01 Greeks Matter, Motion, Universe.pdf

Greeks on Matter, Motion, and the Universe SCIENCE 10: Probing the Physical World University of the Philippines Baguio Christian P. Crisostomo, Ph.D. SCIENCE 10: Pr...

Greeks on Matter, Motion, and the Universe SCIENCE 10: Probing the Physical World University of the Philippines Baguio Christian P. Crisostomo, Ph.D. SCIENCE 10: Probing the Physical World Dr. Christian P. Crisostomo 1 University of the Philippines Baguio Leon Lederman: Visitors from Twilo (a.k.a. the story of the invisible soccer ball) 2 Seven Sentences 1. The Earth is not the center of the universe (Copernican Astronomy) 2. The universe is a mechanism run by rules (Newtonian mechanics and causality) 3. Energy is what makes it go (the concept of energy) 4. Entropy tells it where to go (entropy and probability) 5. The facts are relative but the law is absolute. (relativity) 6. You can’t predict or know everything (quantum theory and the end of causality) 7. Fundamentally, things never change (conservation principles and symmetry) 3 Seven Sentences 1. The Earth is not the center of the universe (Copernican Astronomy) 4 Greeks, Matter, Motion, and the Universe 5 Questions for the Next Two Weeks How did we come to realize that the Earth is not the center of the universe? How did we come to adopt the view that the universe is a mechanism? 6 Our story begins with the ancient Greeks... Why talk about the Greeks? Why talk about the Greeks? They got some things right … Why talk about the Greeks? They got some things right … and many things wrong … Why talk about the Greeks? They got some things right … and many things wrong … But they started asking the right questions. Greek View of Matter, Motion, and the Universe Natural Philosophy and the Role of Mathematics Matter Motion The Universe 12 Natural Philosophy and the Role of Mathematics 13 Greece 7th Century B.C. The Universe is a rational place, with natural laws that can be figured out. 14  Natural Philosophy An attempt to develop a consistent set of “natural laws” to explain physical phenomena without reference to supernatural causes / beings. 15 Plato – Mathematical symmetries as the language of universal design and harmony. Source of images http://www.math.technion.ac.il/~rl/pics/plato.jpg http://myhero.com/images/writer/plato/plato.jpg 16 Plato – Mathematical symmetries as the language of universal design and harmony. Source of images http://www.math.technion.ac.il/~rl/pics/plato.jpg http://myhero.com/images/writer/plato/plato.jpg 17 The Greeks were guided by a paradigm that was first articulated by Pythagoras (lived c569--475 B.C.E., picture on left) before Socrates' time. A paradigm is a general consensus of belief of how the world works. It is a mental framework we use to interpret what happens around us. It is what could be called ``common sense''. The Pythagorean Paradigm had three key points about the movements of celestial objects: The planets, Sun, Moon and stars move in perfectly circular orbits; The speed of the planets, Sun, Moon and stars in their circular orbits is perfectly uniform; The Earth is at the exact center of the motion of the celestial bodies. Source of image: http://sid.at/hs-strassburg/images/pythagoras.jpg http://platea.cnice.mecd.es/~macruz/mente/pythagoras.jpg 18 1, 3, 6, 10 … 19 1, 4, 9, 16 … 20  http://en.wikipedia.org/wiki/Pythagoreanism a2 + b2 = c2 21 Some Questions asked by the Greeks What is the Universe made of? What is the nature of motion? 22 Features of a Good Theory (Greek View) Logically sound All ideas consistent with each other Plausible results 23 Features of a Features of a Good Theory Good Theory (Greek View) (Modern View) Logically sound Logically sound All ideas consistent with each other All ideas consistent Plausible results with each other Quantitative Predictions Plausible results Repeated Comparison with observations and experiments 24  Domains and Elements (Greeks) Fire Sublunar/Terrestrial Domain (temporal and imperfect objects Air Water Universe Supralunar/Celestial Domain Earth (eternal and perfect objects) Element = Aether / Quintessence 25  Types of Motion (Greeks) Alteration Terrestrial Natural / Vertical Motion Horizontal / Violent Celestial (uniform + circular) 26 Celestial Motion 27 Diurnal Motion - daily motion of stars and other objects/bodies across the sky - this motion is due to the rotation of the Earth from west to east 28 5 hours of star trails in Iran 29 Annual Motion 30  Annual Motion-Sun 31  Annual Motion of the Sun Analemma = Figure 8 – like annual path of the sun Analemma photo taken from 1998 to 1999 from Bell Laboratories, Murray 32 Hill. Greeks guided by a paradigm first articulated by Pythagoras (c569--475 B.C.E) before Socrates' time. Key points about the movements of celestial objects: 1) The planets, Sun, Moon and stars move in perfectly