Scientific Revolutions: Historical Perspective

1. Scientific Revolutions: Historical Perspective  Copernicus and the Heliocentric World

2. Nicolaus Copernicus (1473-1543) TychoBrahe(1546-1601) Johannes Kepler (1571 - 1630) Galileo Galilei (1564 - 1642) Issac Newton (1643 - 1727)

4. 1543 Nicolaus Copernicus (1473-1543) De revolutionibusorbiumcoelestium Andreas Vesalius (1514-1564) De humanicorporisfabrica

5. 1543 Andreas Vesalius (1514-1564) De humanicorporisfabrica

6. 1543 Nicolaus Copernicus (1473-1543) De revolutionibusorbiumcoelestium

10. 1543 De revolutionibus orbium coelestium(על הסיבובים של הגופים השמימיים) Commentariolus ~1514 (1878) • The center of the earth is not the center of the universe, but only of gravity and of the lunar sphere. • All the spheres revolve about the sun as their mid-point, and therefore the sun is the center of the universe. • The ratio of the earth's distance from the sun to the height of the firmament is so much smaller than the ratio of the earth's radius to its distance from the sun that the distance from the earth to the sun is imperceptible in comparison with the height of the firmament.

11. 1543 De revolutionibus orbium coelestium(על הסיבובים של הגופים השמימיים) Commentariolus ~1514 (1878) • Whatever motion appears in the firmament arises not from any motion of the firmament, but from the earth's motion. The earth together with its circumjacent elements performs a complete rotation on its fixed poles in a daily motion, while the firmament and highest heaven abide unchanged. • What appears to us as motions of the sun arises not from its motion but from the motion of the earth and our sphere, with which we revolve about the sun like any other planet. The earth has, then, more than one motion. • The apparent retrograde and direct motion of the planets arises not from their motion but from the earth's. The motion of the earth alone, therefore, suffices to explain so many apparent inequalities in the heavens.

12. 1543 De revolutionibus orbium coelestium(על הסיבובים של הגופים השמימיים) Commentariolus ~1514 (1878) • The center of the earth is not the center of the universe, but only of gravity and of the lunar sphere. Why did Copernicus decide to abandon geocentrism in favor of heliocentrism?

13. 1543 De revolutionibus orbium coelestium(על הסיבובים של הגופים השמימיים) Commentariolus ~1514 (1878) • The center of the earth is not the center of the universe, but only of gravity and of the lunar sphere. Why? Because geocentrism is wrong and heliocentrism is right!

14. De revolutionibus orbium coelestium For philosophical reasons, Copernicus clung to the belief that all the orbits of celestial bodies must be perfect circlesand to a belief in the unobserved crystalline spheres. This forced Copernicus to retain the Ptolemaic system's complex system of epicycles, to account for the observed deviations from circularity and to square his calculations with observations.

15. De revolutionibus orbium coelestium For philosophical reasons, … This forced Copernicus to retain … Despite Copernicus' adherence to these aspects of ancient astronomy, his radical shift from a geocentric to a heliocentric cosmology was a serious blow to Aristotle's science—and helped usher in the Scientific Revolution.

16. 1543 De revolutionibus orbium coelestium(על הסיבובים של הגופים השמימיים) Commentariolus ~1514 (1878) • The center of the earth is not the center of the universe, but only of gravity and of the lunar sphere. Why did Copernicus decide to abandon geocentrism in favor of heliocentrism? For most observable phenomena there is no real difference in the paths predicted by both systems! Video 15-17

17. 1543 De revolutionibus orbium coelestium(על הסיבובים של הגופים השמימיים) Commentariolus ~1514 (1878) • The center of the earth is not the center of the universe, but only of gravity and of the lunar sphere. Why did Copernicus decide to abandon geocentrism in favor of heliocentrism? What was the question for which heliocentrism was the answer?

18. 1543 De revolutionibus orbium coelestium(על הסיבובים של הגופים השמימיים) Commentariolus ~1514 (1878) What was the question for which heliocentrism was the answer? How did it happen that Copernicus’ ideas became gradually accepted and eventually led to a change in world-view?

