The Origin of Modern Astronomy

1. 0 The Origin of Modern Astronomy Chapter 4

2. 0 Guidepost The previous chapters gave you a modern view of what you see in the sky, and now you are ready to understand one of the most sweeping revolutions in human thought: the realization that we live on a planet. In this chapter, you will discover how astronomers of the Renaissance overthrew an ancient theory and found a new way to understand Earth. Here you will find answers to four essential questions: • How did the ancients describe the place of the Earth? • What is the real contribution of Islamic Astronomy? • How did Copernicus change the place of the Earth? • Why was Galileo condemned by the Inquisition? • How did Copernican astronomers solve the puzzle of planetary motion?

3. 0 Guidepost (continued) This astronomical story will introduce you to the origin of modern astronomy, and it will help you answer an important question about science. • How do we know? How do scientific revolutions occur?

4. 0 Outline 1 I. The Roots of Astronomy A. The Astronomy of Greece B. The Ptolemaic Universe II. Islamic Astronomy A. Growth of Islamic Astronomy B. Major Schools of Astronomy (Baghdad, Cairo, Andalusia, Maragha, Samarqand) C. Instruments, Observatories III. The Copernican Revolution A. Copernicus the Revolutionary B. De Revolutionibus C. Galileo the Defender

5. 0 Outline 2 IV. The Puzzle of Planetary Motion A. Tycho the Observer B. Tycho Brahe's Legacy C. Kepler the Analyst D. Kepler's Three Laws of Planetary Motion

6. 0 I. The Roots of Astronomy

7. 0 Ancient Greek Astronomers (1) • Unfortunately, there are no written documents about the significance of stone and bronze age monuments. • First preserved written documents about ancient astronomy are from ancient Greek philosophy. • Greeks tried to understand the motions of the sky and describe them in terms of mathematical (not physical!) models.

10. 0 Ancient Greek Astronomers (2) Models were generally wrong because they were based on wrong “first principles”, believed to be “obvious” and not questioned: • Geocentric Universe:Earth at the Center of the Universe • “Perfect Heavens”:Motions of all celestial bodies described by motions involving objects of “perfect” shape, i.e., spheres or circles Greeks assumed the Earth was not moving because they did not observe parallaxes in the sky. (Animation - 1)

11. Stellar Parallax

12. 0 Later refinements (2nd century B.C.) • Hipparchus: Placing the Earth away from the centers of the “perfect spheres” • Ptolemy: Further refinements, including epicycles

13. 0 Epicycles Introduced to explain retrograde (westward) motion of planets (Animation - 2) The Ptolemaic system was considered the “standard model” of the Universe until the Copernican Revolution.

14. II. Islamic Astronomy

15. 0 Islamic Astronomy • Major impetus came from religious observances: Presented an assortment of problems in mathematical astronomy. • Religious customs presenting problems in spherical astronomy: • Crescent Moon: start of Islamic month • Direction of Qibla: praying toward Mecca • Proper time for the five daily prayers.

17. Golden Names, Forgotten Golden Civilization….. Al-Abhari, Adnan Al-Ainzarbi, Ali Ibn Issa, Ibn Amajur, Al-Amili, Al-Ashraf, Al-Asturlabi, Ibn Bajjah, Al-Bakhnayqi, Al-Balkhi, Banu-Mussa, Abu’l Barakat, Ibn Al-Fasi, Al-Battani, Al-Biruni, Al-Bitruji, Al-Jaghmayni, Al-Farghani, Al-Farisi, Al-Fasi, Al-Fazari, Abbas Ibn Firnas, Habash Al-Hasisb, Al-Hajjaj Ibn Yussuf, Al-Hamdani, Hamid Ibn Ali,Ibn al-Haytham, Ibnrahim Ibn Sinan, Jabir Ibn Aflah, Al-Jawahri, Al-Jayani, Ibn al-Jazuli, Al-Kabisi, Qadhi Zadeh Al-Rumi, Al-Karari, Al-Kashi, Al-Katibi, Al-Kawashi, Al-Katibi, Al-Khalili, Al-Haraki, Al-Khayyami, Al-Khazin, Al-Khazini, Al-Khujandi, Al-Khwarizmi,Al-Kuhi, Al-Kushdji, Kashyar Ibn Labban, Ibn al-Al-Abudi, Al-Maghribi, Al-Mahani, Ibn Al-Majdi, Al-Majriti, Al-Maksi, Al-Marrakushi, Abu-Ma’shar, Al-Misri, Al-Mizzi, Abu Nasr, Al-Nayrizi, Qaysar, Ibn Al-Qunfudh, Al-Qusantini, Ibn al-Raqqam, Ibn al-Rashidi, Al-Razi, Ibn-Rushd, Ibn al-Saffar, Al-Saghani, Ibn Sa’id, Abu’l Salt, Ibn Sina ,Ibn al-Shatir, Al-Samarqandi, Ibn Al-Samh, Sinad Ibn Ali, Ibn al-Sarraj,Al-Shirazi, Al-Sijri, Sinan Ibn Thabit, Al-Sufi, Thabit Ibn Qurrah,Al-Tusi, Ulugh Begh, Umar Ibn al-Farkhan, Abu al-Uqul, Al-Urdi, Abu’l Wafa, Yahya, Yaqub Ibn Tariq, Ibn Yunus, Al-Zarqali,

18. 0 Major Schools of Islamic Astronomy (1) • Baghdad • Started from the reign of Caliph al-Mansur (754-775) • Under Harun ar-Rashid and al-Ma’mun, the school of Baghdad produced its most important works. • Old theories were revised, Ptolemy’s errors were rectified, and the astronomical tables of the Greeks corrected. • Most Important Astronomical Works: • Detailed study of the exact duration of the solar year (al-Battani) • Prediction of solar and lunar eclipses (al-Battani) • Theory of the lunar crescent visibility. • Al-Battani’s Zij, considered as the most important astronomical works between the time of Ptolemy and that of Copernicus.

