the origin of modern astronomy chapter 4. the preceding chapters gave you a modern view of earth....
TRANSCRIPT
![Page 1: The Origin of Modern Astronomy Chapter 4. The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun](https://reader035.vdocument.in/reader035/viewer/2022081503/5697c0141a28abf838ccd015/html5/thumbnails/1.jpg)
The Origin of Modern Astronomy
Chapter 4
![Page 2: The Origin of Modern Astronomy Chapter 4. The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun](https://reader035.vdocument.in/reader035/viewer/2022081503/5697c0141a28abf838ccd015/html5/thumbnails/2.jpg)
The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun move through space and how that produces the sights you see in the sky. But how did humanity first realize that we live on a planet moving through space?
That required revolutionary overthrow of an ancient and honored theory of Earth’s place. By the 16th century, many astronomers were uncomfortable with the ancient theory that Earth sat at the center of a spherical universe. In this chapter, you will discover how a Polish astronomer named Nicolaus Copernicus changed the old theory, how a German astronomer named Johannes Kepler discovered the laws of planetary motion, and how the Italian Galileo Galilei changed what we know about nature.
Guidepost
![Page 3: The Origin of Modern Astronomy Chapter 4. The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun](https://reader035.vdocument.in/reader035/viewer/2022081503/5697c0141a28abf838ccd015/html5/thumbnails/3.jpg)
Here you will find answers to four essential questions:
• How did classical philosophers describe Earth’s place in the Universe?
• How did Copernicus revise that ancient theory?
• How did astronomers discover the laws of planetary motion?
• Why was Galileo condemned by the Inquisition?
Guidepost (continued)
This chapter is not just about the history of astronomy. As they struggled to understand Earth and the heavens, the astronomers of the Renaissance invented a new way of understanding nature – a way of thinking that is now called science.
![Page 4: The Origin of Modern Astronomy Chapter 4. The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun](https://reader035.vdocument.in/reader035/viewer/2022081503/5697c0141a28abf838ccd015/html5/thumbnails/4.jpg)
I. The Roots of AstronomyA. ArchaeoastronomyB. The Astronomy of GreeceC. Aristotle and the Nature of EarthD. The Ptolemaic Universe
II. The Copernican RevolutionA. The Copernican ModelB. De Revolutionibus
III. Planetary MotionA. Tycho BraheB. Tycho Brahe's LegacyC. Kepler: An Astronomer of Humble OriginsD. Joining TychoE. Kepler's Three Laws of Planetary MotionE. The Rudolphine Tables
Outline
![Page 5: The Origin of Modern Astronomy Chapter 4. The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun](https://reader035.vdocument.in/reader035/viewer/2022081503/5697c0141a28abf838ccd015/html5/thumbnails/5.jpg)
IV. Galileo GalileiA. Telescopic ObservationsB. Dialogo and Trial
V. Modern Astronomy
Outline (contd.)
![Page 6: The Origin of Modern Astronomy Chapter 4. The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun](https://reader035.vdocument.in/reader035/viewer/2022081503/5697c0141a28abf838ccd015/html5/thumbnails/6.jpg)
The Roots of Astronomy• Already in the stone and bronze ages, human
cultures realized the cyclic nature of motions in the sky.
• Monuments dating back to ~ 3000 B.C. show alignments with astronomical significance.
• Those monuments were probably used as
calendars or even to predict eclipses.
Newgrange, Ireland, built around 3200 B.C.:
Sunlight shining down a passageway into the central chamber of the mount indicates the day of winter solstice.
![Page 7: The Origin of Modern Astronomy Chapter 4. The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun](https://reader035.vdocument.in/reader035/viewer/2022081503/5697c0141a28abf838ccd015/html5/thumbnails/7.jpg)
Stonehenge
• Alignments with locations of sunset, sunrise, moonset and moonrise at summer and winter solstices
Summer solstice
Heelstone
• Constructed: 3000 – 1800 B.C.