19. 1543 De revolutionibus orbium coelestium(על הסיבובים של הגופים השמימיים) Commentariolus ~1514 (1878) What was the question for which heliocentrism was the answer? The Internalist Point of View

20. De revolutionibus orbium coelestium(על הסיבובים של הגופים השמימיים) 1543 Andreas Ossiander (1498-1552) Ad Lectorem It is the duty of an astronomer to compose the history of the celestial motions through careful and expert study. Then he must conceive and devise the causes of these motions or hypotheses about them. Since he cannot in any way attain to the true causes, he will adopt whatever suppositions enable the motions to be computed correctly ... The present author has performed both these duties excellently. For these hypotheses need not be true nor even probable. On the contrary, if they provide a calculus consistent with the observations, that alone is enough ...

21. De revolutionibus orbium coelestium(על הסיבובים של הגופים השמימיים) 1543 Andreas Ossiander (1498-1552) Ad Lectorem For this art, it is quite clear, is completely and absolutely ignorant of the causes of the apparent [movement of the heavens]. And if any causes are devised by the imagination, as indeed very many are, they are not put forward to convince anyone that they are true, but merely to provide a reliable basis for computation. However, since different hypotheses are sometimes offered for one and the same ... the astronomer will take as his first choice that hypothesis which is the easiest to grasp. The philosopher will perhaps rather seek the semblance of the truth. But neither of them will understand or state anything certain, unless it has been divinely revealed to him ... Let no one expect anything certain from astronomy, which cannot furnish it, lest he accept as the truth ideas conceived for another purpose, and depart this study a greater fool than when he entered.

22. De revolutionibus orbium coelestium(על הסיבובים של הגופים השמימיים) 1543 Preface and Dedication to Pope Paul III The only thing which induced me to look for another way of reckoning the movements of the heavenly bodies was that I knew that mathematicians by no means agree in their investigations thereof.

23. De revolutionibus orbium coelestium(על הסיבובים של הגופים השמימיים) 1543 For some employ concentric circles only; others, eccentric circles and epicycles; and even by these means they do not completely attain the desired end. For, although those who have depended upon concentric circles have shown that certain diverse motions can be deduced from these, yet they have not succeeded thereby in laying down any sure principle, corresponding indisputably to the phenomena. These, on the other hand, who have devised systems of eccentric circles, although they seem in great part to have solved the apparent movements by calculations which by these eccentrics are made to fit, have nevertheless introduced many things which seem to contradict the first principles of the uniformity of motion. [i.e. the equant!!]

24. De revolutionibus orbium coelestium(על הסיבובים של הגופים השמימיים) 1543 I began to grow disgusted that no more consistent scheme of the movements of the mechanism of the universe, set up for our benefit by that best and most law abiding Architect of all things, was agreed upon by philosophers who otherwise investigate so carefully the most minute details of this world. Wherefore I undertook the task of rereading the books of all the philosophers I could get access to, to see whether anyone ever was of the opinion that the motions of the celestial bodies were other than those postulated by the men who taught mathematics in the schools.

25. De revolutionibus orbium coelestium(על הסיבובים של הגופים השמימיים) 1543 I found first in Cicero that Nicetas thought that the Earth moved. And afterwards I found in Plutarch that there were some others of the same opinion: … “Some think that the Earth is at rest; but Philolaus the Pythagorean says that it moves around the fire with an obliquely circular motion, like the sun and moon. Herakleides of Pontus and Ekphantus the Pythagorean do not give the Earth any movement of locomotion, but rather a limited movement of rising and setting around its centre, like a wheel.”     …

26. 1543 De revolutionibus… Therefore I also, having found occasion, began to meditate upon the mobility of the Earth. And although the opinion seemed absurd, nevertheless because I knew that others before me had been granted the liberty of constructing whatever circles they pleased in order to demonstrate astral phenomena, I thought that I too would be readily permitted to test whether or not, by the laying down that the Earth had some movement, demonstrations less shaky than those of my predecessors could be found for the revolutions of the celestial spheres.

27. De revolutionibus orbium coelestium(על הסיבובים של הגופים השמימיים) 1543 I have found by many and long observations that if the movements of the other planets are assumed for the circular motion of the Earth and are substituted for the revolution of each star, not only do their phenomena follow logically therefrom, but the relative positions and magnitudes both of the stars and all their orbits, and of the heavens themselves, become so closely related that in none of its parts can anything be changed without causing confusion in the other parts and in the whole universe.

28. 1543 De revolutionibus orbium coelestium(על הסיבובים של הגופים השמימיים) • Book I • General vision of the heliocentric theory: • The universe is spherical. The celestial bodies, including the earth, are spherical and have regular circular and everlasting movements. The earth rotates on its axis and around the sun. • Why the ancients thought the earth was central? • The order of the planets around the sun and their periodicity. • Principles of spherical trigonometry and a table of chords.

