origin of modern astronomy chapter 22. 22.1 early astronomy a.ancient greeks aristotle- earth is...
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Origin of Modern Astronomy
Chapter 22
22.1 Early Astronomy
A. Ancient GreeksAristotle- Earth is round because it casts a curved shadow on the Moon. (Luna eclipse)
22.1 Early Astronomy
A. Ancient GreeksEratosthenes- measured the earth’s diameter.
22.1 Early AstronomyA. Ancient Greeks
Hipparchus (2nd century B.C.)Star chart of 850 stars
22.1 Early AstronomyA. Ancient GreeksGeocentric Model- earth centered and all
objects “orbit” about the earth.Heliocentric Model- Sun centered
22.1 Early AstronomyA. Ancient GreeksPtolemaic System-PtolemyNeeded “epicycles” to makeplanets “retrograde”
22.1 Early AstronomyB. Birth of Modern AstronomyNicolaus Copernicus (1473-1543)Supported the Heliocentric Model in opposition
of the Church.
22.1 Early AstronomyB. Birth of Modern AstronomyTycho Brahe (1546-1601)Very precise positions of Mars
Johannes Kepler (1571-1630)Used Brahe’s information to discover3 planetary laws.
22.1 Early AstronomyB. Birth of Modern AstronomyKepler’s Planetary Motion Laws1. Move in ellipses. 2. Sweep out equal sectors in equal time.3. Distance from Sun determines period of orbit.
22.1 Early AstronomyB. Birth of Modern AstronomyGalileo Galilei (1564-1642) Pointed at telescope
toward the stars…..1. 4 satellites about Jupiter2. Planets were discs not pinpoints3. Venus had “phases”4. The Moon was not smooth5. The Sun had “spots”
22.1 Early AstronomyB. Birth of Modern AstronomySir Isaac Newton (1642-1727)Described laws of motion. First-
inertia.Formulated and tested the
Universal Law of GravitationGravity directly proportional to
mass and inversely proportional to square of distance
22.2 Earth-Moon-Sun SystemA. Motions of EarthRotation-spin (1 day)Revolution-moves around Sun (1 yr.)Precession-swing about the axis (26 000 yr.)
22.2 Earth-Moon-Sun SystemA. Motions of EarthRotationSolar Day-time Sun returns to same
position. About 24 hoursSidereal Day- turn 360o, 23h 56m 4s
22.2 Earth-Moon-Sun SystemA. Motions of EarthRevolution
Perihelion- 150 million kmAphelion- 152 million km
22.2 Earth-Moon-Sun SystemA. Motions of EarthRevolution
Seasons because of axis tilt
22.2 Earth-Moon-Sun SystemA. Motions of EarthPrecession26 000 years
Change of tilt21.5o to 24.5o
41 000 years
22.2 Earth-Moon-Sun SystemA. Motions of EarthSolar System moving toward Vega at
20 km/s.
Revolve aboutthe Milky Wayat 250 km/s230 million year
22.2 Earth-Moon-Sun SystemB. Earth-Moon SystemPerigee-closestApogee-farthest
22.2 Earth-Moon-Sun SystemB. Earth-Moon SystemPhases of the Moon
22.2 Earth-Moon-Sun SystemB. Earth-Moon SystemSynodic month- 29 ½ days
(Roman calendar)Sidereal month-27 1/3 days2 more days to make a New Moon Revolves at 27 1/3days. (same side)
22.2 Earth-Moon-Sun SystemB. Earth-Moon
SystemEclipses
Full Moon-LunaNew Moon- Solar
http://eclipse.gsfc.nasa.gov/eclipse.html
22.3 Earth’s MoonFacts:3475 km diameter3.3x dense as water1/6 G or 150 lbs man=
25 lbs on Moon
A. Lunar Surface: dark lowlands
bright highlands
22.3 Earth’s MoonA. Lunar Surface: Craters- impacts by
space debris
22.3 Earth’s MoonA. Lunar Surface: Craters- Bright rays
are created by recent impacts.
22.3 Earth’s MoonA. Lunar Surface: Highlands:Some mountains are 8
km high.
22.3 Earth’s MoonA. Lunar Surface: Maria: basaltic lava
that “bleed out”Rilles- lava flows
22.3 Earth’s MoonA. Lunar Surface: Regolith: ignous
rock , beads and dust.
22.3 Earth’s MoonA. Lunar History Most accepted
model is Mars sized body collided with Earth.