• Probably used as calendar
![Page 8: The Origin of Modern Astronomy Chapter 4. The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun](https://reader035.vdocument.in/reader035/viewer/2022081503/5697c0141a28abf838ccd015/html5/thumbnails/8.jpg)
Other Examples All Around the World
Chaco Canyon, New Mexico
Slit in the rock formation produces a sunlit “dagger” shape,
indicating the day of summer solstice
![Page 9: The Origin of Modern Astronomy Chapter 4. The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun](https://reader035.vdocument.in/reader035/viewer/2022081503/5697c0141a28abf838ccd015/html5/thumbnails/9.jpg)
Other Examples All Around the World (2)
Mammoth tusk found at Gontzi, Ukraine: Inscriptions probably describing
astronomical events
![Page 10: The Origin of Modern Astronomy Chapter 4. The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun](https://reader035.vdocument.in/reader035/viewer/2022081503/5697c0141a28abf838ccd015/html5/thumbnails/10.jpg)
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.
![Page 11: The Origin of Modern Astronomy Chapter 4. The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun](https://reader035.vdocument.in/reader035/viewer/2022081503/5697c0141a28abf838ccd015/html5/thumbnails/11.jpg)
Ancient Greek Astronomers (2)Models were generally wrong because they were based on wrong “first principles”, believed to be
“obvious” and not questioned:
1. Geocentric Universe: Earth at the Center of the Universe
2. “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.
![Page 12: The Origin of Modern Astronomy Chapter 4. The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun](https://reader035.vdocument.in/reader035/viewer/2022081503/5697c0141a28abf838ccd015/html5/thumbnails/12.jpg)
Ancient Greek Astronomers (3)• Eudoxus (409 – 356 B.C.):
Model of 27 nested spheres
1. Imperfect, changeable Earth,
• He expanded Eudoxus’ Model to use 55 spheres.
2. Perfect Heavens (described by spheres)
• Aristotle (384 – 322 B.C.), major authority of philosophy until the late middle ages:
Universe can be divided in 2 parts:
![Page 13: The Origin of Modern Astronomy Chapter 4. The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun](https://reader035.vdocument.in/reader035/viewer/2022081503/5697c0141a28abf838ccd015/html5/thumbnails/13.jpg)
Eratosthenes (~ 200 B.C.):Calculation of the Earth’s radius
Angular distance between Syene and Alexandria:
~ 70
Linear distance between Syene and Alexandria:
~ 5,000 stadia
Earth Radius ~ 40,000 stadia (probably ~ 14 % too large) – better than
any previous radius estimate
![Page 14: The Origin of Modern Astronomy Chapter 4. The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun](https://reader035.vdocument.in/reader035/viewer/2022081503/5697c0141a28abf838ccd015/html5/thumbnails/14.jpg)
Later refinements (2nd century B.C.) • Hipparchus: Placing the Earth away from the centers of the
“perfect spheres”
• Ptolemy: Further refinements, including epicycles
![Page 15: The Origin of Modern Astronomy Chapter 4. The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun](https://reader035.vdocument.in/reader035/viewer/2022081503/5697c0141a28abf838ccd015/html5/thumbnails/15.jpg)
Epicycles
The Ptolemaic model was considered the “standard model” of the Universe until the
Copernican Revolution.
Introduced to explain retrograde (westward)
motion of planets
![Page 16: The Origin of Modern Astronomy Chapter 4. The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun](https://reader035.vdocument.in/reader035/viewer/2022081503/5697c0141a28abf838ccd015/html5/thumbnails/16.jpg)
The Copernican Revolution
Nicolaus Copernicus (1473 – 1543):
Heliocentric Universe (Sun in the Center)
![Page 17: The Origin of Modern Astronomy Chapter 4. The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun](https://reader035.vdocument.in/reader035/viewer/2022081503/5697c0141a28abf838ccd015/html5/thumbnails/17.jpg)
Copernicus’ New (and Correct) Explanation for the Retrograde Motion of the Planets
This made Ptolemy’s epicycles unnecessary.
Retrograde (westward) motion of a planet occurs when the Earth passes the planet.
![Page 18: The Origin of Modern Astronomy Chapter 4. The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun](https://reader035.vdocument.in/reader035/viewer/2022081503/5697c0141a28abf838ccd015/html5/thumbnails/18.jpg)
Tycho Brahe (1546 – 1601)• High precision observations of the
positions of stars and planets
• Evidence against Aristotelian belief of
“perfect”, unchangeable
heavens
• Measurement of the nightly
motion of a “new star” (supernova)
showed no parallax
![Page 19: The Origin of Modern Astronomy Chapter 4. The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun](https://reader035.vdocument.in/reader035/viewer/2022081503/5697c0141a28abf838ccd015/html5/thumbnails/19.jpg)
Tycho Brahe’s Legacy
New World model
• Sun and Moon orbit Earth;
Planets orbit the sun.
