The Solar SystemThe Solar System

Chapter 24Chapter 24

Section 1Section 1

Earth Centered Models Earth Centered Models (Geocentric)(Geocentric)

Various models of the solar system with Various models of the solar system with Earth at the center.Earth at the center.Most commonly, the moon, the sun, the five Most commonly, the moon, the sun, the five

planets (Mercury, Venus, Mars, Jupiter, and planets (Mercury, Venus, Mars, Jupiter, and Saturn), and the stars were fixed in separate Saturn), and the stars were fixed in separate spheres that rotated around the earth.spheres that rotated around the earth.

Didn’t explain retrograde motion.Didn’t explain retrograde motion.

Earth Centered Models Earth Centered Models (Geocentric)(Geocentric)

Claudius Ptolemy Claudius Ptolemy Greek astronomer who lived 500 years after Greek astronomer who lived 500 years after

Aristotle (384 to 322 B.C.)Aristotle (384 to 322 B.C.)Proposed that all planets move in a series of Proposed that all planets move in a series of

small circles called epicycles as they revolve small circles called epicycles as they revolve around the Earth.around the Earth.The motion of the planet in its epicycle would make The motion of the planet in its epicycle would make

it appear to move backwards.it appear to move backwards.

Sun Centered Model (Heliocentric)Sun Centered Model (Heliocentric)

Published by Nicolaus Copernicus (a Published by Nicolaus Copernicus (a Polish astronomer) in 1543.Polish astronomer) in 1543.

Stated that the moon revolved around Stated that the moon revolved around the earth, but the earth and all the the earth, but the earth and all the planets revolved around the sun.planets revolved around the sun. Each planet revolved at a different speed Each planet revolved at a different speed

and a different distance from the sun.and a different distance from the sun.

Also stated that the daily movement of Also stated that the daily movement of the planets and the stars was due to the the planets and the stars was due to the rotation of the earth.rotation of the earth.

Support for Sun Centered ModelSupport for Sun Centered Model

Galileo GalilieiGalileo Galiliei Italian scientist in the 1600’s.Italian scientist in the 1600’s.Observed the motions of the planets Observed the motions of the planets

with the newly invented telescope.with the newly invented telescope.Collected evidence such as the Collected evidence such as the

phased of Venus which supported phased of Venus which supported the heliocentric model of the solar the heliocentric model of the solar system.system.

Mathematical Support of the Mathematical Support of the Sun Centered ModelSun Centered Model

Johannes Kepler (1571-1630)Johannes Kepler (1571-1630)Developed three laws to describe the Developed three laws to describe the

motion of planets:motion of planets:Law of EllipsesLaw of EllipsesLaw of Equal AreasLaw of Equal AreasLaw of PeriodsLaw of Periods

Law of EllipsesLaw of EllipsesAll planets orbit the sun in an elliptical All planets orbit the sun in an elliptical

path.path.

Law of Equal AreasLaw of Equal AreasDescribes the speeds at which planets Describes the speeds at which planets

travel around the sun.travel around the sun.Planets always travel through equal areas Planets always travel through equal areas

in equal periods of time.in equal periods of time.

Law of PeriodsLaw of PeriodsDescribes 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 orbital period of the planet.and the orbital period of the planet.The orbit period is the time required for the The orbit period is the time required for the

planet to make one revolution around the sun.planet to make one revolution around the sun.

Modern View of the Solar SystemModern View of the Solar System

Eight planetsEight planetsMercury, Venus, Earth, Mars, Jupiter, Saturn, Mercury, Venus, Earth, Mars, Jupiter, Saturn,

Uranus, NeptuneUranus, NeptuneAll planets along with many smaller All planets along with many smaller

objects orbit the sun.objects orbit the sun.The sun contains 99.86% of all mass The sun contains 99.86% of all mass

contained within the solar system.contained within the solar system.

Formation of the Solar SystemFormation of the Solar System

Nebular TheoryNebular TheoryProposed in 1796 by the French Proposed in 1796 by the French

mathematician Marquis Pierre Simon de mathematician Marquis Pierre Simon de Laplace.Laplace.

Stated that the sun and planets condensed Stated that the sun and planets condensed out of the same spinning nebula of gas, ice out of the same spinning nebula of gas, ice and dust at approximately the same time (4.6 and dust at approximately the same time (4.6 billion years ago).billion years ago).

Formation of the Solar SystemFormation of the Solar System

1.1. Formation of a slowly spinning cloud of Formation of a slowly spinning cloud of material.material.

2.2. Contraction of the cloud begins (possibly Contraction of the cloud begins (possibly caused by something similar to the explosion of caused by something similar to the explosion of a nearby star).a nearby star).

3.3. As the cloud contracts, more material is pulled As the cloud contracts, more material is pulled into the center of the cloud causing it to rotate into the center of the cloud causing it to rotate quicker.quicker.1.1. Higher density objects exert larger gravitational Higher density objects exert larger gravitational

forces.forces.

4.4. Eventually the cloud forms a flattened disk with Eventually the cloud forms a flattened disk with a dense area in the center.a dense area in the center.

Formation of the Solar SystemFormation of the Solar System

5.5. Temperatures in the cloud increase until Temperatures in the cloud increase until the core of the cloud is 10 million the core of the cloud is 10 million degrees Celsius and nuclear fusion degrees Celsius and nuclear fusion begins (this is the birth of the sun).begins (this is the birth of the sun).

1.1. Nuclear fusion occurs when lighter mass Nuclear fusion occurs when lighter mass atoms are fused into heavier mass elements atoms are fused into heavier mass elements (such as hydrogen into helium).(such as hydrogen into helium).

2.2. A slight mass is converted into energy in this A slight mass is converted into energy in this process.process.

Formation of the Solar SystemFormation of the Solar System

6.6. Matter that is not pulled into the center of the Matter that is not pulled into the center of the cloud begin to form clumps (planetisimals), cloud begin to form clumps (planetisimals), with each clump getting larger as it collides with each clump getting larger as it collides with other clumps (forming protoplanets and with other clumps (forming protoplanets and eventually planets).eventually planets).

1.1. Close to the sun, temperatures are so high that Close to the sun, temperatures are so high that lighter elements such as hydrogen, helium, lighter elements such as hydrogen, helium, methane, and ammonia were vaporized, causing methane, and ammonia were vaporized, causing the inner planets to be terrestrial and the outer the inner planets to be terrestrial and the outer planets to be gaseous.planets to be gaseous.