Transcript moon size
ANCIENT ASTRONOMY Chapter 1 ANCIENT ASTRONOMY In the British Isles, stones were used to keep track of the Sun and Moon. Stonehenge ANCIENT ASTRONOMY The Chinese developed a working calendar and kept careful track of comets, eclipses sun spots and variable objects Early Chinese Star Chart ANCIENT ASTRONOMY The Mayan culture was able to accurately predict solar and lunar eclipses. The Mayans also developed a very accurate calendar, later adopted by the Aztecs. Dresden Codex This structure, called the Caracol, at Chitzen Itza may have been used as a Venus Observatory Aztec Calendar The Caracol EARLY GREEK ASTRONOMY Shape of Earth (circa 400 BC) LUNAR ECLIPSE GEOMETRY LIGHT RAYS FROM THE SUN LUNAR ECLIPSE Shape Earth: Erastothenes’ Method EARLY GREEK ASTRONOMY Shape of Earth (circa 400 BC) Size of Earth (Erastothenes circa 200 BC) 7/360 = AS/Circumference AS = (5000 Stadia) 800 km Circumference = 40,000 km Knowing p Radius = 6370 km FLASHCARD SUPPOSE THAT ERASTOTHENES HAD MEASURED THAT THE SUN WAS OVERHEAD AT SYENE AND 9 DEGREES AWAY FROM OVERHEAD AT ALEXANDRIA. WHAT WOULD HE HAVE CONCLUDED FOR THE RADIUS OF EARTH IF THE SYENE-ALEXANDRIA DISTANCE WAS 1200 KM? A) 7639 km B) 15,278 km C) 24,000 km D) 48,000 km EARLY GREEK ASTRONOMY Shape of Earth (circa 400 BC) Size of Earth (Erastothenes circa 200 BC) Relative Size of Earth and the Moon (Aristarchus circa 280 BC) From lunar eclipse ~1/3 LIGHT RAYS from the SUN LUNAR ECLIPSE EARLY GREEK ASTRONOMY Shape of Earth (circa 400 BC) Size of Earth (Erastothenes circa 200 BC) Relative Size of Earth and the Moon (Aristarchus circa 280 BC) Size of the Moon, Distance to the Moon Radius = 1730 km (0.27 Earth) Distance = 380,000 km – from size and angular size EARLY GREEK ASTRONOMY Shape of Earth (circa 400 BC) Size of Earth (Erastothenes circa 200 BC) Relative Size of Earth and the Moon (Aristarchus circa 280 BC) Size of the Moon, Distance to the Moon Distance to the Sun EARLY GREEK ASTRONOMY Angular size Sun, Moon did not change (circular) cos X = Dmoon/Dsun Dmoon already known – measure X - failed X close to 90o – if 90 Sun infinitely far away Modern X = 89o 51’ Sun 380 times farther than Moon X HELIOCENTRIC SOLAR SYSTEM Greek Argument that the Sun is at the Centre of the Solar System Sun is much farther from Earth than the Moon (380 times farther) Since the Sun and Moon have the same angular size, Sun is 380 times larger than Moon Earth is 3 times larger than the Moon, thus the Sun is 100 times larger than Earth Thus, the Sun is much more massive than Earth (assumes both have about the same density) Hence, the Greeks concluded the the Sun is at the centre of the system (circa 200 BC)