Worlds in Points of Light (Naked Eye Observations) Star-like Worlds My Background https://carleton.ca/linr/early-spring-2018-session/class-notes/ Robert Dick rdick@robertdick.ca February 28-April 4, 2018 Robert Dick, Bruce Penn., ON I have held the crescent Moon in the palm of my hand and bathed in the starlight of wonderland Path of the planets 1 Learning from light 2 Planet diversity 3 Remote sensing 4 Planetary evolution 5 Extra-solar planets 6 What to Expect Week (Naked-eye observing) (Astronomical instruments) (Planetary astronomy) (Magic instruments, intimacy) (Up-close and personal) (Check on reality) Science Fiction Philosophy Poetry Imagination Fields of Study Observations Common Sense Critical Thinking Curiosity Physics Chemistry Remote Sensing Geology The Human Condition ASTRONOMY Today Introductions Course Outline Overview of Sky (Celestial Sphere) Historical Perspective Early Astronomy Our Vision (Brightness) Vision (colour sensitivity) Lure of Naked-Eye Observing No expensive instruments Cheep past-time Simple experiments Changing patterns = changing geometry Intellectual mind-games (physics) Mathematics (algebra, calculus) Cultural insights Answers major questions (structure of the solar system, Universe) 1
Diurnal.jpg The Celestial Sphere R.A. Scale Course Starmap Declination Scale Date Scale Course Polar Maps Course Polar Map Polar Sky on March 5 Changes in Celestial Sphere Date Sky at 10 pm LST Fireball Celestial Sphere - A narrated Tour of the Night Sky - Diurnal Rotation 2
Moon s Orbit Meteors (meteorology) Independent from Ecliptic Moon is Spherical Rapid changes = close Orbit Tilted wobbles (precesses) occasional eclipses Random = uncertainty Robert Dick, Rideau Ferry, ON Starlight Theatre - Fireball, from Celestial Sphere - A Narrated Tour of the Night sky Project back to Inter-planetary orbit 400K km Shower = stream comet debris Tom Matheson, NJ Robert Dick, Baja, Mx 1991 Spherical Earth Solar Eclipse Lunar Eclipse Same Shadow Robert Dick, Rideau Ferry, ON Comets Note: Public interest No terror Orbits and origins - elongated orbits Newton s Laws Great Comet of 1680 Obscurity to prominence... then back to obscurity Robert Dick, Baja, Mx 1991 Utility of Astronomy Omens weather (clear, hazy) Navigation way-finding Time reckoning at night Geometry in motion Contemplation Astrology Importance for survival! 3
Astrology Greek Mythologies Existed before recorded history Practical Leisure Remuneration for astronomers Kept astronomy in the social consciousness The gods and wandering stars Planetoi = wandering star GREEK Hermes Aphrodite Ares Zeus Cronus Uranus Poseidon ROMAN Mercury Venus Mars Jupiter Saturn Caelus Neptune Greek Universe Ptolemaic System (Almagest) - perfect circles, - constant speeds Heavens Celestial Sphere Planets Atmosphere Earth/Mortals Depth into sky Made accurate with empirically derived data - planar solar system - deferents, epicycles, eccentrics equants Claudius Ptolemy Egypt, 2 nd C AD What they Deduced Ptolemaic System Predictive world system Philosophy-based (Aristotle) Immutable heavens Geometric purity Constant speed Circular motions Simplicity (?) Cultural Mystique Greek Discoveries Predicting the planets instructing the gods Works of Aristotle 1600-yrs religious dogma Heresy to question: - Earth-centred universe - circular and constant motion Hipparchus (190-120 BCE) ( Polymath ) Recording observations Accurate star catalogue to replace older one precession Others Accurate measures of planet motion - geometry - brightness implies distance - epicycles,... 4
What They Taught Us Greek Experiment There are bright wandering objects They are constrained to narrow band (ecliptic) Their motion is smooth and predictable They vary in distance from us (brightness) There are two sets opposition, non-opposition [outer] [inner] Eratothenes 850 km/0.02 = 42,500 km [40,100 km] Diameter of Earth 200 BCE Conjunctions Oppositions 1/2 Aristarchus Moon Distance = Earth Lat. Earth Radius Star Angle D M = Lat. x E R = 5 x 6300 km * 1/12 = 380,000 km Aristarchus BCE 310.230 276 194 BCE Eratothenes Moon s Distance 300 BCE Historical Perspective We start with the points of light. How much can our unaided eye show us (ancient and renaissance eras)? What observations can we make to confirm our present world view (stargazing)? Position, Brightness,... Motion Visual Techniques Record keeping - preservation of knowledge (Hipparchus 190-120 BCE) Naked Eye - qualitative, cultural narratives (oral histories) - accuracy limited to ~1/2 degree (Moon) Visual Instruments (Sextans/Octants ~1000 ADE) - sights to fix eye s position in instrument - accuracy ~1/30-deg (~2 arc minutes (1600 ADE) 5
Arab Astronomy Date Time Stars Sextants (size = precision) Sun Based on Ptolemaic System - practical, unifying Translated Almagest to Arabic Samarkand Observatory and Sextant 15 th Century Diffused across Africa and southern Europe Enabled translation into Latin for posterity Astrolabe 220 BCE Present Visual Precision Natural Light Levels at Night Pupil diam. = 6mm Sextant arm = 1m 0.34 Better sight ~ 0.5mm 0.03 1/10 th brightness to read a book is natural limit (silvery grey) Scotopic 1/1000 th = walk-about at night - a practical limit - Photopic Tycho Brahe s Sextant 17 th Century 1m 1m 1cd 20,000 cd/m 2 Limits to Vision Brightness - Colour - Resolution Brightness Moon is bright, but ~ 1/1000 streetlight (1-4 million cd/m 2 ) Luminance Moon 6,000 cd/m 2 Moon Candle 20,000 Venus 15,000 Mars 4,000 Jupiter 800 Sun 3x10 9 1m LEDs Interesting Information Bronowski, Jacob - Assent of Man www.youtube.com/watch?v=dfgngul78mu (A still-remarkable 13-part BBC Series) Pannekoek, A. - A History of Astronomy ( Dated interpretation of history) Interscience, 1961 6