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THIS PRESENTAION HAS BEEN RATED TG-13 TEACHERS’ GUIDANCE STRONGLY ADVISED Some Material May Be Unintelligible For Students Under 13. Intense Frames of Scientific Instruction, Analysis, Comparing and Contrasting, Description, and for Some Vocabulary. BY THE CLASSIFICATION AND RATING ADMINISTRATION © 1852 All Rights Reserved VOID WHERE PROHIBITED BY LAW PBIS ANTI-VACUITY The authorized reproduction or distribution of this copyrighted work is highly encouraged. Lethargic obtuseness is insubordinate and is discouraged by PBIS, as it may result in little or no monetary gain after secondary education or a fine of $250,000. © 1852 All Rights Reserved VOID WHERE PROHIBITED BY LAW ASTRONOMY ORBITAL MECHANICS: A History OBJECTIVES By the end of this presentation, students will be able to • Explain the origins of astronomy. • Describe four observations that show the earth is a sphere. Origins Of Astronomy As early as 2800 B.C. massive structures were constructed as calendars using star and sun positions to keep track of – when migratory birds would arrive for hunting; – when berries would ripen; – what season babies will be born; – when farmers should plant and harvest; – when to shelter livestock. Origins Of Astronomy Societies that had these structures had astrologer-priests, who observed, recorded, kept track of and announced when these events were about to take place. Some Astrologer-Priests asserted these events to be controlled by the motions of the stars. Origins Of Astronomy Some Astrologer-Priests turned the structures into temples and their announcements became religious ceremonies. – Stonehenge (Scotland) – Woodhenge (St. Louis) – Casa Grande (Arizona) – Myan Ruins (Yucatan, Mexico) – Temple of Amen-Ra (Karnak, Egypt) Origins Of Astronomy Other Astrologer-Priests tried to improve their observations, be more accurate with their records. They believed that if they could better understand these motions, they could better their predictions for these events. Origins Of Astronomy One such philosopher used records dating back 800 years and discovered a periodic cycle for eclipses. An eclipse should occur every 173 days, yielding an eclipse year every 346 days, completing the entire cycle every 223 lunar months, or 19 eclipse years (Saros Cycle). Early GREEK Astronomy Thales (624-546 B.C.) – Rejected mythological explanations for natural phenomena – Developed the Saros Cycle – Correctly predicted the solar eclipse of 585 B.C. Early GREEK Astronomy Anaximander (611-547 B.C.) – Developed a model for the cosmos – Coined the term “Celestial Sphere” – Placed the earth at the center Early GREEK Astronomy Pythagoras (540-497 B.C.) – Developed advances in geometry – Proposed a spherical earth • Viewing ships sailing over the horizon, the mast is the last to disappear. • Sailors view different constellations in the sky as they sail from south to north. Early GREEK Astronomy Philolaus (470-385 B.C.) – First proposed ten concentric spheres on which the sky, planets, moon and earth revolve around a “central fire.” Anaxagoras (500-420 B.C.) – Deduced the true nature of eclipses – Speculated that the sun was larger than all of Greece. Early GREEK Astronomy Eudoxus (408-355 B.C.) – Developed a model representing the motion of the planets with combinations of 27 rotating spheres – Each sphere pivoted on two opposing points on the next-inner sphere. Late GREEK Astronomy Aristotle (384-322 B.C.) – Proved the earth to be a sphere • Viewing the shadow of the earth on the moon during an eclipse. Late GREEK Astronomy Aristarchus of Samos (310-280 B.C.) – First to calculate and quantify distances and sizes of the earth, moon, sun, and celestial sphere. – Rejected the Geocentric view owing to the size of the bodies and the vast distances he calculated. – Values were far from accurate and lacked detail; thus, they