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Earth Science 104

Earth’s Place in the Cosmos, StructureHistory of Astronomy

Introduction

• No lab this week– Must pass lab to

pass this class– Instructors will

give percent lab grade to one another

• Get Lab Manual this week– Do PRELAB 1

before lab next week

– Bring manual to lab each week

Peer Led Instruction

• Library—Wednesday 6:30 to 8:30 PM• Kristin Mooney—Science Education Major• Add ES104X—CRN 11017

• First Session: Sept 26, 2007– Do review questions to see if you think it help– Sit in to see if it is for you– Can add before Oct. 3 session

Scales of

Space and Time

Planet EarthSphere

interactions

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Atmosphere Biospherehttp://www.earthscienceeducation.com/creative_science/chemistry_index.htm

Geosphere

http://www.miamisci.org/ecolinks/geosphere.html

Tectonic Plates

Crust

http://earthquake.usgs.gov/learning/glossary.php?term=crust

Tectonic movements

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Complex Interactions

http://www.msu.edu/~colungag/docs/philosophy.htm

Hydrologic Cycle

http://www.mnforsustain.org/water_climate_global_water_cycle_study.htm

Internal and external cycles Convection

Earth’s Structure• Rocky Planet

– Silicates– Metals

• Melting allowed gravity to separate by density– Metals drawn to center– Silicates dominate the remainder

• Oxygen and Silicon most common elements• Combine with other elements to make feldspars,

pyroxenes, amphiboles and quartz

Composition

• Core ~ 3500 km radius

• Mantle ~ 2900 km thick

• Crust < 100 km

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Earth’s Interior

Properties

• Inner core• Outer core• Lower mantle• Asthenosphere• Lithosphere

In Class Activity 1

a. What similarities exist in the classification of Earth’s interior based on composition and on properties?

b. Identify differences in the classification of Earth’s interior by composition or by physical properties

Internal Division

• Mantle-Crust boundary is compositional– More silica, less iron, magnesium in crust

• Asthenosphere-Lithosphere boundary is based on properties– Asthenosphere is weak, flows– Lithosphere is rigid

Interface of spheres

Nebular Hypothesis of Solar System Formation.

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Nebular Hypothesis

• NEBULA– Rotating cloud of dust and gases – Collapses into solid bodies

• Formed our solar system– Sun– Major Planets– Dwarf planets, asteroids and comets

Solar system formed

from nebular cloud

Big Bang forms all matter

• Much more ancient than nebular collapse• “Beginning of the universe”

In Class Activity 2

a. What is a nebula?b. Was the ‘big bang’ the event that formed

our solar system?

History of Astronomy

• Ancient civilizations believed that Earth was at the center of the universe—GEOCENTRIC MODEL

• Age of Reason beginning to recognize Sun is center of Solar System—HELIOCENTRIC MODEL

• Age of Technology exploring wide reaches of the universe

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Anaxagoras• 5th century B.C.• Moon is a sphere

lighted by Sun

http://www-history.mcs.st-andrews.ac.uk/Biographies/Anaxagoras.html

Aristotle

• 4th century BC• Earth is a sphere

http://www.hao.ucar.edu/public/education/sp/images/aristotle.html

Eratosthenes calculatedEarth’s size in ~ 240 BC

http://en.wikipedia.org/wiki/Eratosthenes#Measurement_of_the_Earth

Ptolemy’s map of Europe

http://archive.ncsa.uiuc.edu/SDG/Experimental/vatican.exhibit/exhibit/full-images/d-mathematics/math21.gif

Retrograde motion

• Mars usually moves across sky west to east• Occasionally appears to move east to west• Occurs when Earth is ‘passing’ Mars

Ptolemy’s Solar System

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Epicycle explains retrograde motion

• Since thought was Earth is the center

Ptolemy’s work

• Amalgest compiled in 141 BC• Survived by preservation in libraries in Persia• Rediscovered by Europeans as Arabic

translations of the original Greek• Translated into Latin in 13th century• Influenced intellectual thought for centuries

NicolausCopernicus

• Earth rotates on an axis, instead of everything orbiting Earth

• Earth orbits Sun like the planets, so it a planet too

• “On the Revolution of the Heavenly Spheres”, 1543

http://www.hao.ucar.edu/public/education/sp/images/copernicus.html

Arguments against Heliocentric Model

• Earth would fly apart if it rotated on an axis• Moon would be left behind if Earth orbited

Sun• Since God created Earth and Sun and all

the heavenly bodies, Earth is the center of the universe

In Class Activity 3Come up with examples or evidence to

counter these argumentsa. Earth would fly apart if it rotated on an

axisb. Moon would be left behind if Earth

orbited Sun

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Tycho Brahe

• Detailed observations of movement of planets

http://www.hao.ucar.edu/public/education/sp/images/tycho.html

Tycho Brahe in his observatory

• His careful observations and records are his most important legacy

http://www.hao.ucar.edu/public/education/sp/images/tycho.3.html

Tycho’s 1572 Nova

observations

http://www.hao.ucar.edu/public/education/sp/images/tycho.1.html

Tycho’s comet of 1577

http://www.hao.ucar.edu/public/education/sp/images/tycho.2.html

Tycho’smodel of

solar system• Discounted

Copernicus model because he could not discern stellar parallax

• It does exist, he didn’t have tools to see it

http://www.hao.ucar.edu/public/education/sp/images/tycho.4.html

Johannes Kepler

• Tycho’s assistant and successor

• Used Tycho’s data to determine planetary orbits are elliptical

http://en.wikipedia.org/wiki/Image:Johannes_Kepler.jpg

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First Law of Planetary Motion

• Orbit of planet is ellipse

• Sun at one Focus

Kepler’s 2nd Law

• Equal areas in equal time intervals accounts for the uneven speeds

Kepler’s third law of planetary motion

• p2=d3

p=Period (time to orbit Sun) in Earth yearsd=Distance in Astronomical Units:

1 A.U.=distance from Earth to Sun

Galileo Galilei• Strong supporter of

Copernican model of planetary movement

• Built 30x telescopes and looked at planets and Moon starting in 1609

http://en.wikipedia.org/wiki/Galileo_Galilei#Technology

Galileo’s Astronomical Discoveries

• Planets look like discs, not points of light• Jupiter has moons• Venus has phases• Moon’s surface has texture• Sun rotates on an axis

Galileo’s notes on Jupiter’s moons

• Telescope used to see that another body in solar system is a center of orbital movement

• These moons are not left behind, and Earth’s Moon is not either

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Ptolemaic version of Venus Phases of Venus

Galileo’s explanation of Venus’phases Moon’s surface has texture

Isaac Newton

• Invented the calculus to simplify calculations

• Explained the orbital motion of planets as the interaction of inertia and gravity

Orbital motion of planets