of constellations through which the ecliptic passes and through which all the planets with orbits near the ecliptic move Reasons for the Seasons VERNAL EQUINOX SUMMER SOLSTICE AUTUMNAL EQUINOX WINTER SOLSTICE Know what each is PRECESSION 25 800 year cycle of the wobble of the Earth s rotation axis NCP now pointed at Polaris but in 3000 B C it was pointed at Thuban Draconis and will continue to sweep across the sky NOTICE the relative positioning of the Sun Earth and Moon and the planets as they move through these motions ECLIPSES Solar Lunar Umbra Penumbra PLANETARY MOTION Direct and Retrograde The Night Sky Constellations and Motions Magnitude Scale Constellations Magnitude Scale Motion Archeoastronomy and Ancient Sky Viewers The Ancients were keen observers of the sky and guided their lives by the cycles they saw cycles of day and night rotation of the earth cycles of the tides and fishing and commerce relative position of the Earth Moon and Sun and the cycles of days and months cycles of the months and women s monthly cycles cycles of the seasons and the planting and harvesting of crops etc and with good reason Life throughout history has nearly always been at or near the subsistence level right at the boundary between life and death between survival and catastrophe work when it s light rest when it s not pragmatism as a boatman you could only get in and out of most harbors safely at high tide and wanted to be where the fish were when they were running further it was always important not to run ships aground on shallow shoals All these depended on knowing the cycles of the tides plant and harvest crops in favorable seasons if you plant too soon or too late your crops will fail and you will all die but superstition grew up around all these activities These were life and death matters to them This lead to Ancient religions examples Egyptian planting cycles set to the co rising of Sirius with the Sun Stonehenge Mayans American Indian stone circles etc the ancients were exceptionally keen observers of the sky set very precise geometrical observatories where they set their calendars by aligning with the stars and motions of the planets and the Sun Astrology Many careful scientific studies have shown no correlation between astrological birth sign and events or patterns in people s life the Copernican Revolution Models of the Universe Geocentric Model of the Universe Claudius Ptolemius Greek scholar and librarian living in Alexandria Egypt 140 AD Earth centered based on the Aristotelian world view that the world followed patterns of symmetry and truth and beauty tied very closely to the Christian view of the centrality and importance of Man in the universe perfectly circular orbits cycles upon cycles upon cycles epicycles and