were rejected. Late GREEK Astronomy Eratosthenes (384-322 B.C.) – First to measure the circumference of the earth. s = C_ q 360⁰ q s q Radius, R Late GREEK Astronomy Hipparchus (160-127 B.C.) – Invented and developed trigonometry. – Devised a system for categorizing stars by brightness. – Made extensive observations with great accuracy. – Catalogued over 850 stars by position and brightness Late GREEK Astronomy Hipparchus (160-127 B.C.) – First to observe the precession of the poles and explained them with eccentric circles as planetary orbits; thus… – Agreed with Aristarchus’ heliocentric view. – To avoid criticism, he explained the precession from a geocentric view using epicycles and deferents. Late GREEK Astronomy Claudius Ptolemy (A.D. 90-168) – Expanded the catalogue of Hipparchus to 1022 stars and agreed with his heliocentric conclusion. – Refined Hipparchus’ model of the Celestial sphere, which became popular until the time of Copernicus (A.D. 1500). Late GREEK Astronomy Claudius Ptolemy (A.D. 90-168) – Model of the Celestial Sphere. Epicycles – The deferents explain retrograde motion of the planets Deferents MIDIEVAL Astronomy As the Greek civilization declined and Rome captured Egypt, interest in science dwindled and died. Muhammad al Battani (c. A.D.900) – compiled tables of the positions of the sun, moon, and planets, recalculated the precession and predicted eclipses. MIDIEVAL Astronomy Arab astronomers introduced Ptolemaic model of the Celestial Sphere to European astronomers. By 1130, European astronomers understood Ptolemy’s model to be of “what is” and not of “what is seen”. MidIEVAL Astronomy King Alfonso, 1252, supported a tenyear project to calculate predicted planetary positions. The result were the Alfonsine Tables, the basis for all planetary predictions for the next three centuries Revolutionary Astronomy Nicolas Copernicus (1473-1543) – In 1504, observed a conjunction between all five known planets – something the Alfonsine Tables did not predict. – Determined the Ptolemaic model was too complex to produce reliable results. – Developed a simpler, more reliable model: Revolutionary Astronomy Nicolas Copernicus (1473-1543) – Developed a simpler model • Placed the sun at the center of the celestial sphere. • Placed the planets, including the earth, in their correct order from the sun outward. • Made the celestial sphere so big, the distances to the planets was negligible. Revolutionary Astronomy Michael Servetus – Adamantly agreed with Copernicus. – Burned at the stake in 1533. Giordano Bruno – Vigorously defended Copernicus. – Burned at the stake in 1600. Revolutionary Astronomy Tycho Brahe (1546-1601) – Catalogued nearly 800 stars, their positions and brightness. – Catalogued precise positions of the planets, moon and sun each night from 1576 – 1596. – viewed positions of seven comets – viewed a nova (new star) for 16 months. • It out shined Venus for several weeks. Revolutionary Astronomy Tycho Brahe (1546-1601) – Hired to make observations for King Frederick II of Denmark. – Built “Uraniborg” for the purpose of making very precise, naked-eye observations. – Fired by the King’s successor and forced to move to Prague to study his observations until the day he died. Revolutionary Astronomy Johannes Kepler (1571-1630) – Studied Tycho’s data after Tycho died – Tried to fit the data to many versions of the Ptolemaic model. – Found the data to fit closely to the Copernican model. – Developed 3 laws describing the motions of the planets: Revolutionary Astronomy Johannes Kepler (1571-1630) – Developed 3 laws describing the motions of the planets Plane of • Law of Ellipses – Every planet Earth’s orbit moves around the sun in an star elliptical orbit Orbital Planet (near circular Orbit Radius oval) with the Planet sun at one focus. Revolutionary Astronomy Johannes Kepler (1571-1630) – Developed 3 laws