All that is required to measure the diameter of the Earth is a person with stick and a brain. -adapted from Big Bang, Simon Singh, p.13 1
Announcements: Quiz #2: Monday, September 26 at beginning of class. Will cover Chp. 1-3. Quiz will last 15-30 minutes and will be followed by lecture. 2
Chapter 4 The Origin of Modern Astronomy
Several important people are introduced in Chapter 4. Name three of them and tell me about their contribution to our knowledge of the Solar System. 4
Outline I. The Roots of Astronomy A. Archaeoastronomy B. The Astronomy of Greece C. Aristotle and the Nature of Earth D. The Ptolemaic Universe II. The Copernican Revolution A. Copernicus the Revolutionary B. De Revolutionibus C. Galileo the Defender D. The Trial of Galileo III. 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 E. The Rudolphine Tables IV. Modern Astronomy
The Roots of Astronomy
The Roots of Astronomy Monuments dating back to ~ 3000 B.C. show alignments with astronomical significance. 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.
Stonehenge
Stonehenge
Stonehenge Constructed: 3000 1800 B.C.
Stonehenge Constructed: 3000 1800 B.C. Alignments with locations of sunset, sunrise, moonset and moonrise at summer and winter solstices
Stonehenge Constructed: 3000 1800 B.C. Alignments with locations of sunset, sunrise, moonset and moonrise at summer and winter solstices Probably used as calendar
Stonehenge Summer solstice Constructed: 3000 1800 B.C. Alignments with locations of sunset, sunrise, moonset and moonrise at summer and winter solstices Probably used as calendar
Stonehenge Summer solstice Heelstone Constructed: 3000 1800 B.C. Alignments with locations of sunset, sunrise, moonset and moonrise at summer and winter solstices Probably used as calendar
Other Examples All Around the World Chaco Canyon, New Mexico
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
Other Examples All Around the World (2) Mammoth tusk found at Gontzi, Ukraine: Inscriptions probably describing astronomical events
Ancient Greek Astronomers - Earth s shape - Earth s size - Earth s position - Scale of the Solar System
Ancient Greek Astronomers Ancient Greek s tried to explain the Universe using mathematical models. - Earth s shape - Earth s size - Earth s position - Scale of the Solar System
Ancient Greek Astronomers You ve just met a member of The Flat Earth Society who believes all NASA images are fake. You want to provide evidence that the Earth is spherical. What might you say/do? 11
Ancient Greek Astronomers You ve just met a member of The Flat Earth Society who believes all NASA images are fake. You want to provide evidence that the Earth is spherical. What might you say/do? 1. Watch a ship sail away. 2. Make a long-distance phone call and compare relative position of Sun and/or stars. 3. Observe a lunar eclipse.and look at the stars. 11
Ancient Greek Astronomers Earth s shadow is round as seen during an 12 eclipse
Scale of the Solar System 13
Eratosthenes (~ 200 B.C.): Calculation of the Earth s radius Second largest city of Egypt; main port Aswan Dam, Egypt 14
Eratosthenes (~ 200 B.C.): Calculation of the Earth s radius Sun at noon on summer solstice in Syene is straight overhead. Sun at noon on summer solstice in Alexandria is 7 degrees off the zenith. 15
Eratosthenes (~ 200 B.C.): Calculation of the Earth s radius 7 7 16
Eratosthenes (~ 200 B.C.): Calculation of the Earth s radius 7 7 16
Eratosthenes (~ 200 B.C.): Calculation of the Earth s radius Suppose you were an alien living on the fictitious warlike planet Myrmidon and you wanted to measure its size. The planet s sun is shining directly down a missile silo 1000 miles to your south, while at your location, it is 36 degrees from straight overhead. What is the circumference of Myrmidon? a. 36,000 mi b. 3,600 mi c. 10,000 mi d. 6,280 mi e. 1,590 mi 17
Scale of the Solar System Size of the Earth + Lunar Eclipse Observations Size of Moon!!! 18
Scale of the Solar System Size of the Moon + Angular Size in Sky Distance to Moon!!! 19
Scale of the Solar System Distance to the Moon + Sun/Moon Angle Distance to Sun!!! 20
Scale of the Solar System Distance to the Sun + Angular Size in Sky Distance to Sun!!! 21
Structure of the Solar System 22
Geocentric Models 23
Geocentric Models Eudoxus (409 356 B.C.): Model of 27 nested spheres 23
Geocentric Models Eudoxus (409 356 B.C.): Model of 27 nested spheres 23
Geocentric Models Eudoxus (409 356 B.C.): Model of 27 nested spheres Aristotle (384 322 B.C.), major authority of philosophy until the late middle ages: Universe can be divided in 2 parts: 23
Geocentric Models Eudoxus (409 356 B.C.): Model of 27 nested spheres Aristotle (384 322 B.C.), major authority of philosophy until the late middle ages: Universe can be divided in 2 parts: 1. Imperfect, changeable Earth, 23
Geocentric Models Eudoxus (409 356 B.C.): Model of 27 nested spheres Aristotle (384 322 B.C.), major authority of philosophy until the late middle ages: Universe can be divided in 2 parts: 1. Imperfect, changeable Earth, 2. Perfect Heavens (described by spheres) 23
The Wanderers Planet: from Greek πλανήτης αστήρ planētēs astēr "wandering star" 24
The Wanderers Planet: from Greek πλανήτης αστήρ planētēs astēr "wandering star" Motion of the planets across the sky is markedly different than the motion of the stars. Retrograde (westward) motion of a planet occurs when the Earth passes the planet. 24
Refinements to Geocentric Models Ptolemy s epicycles (150 AD) Publication: Syntaxis (the greatest) Model survived until Copernican Revolution of 1500 s. 25