29. 1543 De revolutionibus orbium coelestium(על הסיבובים של הגופים השמימיים) • Book II • Principles of spherical astronomy • A Detailed Catalogue of the Fixed Stars

30. 1543 De revolutionibus orbium coelestium(על הסיבובים של הגופים השמימיים) • Book III • “Precession of Equinoxes” and the apparent motion of the Sun “The Age of Aquarius”

31. Nicolaus Copernicus (1473-1543) 1543 De revolutionibusorbiumcoelestium Chapter 3: “How Earth Forms One Single Sphere with Water?” • Colón: “Earth and water together form one round body .” • “We should not heed certain Peripatetics who ... assert that that the earth emerges from water, because its weight is not equally distributed due to its cavities, its center of gravity being different from its center of magnitude.”

32. Nicolaus Copernicus (1473-1543) 1543 De revolutionibusorbiumcoelestium Chapter 3: “How Earth Forms One Single Sphere with Water?” • Colón: “Earth and water together form one round body .” • “This will be more clear when we add the islands discovered in our time under the kings of Spain and Portugal, and especially America, named after their finder, a ship’s captain. On account of its still undisclosed magnitude this is thought to be another inhabited world, and there are also many other islands, heretofore unknown. So we should wonder even less that the Antipodes exist.”

33. 1543 De revolutionibus orbium coelestium(על הסיבובים של הגופים השמימיים) Book IV - description of the orbital motion of the Moon. Book V - how to calculate the positions of the wandering stars in the heliocentric model (with tables for the five planets). Book VI - the digression in latitude from the ecliptic of the five planets.

34. Scientific Revolutions: Historical Perspective  What was the Scientific Revolution? The abandonment of an existing world view (Aristotelian-Scholastic) and the rise of a new one

35. Why did Copernicus decide to abandon geocentrism in favor of heliocentrism? Disadvantages of Heliocentrist Explanation: Center of the universe differs from center of gravity Earth motion is not felt Earth has three motions Opposes the scriptures The geocentric universe is much smaller – no parallax (Occam’s Razor)

36. Why did Copernicus decide to abandon geocentrism in favor of heliocentrism? Advantages of Heliocentrist Explanation: Retrograde motion of planets is explained with no need for epicycles Apparent Motion of the fixed stars receives a simple explanation – no need for motion of the big sphere of stars No need for an equant – motion of the stars is truly uniform (but on reality it is not!!)

37. Why did Copernicus decide to abandon geocentrism in favor of heliocentrism? Advantages of Heliocentrist Explanation: No need for an equant – motion of the stars is truly uniform (but on reality it is not!!) Yet the widespread [planetary theories], advanced by Ptolemy and most other [astronomers], although consistent with the numerical [data], seemed likewise to present no small difficulty. For these theories were not adequate unless they also conceived certain equalizing circles, which made the planet appear to move at all times with uniform velocity neither on its deferent sphere nor about its own [epicycle's] center. Hence this sort of notion seemed neither sufficiently absolute nor sufficiently pleasing to the mind. Therefore, having become aware of these [defects], I often considered whether there could perhaps be found a more reasonable arrangement of circles, from which every apparent irregularity would be derived while everything in itself would move uniformly, as is required by the rule of perfect motion. (Commentariolus)

38. Why did Copernicus decide to abandon geocentrism in favor of heliocentrism? Advantages of Heliocentrist Explanation: A greater harmony: “It is as though, in Ptolemy’s pictures, an artist were to bring together hands, feet, head, and other limbs from quite different models, each part being admirably drawn in itself, but without any common relation to a single body: since they would in no way match one another, the result would be a monster rather than a man.” (Commentarioulus)

39. Why did Copernicus decide to abandon geocentrism in favor of heliocentrism? Advantages of Heliocentrist Explanation: A necessary order of the planets: “the relative positions and magnitudes both of the stars and all their orbits, and of the heavens themselves, become so closely related that in none of its parts can anything be changed without causing confusion in the other parts and in the whole universe”.

40. Why did Copernicus decide to abandon geocentrism in favor of heliocentrism? Advantages of Heliocentrist Explanation: Simplicity?

41. Why did Copernicus decide to abandon geocentrism in favor of heliocentrism? Advantages of Heliocentrist Explanation: Simplicity?

43. Why did Copernicus decide to abandon geocentrism in favor of heliocentrism? What was the question for which heliocentrism was the answer?