describing the motions of the planets • Law of Areas – A line drawn from the sun to a r A1 planet will star sweep out equal A1 = A2 areas of space A2 in equal times. Planet Revolutionary Astronomy Johannes Kepler (1571-1630) – Developed 3 laws describing the motions of the planets • Law of Harmony – The ratio of the cube of the average orbital radius to the square of its period is a constant. T2 = K a3 • More on this later. Revolutionary Astronomy Galileo Galilei (1564-1647) – Agreed with Aristotle’s principles of mechanics, but set out to prove them experimentally – Pointed the telescope to the stars and found evidence to prove Aristotle’s Celestial mechanics was flawed. • Viewed lines on Mars, “ears” on Saturn, moons orbiting Jupiter, spots on the sun, mountains and depressions on moon. Revolutionary Astronomy Isaac Newton (1643-1727) – Developed 3 laws to explain all motion – Developed the universal law of gravity • Proved that the force that pulls an apple to the ground is the same force that keeps the moon in orbit. • Provided the explanation for Kepler’s Laws that Kepler lacked. RENAISENCE Astronomy Edmund Halley (1656-1742) – Expanded the use of Newton’s Laws and Kepler’s Laws to comets. – Published data on 24 comets, noting that three were so similar they had to be the same comet. – Predicted it reappearance in 1758. – George Palitzsch identified the comet in its predicted position in 1758. RENAISENCE Astronomy Johann Bode (1747-1826) – Popularized a relationship between the planets and their relative distances from the sun. • Begin with a series of 4’s – one for each planet • add to each 4 the corresponding number in the sequence 0, 3, 6, 12, 24, 48, 96..., then divide the result by ten. RENAISENCE Astronomy Johann Bode (1747-1826) – Popularized a relationship between the planets and their relative distances from the sun. Planet # 1 2 3 4 5 6 7 8 4 4 4 4 4 4 4 4 + 0 3 6 12 24 48 96 192 4 7 10 16 28 52 100 196 RENAISENCE Astronomy Johann Bode (1747-1826) – Popularized a relationship between the planets and their relative distances from the sun. Planet # 1 2 3 4 5 6 7 8 4 7 10 16 28 52 100 196 10 10 10 10 10 10 10 10 Dist. = 0.4 0.7 1.0 1.6 2.8 5.2 10.0 19.6 Mer. Ven. Earth Mars Jup. Sat. RENAISENCE Astronomy Giuseppe Piazzi (1746-1826) – Discovered the “missing planet” from Bode’s Rule (1851). Its orbit was between Mars and Jupiter. – Named it Ceres. – Many others were discovered (110 by 1900), and the “missing planets” formed a ring of “minor planets”. – Now over 650,000 minor planets. RENAISENCE Astronomy William Herschel (c.1738-1822) – Discovered Uranus (1781) while making deep sky observations; called it “Georgian Star”. – Mapped the “universe” (1790). • disk-shaped • Stars at varying distances from our own • The sun was at the center. – Called the “Minor Planets” asteroids. RENAISENCE Astronomy John Couch Adams (1819-1892) – Using the data on the orbit of Uranus, applications of Newton’s Laws and discrepancies from Bodes’ Rule, predicted the existence of another planet. – Planet later discovered by Galle (1846) and was named Neptune. MODERN Astronomy JC Kapteyn (c.1910) – expanded the size of Herschel’s universe to about 55,000 ly. Harlow Shapley (c.1920) – expanded the size of Herschel’s universe to about 300,000 ly. HP Robertson (c.1924) – placed the sun away from the center of the galaxy. MODERN Astronomy Edwin Hubble (c.1925) – Proved the existence of objects beyond our own galaxy. • Viewed 45,000 other galaxies, which were at such tremendous distances away from the near-by stars. • Measured their velocities and determined them to be expanding away from a common center. MODERN Astronomy Clyde Tombaugh (c.1930) – Using the data on the orbit of Neptune, applications of Newton’s Laws and discrepancies from Bodes’ Rule, predicted the existence of another planet. • Called the planet Pluto. ASTRONOMY ORBITAL MECHANICS