circular orbits; Source of image: http://sid.at/hs-strassburg/images/pythagoras.jpg http://platea.cnice.mecd.es/~macruz/mente/pythagoras.jpg 33 Greeks guided by a paradigm first articulated by Pythagoras (c569--475 B.C.E) before Socrates' time. Key points about the movements of celestial objects: 1) The planets, Sun, Moon and stars move in perfectly circular orbits; 2) The speed of the planets, Sun, Moon and stars in their circular orbits is perfectly uniform; 34 Source of image: Greeks guided by a paradigm first articulated by Pythagoras (c569-- 475 B.C.E) before Socrates' time. Key points about the movements of celestial objects: 1) The planets, Sun, Moon and stars move in perfectly circular orbits; 2) The speed of the planets, Sun, Moon and stars in their circular orbits is perfectly uniform; 3)The Earth is at the exact center of the motion of the celestial bodies. Source of image: 35 http://sid.at/hs-strassburg/images/pythagoras.jpg http://platea.cnice.mecd.es/~macruz/mente/pythagoras.jpg Some Things that the Greeks Got Right 36 Some Things that the Greeks Got Right Precession of the Equinoxes North Ecliptic Pole North Celestial Pole North Celestial Pole North Ecliptic Pole Rotate Eastward Precess Westward 2000 AD 15000 AD 37 Some Things that the Greeks Got Right Earth is spherical – based on experimental evidence 38 39 40 Eratosthenes Experiment 41  Perigee Apogee Apogee and Perigee of the Moon Apogee is the farthest point from the earth. Perigee is the closest point to the earth and it is in this stage that the moon appears larger. 42 43 44 45 How much time between 1st Quarter and Last Quarter? How much time between Last Quarter and 1st Quarter? 46 How much time between 1st Quarter and Last Quarter? 13 DAYS 17 HOURS 28 MINUTES How much time between Last Quarter and 1st Quarter? 15 DAYS 23 HOURS 55 MINUTES 47 Retrograde Motion 48 Retrograde Motion Retrograde motion of Mars in 2005 Astrophotographer Tunc Tezel created this composite by superimposing images taken on 35 different dates, separated from each other by about a week. 49 Greeks Got Some Things Right Diurnal and Annual Motion Hipparchus: precession of the equinoxes, systematic recording of observational astronomy Earth is spherical Eratosthenes: Good estimate for the size of the Earth Time between 1st Quarter and Last Quarter not the same as time between Last Quarter and 1st Quarter Retrograde Motion 50 Greek Models of the Universe 51 Greeks guided by a paradigm first articulated by Pythagoras (c569--475 B.C.E) before Socrates' time. Key points about the movements of celestial objects: 1) The planets, Sun, Moon and stars move in perfectly circular orbits; 2) The speed of the planets, Sun, Moon and stars in their circular orbits is perfectly uniform; 3)The Earth is at the exact center of the motion of the celestial bodies. Source of image: http://sid.at/hs-strassburg/images/pythagoras.jpg http://platea.cnice.mecd.es/~macruz/mente/pythagoras.jpg 52  Plato: “Allegory of the Cave” 53 From Great Dialogues of Plato (Warmington and Rouse, eds.) New York, Signet Classics: 1999. p. 316. Plato: “Saving the Appearances” Observed motion = combinations of uniform circular motion Task for future Philosophers: Explain the observed motion of the heavenly bodies in terms of combinations of uniform circular motions. 54 Celestial Sphere 55  Greek View of the Universe Geocentric theory of the universe “Earth-centered universe” 56  Greek View of the Universe Geocentric theory of the universe “Earth-centered universe” Early Greek Universe : Earth + celestial spheres (Eudoxus, Aristotle) 57 58 Eudoxus (Homocentric Model) 59  Eudoxus (Geocentric Model) Moon:1+2 Sun:1+2 Venus:1+3 Mercury:1+3 Mars :1+3 Jupiter:1+3 Saturn:1+3 Stars: 1 TOTAL: 27 SPHERES 60  Aristotle’s Model Problem with Eudoxus: “Intelligences” etc. Introduced: Prime Mover + 28 other spheres (gear-like mechanism) 61 Problems with Aristotle’s Model Can’t Explain: Change in apparent size of moon Change in brightness of the planets 62  Greek View of the Universe Geocentric theory of the universe “Earth-centered universe” Early Greek Universe : Earth + celestial spheres (Eudoxus, Aristotle) Ptolemy’s Universe : Additional devices to account for actual observations. 63  Greek View of the Universe Geocentric theory of the universe “Earth-centered universe” Early Greek Universe : Earth + celestial spheres (Eudoxus, Aristotle) Ptolemy’s Universe : Additional devices to account for actual observations. 64 Minority View: Aristarchus (310-230 B.C., Greek) - the Sun is in the center of the universe -theory considered too radical - note that he was 1,750 years ahead of Copernicus Source of image http://physics.unr.edu/grad/welser/astro/astronomers.html 65 Next Meeting: Competing Models of the Universe Aristotle vs. Ptolemy Aristarchus vs. Copernicus Ptolemy vs. Copernicus I vs. Copernicus II 66