Origin of Modern Astronomy Chapter 22
22.1 Early Astronomy A.Ancient Greeks Aristotle- Earth is round because it casts a curved shadow on the Moon. (Luna eclipse)
22.1 Early Astronomy A.Ancient Greeks Eratosthenes- measured the earth’s diameter.
22.1 Early Astronomy A.Ancient Greeks Hipparchus (2 nd century B.C.) Star chart of 850 stars
22.1 Early Astronomy A.Ancient Greeks Geocentric Model- earth centered and all objects “orbit” about the earth. Heliocentric Model- Sun centered
22.1 Early Astronomy A.Ancient Greeks Ptolemaic System-Ptolemy Needed “epicycles” to make planets “retrograde”
22.1 Early Astronomy B.Birth of Modern Astronomy Nicolaus Copernicus ( ) Supported the Heliocentric Model in opposition of the Church.
22.1 Early Astronomy B.Birth of Modern Astronomy Tycho Brahe ( ) Very precise positions of Mars Johannes Kepler ( ) Used Brahe’s information to discover 3 planetary laws.
22.1 Early Astronomy B.Birth of Modern Astronomy Kepler’s Planetary Motion Laws 1.Move in ellipses. 2.Sweep out equal sectors in equal time. 3.Distance from Sun determines period of orbit.
22.1 Early Astronomy B.Birth of Modern Astronomy Galileo Galilei ( ) Pointed at telescope toward the stars… satellites about Jupiter 2.Planets were discs not pinpoints 3.Venus had “phases” 4.The Moon was not smooth 5.The Sun had “spots”
22.1 Early Astronomy B.Birth of Modern Astronomy Sir Isaac Newton ( ) Described laws of motion. First- inertia. Formulated and tested the Universal Law of Gravitation Gravity directly proportional to mass and inversely proportional to square of distance
22.2 Earth-Moon-Sun System A. Motions of Earth Rotation-spin (1 day) Revolution-moves around Sun (1 yr.) Precession-swing about the axis ( yr.)
22.2 Earth-Moon-Sun System A. Motions of Earth Rotation Solar Day-time Sun returns to same position. About 24 hours Sidereal Day- turn 360 o, 23h 56m 4s
22.2 Earth-Moon-Sun System A. Motions of Earth Revolution Perihelion- 150 million km Aphelion- 152 million km
22.2 Earth-Moon-Sun System A. Motions of Earth Revolution Seasons because of axis tilt
22.2 Earth-Moon-Sun System A. Motions of Earth Precession years Change of tilt 21.5 o to 24.5 o years
22.2 Earth-Moon-Sun System A.Motions of Earth Solar System moving toward Vega at 20 km/s. Revolve about the Milky Way at 250 km/s 230 million year
22.2 Earth-Moon-Sun System B. Earth-Moon System Perigee-closest Apogee-farthest
22.2 Earth-Moon-Sun System B. Earth-Moon System Phases of the Moon
22.2 Earth-Moon-Sun System B. Earth-Moon System Synodic month- 29 ½ days (Roman calendar) Sidereal month-27 1/3 days 2 more days to make a New Moon Revolves at 27 1/3 days. (same side)
22.2 Earth-Moon-Sun System B.Earth-Moon System Eclipses Full Moon-Luna New Moon- Solar
22.3 Earth’s Moon Facts: 3475 km diameter 3.3x dense as water 1/6 G or 150 lbs man= 25 lbs on Moon A.Lunar Surface: dark lowlands bright highlands
22.3 Earth’s Moon A.Lunar Surface: Craters- impacts by space debris
22.3 Earth’s Moon A.Lunar Surface: Craters- Bright rays are created by recent impacts.
22.3 Earth’s Moon A.Lunar Surface: Highlands: Some mountains are 8 km high.
22.3 Earth’s Moon A.Lunar Surface: Maria: basaltic lava that “bleed out” Rilles- lava flows
22.3 Earth’s Moon A.Lunar Surface: Regolith: ignous rock, beads and dust.
22.3 Earth’s Moon A.Lunar History Most accepted model is Mars sized body collided with Earth.