Handout 27-2Handout 27-2

Models of the Solar SystemModels of the Solar System

11

The first astronomers thought that the stars, The first astronomers thought that the stars, planets, and sun revolved aroundplanets, and sun revolved around

C.C. Earth Earth

EARLY MODELS OF THE EARLY MODELS OF THE SOLAR SYSTEMSOLAR SYSTEM

22More than 2,000 years ago, the Greek More than 2,000 years ago, the Greek

philosopher Aristotle suggested a model of philosopher Aristotle suggested a model of the solar system that was Earth-centered, the solar system that was Earth-centered, ororA.A. geocentric geocentric

33The pattern by which planets appear to The pattern by which planets appear to

move backward in the sky relative to the move backward in the sky relative to the stars is called stars is called C.C. retrograde motion retrograde motion

44The Greek astronomer Claudius Ptolemy The Greek astronomer Claudius Ptolemy

proposed that planets moved in small proposed that planets moved in small circles, or epicycles, as they circles, or epicycles, as they D.D. revolved in larger circles around Earth. revolved in larger circles around Earth.

Ptolemy’s Model - GeocentricPtolemy’s Model - Geocentric

Ptolemey’s Design and explanationPtolemey’s Design and explanation

55The Polish astronomer Nicolaus The Polish astronomer Nicolaus

Copernicus proposed a model of the solar Copernicus proposed a model of the solar system that was sun-centered, orsystem that was sun-centered, orC.C. heliocentric heliocentric

66According to Copernicus, all the planets According to Copernicus, all the planets

revolved aroundrevolved arounda. a. the sun in the same direction but at different the sun in the same direction but at different

speeds and distances.speeds and distances.

Copernicus’ ModelCopernicus’ Model

Copernicus’ Model Ptolemy ModelCopernicus’ Model Ptolemy Model sun in center Earth in center sun in center Earth in center

KEPLER’S LAWSKEPLER’S LAWS

77Upon whose observations did Johannes Upon whose observations did Johannes

Kepler base his three laws of planetary Kepler base his three laws of planetary motion? motion? Tycho BraheTycho Brahe

Matching 8-10Matching 8-10

8. 8. eccentricity eccentricity 9. 9. ellipse ellipse 10. 10. orbital period orbital period

a. a. a closed curve whose a closed curve whose shape is determined by shape is determined by two points, or foci two points, or foci

b. b. the time required for a the time required for a body to complete a single body to complete a single orbitorbit

c. c. the degree of elongation the degree of elongation of an elliptical orbit of an elliptical orbit

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What does the What does the law of ellipses law of ellipses state?state?Keplar’s first law: Each planet orbits the sun in Keplar’s first law: Each planet orbits the sun in

a path called an ellipsea path called an ellipse

Shape of OrbitsShape of OrbitsPlanets orbit in an elliptical shapePlanets orbit in an elliptical shape

1212 In planetary orbits, one focus is located In planetary orbits, one focus is located

within the _________________, and no within the _________________, and no object is located at the other focus. object is located at the other focus. sunsun

1313How is eccentricity determined? How is eccentricity determined?

By dividing the distance between the foci of By dividing the distance between the foci of the ellipse by the length of the major axis.the ellipse by the length of the major axis.

1414What did Kepler discover about the orbit of What did Kepler discover about the orbit of

Mars? Mars? Mars moves fastest in its elliptical orbit when it Mars moves fastest in its elliptical orbit when it

is closest to the sun.is closest to the sun.

1515The law of equal areas states that equal The law of equal areas states that equal

areas are covered in equal amounts of areas are covered in equal amounts of time as an object orbits the ___________. time as an object orbits the ___________. SunSunKepler’s second lawKepler’s second law

1616Kepler’s third law, the law of periods, Kepler’s third law, the law of periods,

describes the relationship between the describes the relationship between the average distance of a planet from the sun average distance of a planet from the sun and the _____ ____ of the planet.and the _____ ____ of the planet.orbital periodorbital period

1717According to the law of periods, the cube According to the law of periods, the cube

of the average _________of a planet from of the average _________of a planet from the sun the sun is always proportional to the is always proportional to the square of the period.square of the period.distance (a)distance (a)

1818 What mathematical formula is used to What mathematical formula is used to

explain the law of periods? explain the law of periods? K x aK x a33 = p = p22

(a)(a) is the average distance of a planet from the is the average distance of a planet from the sunsun

(p) orbital period(p) orbital periodK is a constantK is a constant

Distance cubed = period squaredDistance cubed = period squared(almost?)(almost?)

1919The tendency of a stationary body to The tendency of a stationary body to

remain at rest or of a moving body to remain at rest or of a moving body to remain in motion until an outside remain in motion until an outside force force acts upon it is called ______________. acts upon it is called ______________. inertiainertia

2020Newton discovered that an outside force Newton discovered that an outside force

called _______________ causes the orbit called _______________ causes the orbit of a planet to curve. of a planet to curve. gravitygravity

2121The outer planets have longer periods of The outer planets have longer periods of

____________than the inner planets ____________than the inner planets because the because the outer planets are less outer planets are less affected by the sun’s gravitational pull.affected by the sun’s gravitational pull. revolutionrevolution

The EndThe End