19. 0 Major Schools of Islamic Astronomy (2) • Cairo: • Founded by the illustrated Ali Ibn Yunus, inventor of the pendulum, and the solar quadrant. • Most Important Astronomical Works: • “Al-Hakimi Zij”, astronomical tables edited by Ibn Yunus, used in Cairo into the 19th century. • More than 100 solar observations and planetary conjunctions are reported in the Hakimi Zij. • Optical treatises of Hassan Ibn al-Haytham, which served as the basis for the works of Roger Bacon and Kepler.

20. Summary of Past Lecture • Many cultures around the world observed the sky and marked important alignments • But, having no written language, left no detailed records of their astronomical beliefs. • Greek astronomy, derived in part from Babylon and Egypt, is better known because written documents have survived. • Greek astronomers believed firmly in two principles: • Geocentric universe: Earth center of the whole universe • Perfect heavens: Heavens must be made of spheres in uniform motion • Ptolemy Universe: Added epicycles to account for the retrograde motion

21. Muslim astronomers: • Revised old theories. • Rectified Ptolemy’s errors. • Corrected the astronomical tables of the Greeks. • School of Baghdad: • Best work: Al-Battani’s Zij, considered as the most important astronomical works between the time of Ptolemy and that of Copernicus. • School of Cairo: • Best work: “Al-Hakimi Zij”, astronomical tables edited by Ibn Yunus, used in Cairo into the 19th century.

22. Think and Answer…(Animation - 2) • Ptolemy's model of the universe a. was heliocentric. b. included elliptical orbits. c. contained epicycles. d. all of the above 2. The purpose of using epicycles to explain the motion of the planets in the night sky was to account for a. prograde motion. b. Mercury and Venus’ limited angular distance from the Sun. c. retrograde motion. d. non-uniform speed of the planets in their orbits.

23. Scientific Argument…. (Animation - 1) • Why did the Greeks believed firmly in the geocentric system?

24. 0 Major Schools of Islamic Astronomy (3) • Maragha: • Started with Nasir al-Din al-Tusi by the construction of the Maragha observatory in 1259. • Responsible for the revival of Islamic science in all fields. • Astronomical activities influenced the observatories of Samarqand and Istanbul, and also those in the West. • Most Important Astronomical Works: • Compilation of the “Ilkhani Zij” displaying the results of 12 years of observations at the Maragha observatory.

25. 0 Major Schools of Islamic Astronomy (4) • Samarqand: • Started with the foundation of a “Madrasa” by Ulugh Begh in 1420. • Lecturers included the most famous Muslim mathematicians and astronomers (Kadi Zada and al-Kashi) brought under one roof. • Thousands of students were lectured and were assisted by hundred of scientists. • An Observatory was built to fulfill the task of completing the educational needs of the students in astronomy. • Most Important Astronomical Works: • Compilation of Ulugh Begh’s Zij displaying the results of 20 years of observations at the Samarqand observatory. • Yearly movements of Saturn, Jupiter, Mars, and Venus were known to within the limits of two to five seconds of those of modern times.

26. C. Instruments, Observatories

27. Sundials

28. A huge armillary sphere

30. Huge armillary sphere (Ibn Battutah Mall – Dubai)

31. Maragha Observatory

32. Ruins of the entrance of the Samarqand Observatory

34. Astrolabe

35. Quadrant

39. III. The Copernican Revolution

40. 0 The Copernican Revolution Nicolaus Copernicus (1473 – 1543): Heliocentric Universe (Sun in the Center)

42. 0 Copernicus’ New (and Correct) Explanation for the Retrograde Motion of the Planets Retrograde (westward) motion of a planet occurs when the Earth passes the planet. (Animation - 3) This made Ptolemy’s epicycles unnecessary.

43. 0 Galileo Galilei (1594 – 1642) • Invented the modern view of science: Transition from a faith-based “science” to an observation-based science • Greatly improved on the newly invented telescope technology, (But Galileo did NOT invent the telescope!) • Was the first to meticulously report telescope observations of the sky to support the Copernican Model of the Universe

44. 0 Major Discoveries of Galileo • Moons of Jupiter (4 Galilean moons) • Rings of Saturn (What he really saw)

45. 0 Major Discoveries of Galileo (2) • Surface structures on the moon; first estimates of the height of mountains on the moon

46. 0 Major Discoveries of Galileo (3) • Sun spots (proving that the sun is not perfect!)

47. 0 Major Discoveries of Galileo (4) • Phases of Venus (including “full Venus”), proving that Venus orbits the sun, not the Earth!

48. IV. The Puzzle of Planetary Motion

49. 0 Tycho Brahe (1546 – 1601) • High precision observations of the positions of stars and planets • Measurement of the nightly motion of a “new star” (a supernova) showed no parallax • Evidence against Aristotelian belief of “perfect”, unchangeable heavens

50. 0 Tycho Brahe’s Legacy New World model • Still geocentric (Earth in the center of the sphere of stars) • Sun and Moon orbit Earth; Planets orbit the sun.