• Still geocentric (Earth in the center of the sphere of stars)
![Page 20: The Origin of Modern Astronomy Chapter 4. The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun](https://reader035.vdocument.in/reader035/viewer/2022081503/5697c0141a28abf838ccd015/html5/thumbnails/20.jpg)
Johannes Kepler (1571 – 1630)
• Used the precise observational tables of Tycho Brahe to study
planetary motion mathematically.
1. Circular motion
• Planets move around the sun on elliptical paths, with non-uniform velocities.
• Found a consistent description by
abandoning both
2. Uniform motion
![Page 21: The Origin of Modern Astronomy Chapter 4. The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun](https://reader035.vdocument.in/reader035/viewer/2022081503/5697c0141a28abf838ccd015/html5/thumbnails/21.jpg)
Kepler’s Laws of Planetary Motion
1.The orbits of the planets are ellipses with the sun at one focus.
Eccentricity e = c/a
c
![Page 22: The Origin of Modern Astronomy Chapter 4. The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun](https://reader035.vdocument.in/reader035/viewer/2022081503/5697c0141a28abf838ccd015/html5/thumbnails/22.jpg)
Eccentricities of Ellipses
e = 0.02 e = 0.1 e = 0.2
e = 0.4 e = 0.6
1) 2) 3)
4) 5)
![Page 23: The Origin of Modern Astronomy Chapter 4. The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun](https://reader035.vdocument.in/reader035/viewer/2022081503/5697c0141a28abf838ccd015/html5/thumbnails/23.jpg)
Eccentricities of Planetary OrbitsOrbits of planets are virtually
indistinguishable from circles:
Earth: e = 0.0167Most extreme example:
Pluto: e = 0.248
![Page 24: The Origin of Modern Astronomy Chapter 4. The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun](https://reader035.vdocument.in/reader035/viewer/2022081503/5697c0141a28abf838ccd015/html5/thumbnails/24.jpg)
Planetary Orbits (2)
2. A line from a planet to the sun sweeps over equal areas in equal intervals of time.
![Page 25: The Origin of Modern Astronomy Chapter 4. The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun](https://reader035.vdocument.in/reader035/viewer/2022081503/5697c0141a28abf838ccd015/html5/thumbnails/25.jpg)
Planetary Orbits (3)
3. A planet’s orbital period (P) squared is proportional to its average distance from the sun (a) cubed:
Py2 = aAU
3(Py = period in years; aAU = distance in AU)
![Page 26: The Origin of Modern Astronomy Chapter 4. The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun](https://reader035.vdocument.in/reader035/viewer/2022081503/5697c0141a28abf838ccd015/html5/thumbnails/26.jpg)
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
![Page 27: The Origin of Modern Astronomy Chapter 4. The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun](https://reader035.vdocument.in/reader035/viewer/2022081503/5697c0141a28abf838ccd015/html5/thumbnails/27.jpg)
Major Discoveries of Galileo• Moons of Jupiter (4 Galilean moons)
• Rings of Saturn
(What he really saw)
![Page 28: The Origin of Modern Astronomy Chapter 4. The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun](https://reader035.vdocument.in/reader035/viewer/2022081503/5697c0141a28abf838ccd015/html5/thumbnails/28.jpg)
Major Discoveries of Galileo (2)• Surface structures on the moon; first estimates
of the height of mountains on the moon
![Page 29: The Origin of Modern Astronomy Chapter 4. The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun](https://reader035.vdocument.in/reader035/viewer/2022081503/5697c0141a28abf838ccd015/html5/thumbnails/29.jpg)
Major Discoveries of Galileo (3)
• Sun spots (proving that the sun is not perfect!)
![Page 30: The Origin of Modern Astronomy Chapter 4. The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun](https://reader035.vdocument.in/reader035/viewer/2022081503/5697c0141a28abf838ccd015/html5/thumbnails/30.jpg)
Major Discoveries of Galileo (4)• Phases of Venus (including “full Venus”),
proving that Venus orbits the sun, not the Earth!
![Page 31: The Origin of Modern Astronomy Chapter 4. The preceding chapters gave you a modern view of Earth. You can now imagine how Earth, the moon, and the sun](https://reader035.vdocument.in/reader035/viewer/2022081503/5697c0141a28abf838ccd015/html5/thumbnails/31.jpg)
Historical Overview