Observing the Solar SystemObserving the Solar System

Chap 16, Sec 1Chap 16, Sec 1

Chap 16 Sec 1 Essential Chap 16 Sec 1 Essential QuestionsQuestions

1.1. What are the geocentric and What are the geocentric and heliocentric systems?heliocentric systems?

2.2. How did Copernicus, Galileo, and How did Copernicus, Galileo, and Kepler contribute to our knowledge Kepler contribute to our knowledge of the solar system?of the solar system?

3.3. What objects make up the solar What objects make up the solar system?system?

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StarsStars Ancient Greeks noticed the stars are grouped Ancient Greeks noticed the stars are grouped

together in patterns we call constellations. together in patterns we call constellations. The stars in a constellation stay the same The stars in a constellation stay the same night after night, and year after year.night after night, and year after year.

There are 88 There are 88 constellationsconstellations The Greeks also noticed several “stars” that The Greeks also noticed several “stars” that

seemed to wander slowly among the starsseemed to wander slowly among the stars The Greeks named these lights planets (which is The Greeks named these lights planets (which is

a Greek word for wanderers)a Greek word for wanderers) The Romans later named the planets they could The Romans later named the planets they could

see: Mercury, Venus, Mars, Jupiter, and Saturnsee: Mercury, Venus, Mars, Jupiter, and Saturn Look on page 554 at the time lapse photo. Look on page 554 at the time lapse photo.

This was made while viewing the circumpolar This was made while viewing the circumpolar constellations that circle around the north constellations that circle around the north star.star.

Geocentric SystemGeocentric System

Ancient Greeks believed Earth (Greek: geo) Ancient Greeks believed Earth (Greek: geo) is at the center of the revolving planets and is at the center of the revolving planets and starsstarsThis is known as the Geocentric systemThis is known as the Geocentric systemPtolemy further developed the geocentric model Ptolemy further developed the geocentric model

to show planets moving on small circles that to show planets moving on small circles that move on bigger circlesmove on bigger circles

His model was incorrect, but did explain the His model was incorrect, but did explain the motions observed in the sky fairly accuratelymotions observed in the sky fairly accurately

This model was widely accepted for nearly 1500 This model was widely accepted for nearly 1500 years after Ptolemy introduced ityears after Ptolemy introduced it

The The Geocentric Geocentric

ModelModel

Heliocentric SystemHeliocentric System

Another ancient Greek explanation for the Another ancient Greek explanation for the motion of the planets said the sun is at the motion of the planets said the sun is at the center and Earth and the other planets center and Earth and the other planets revolve around itrevolve around itThis is known as the heliocentric system This is known as the heliocentric system

(helios is Greek for sun)(helios is Greek for sun)This explanation wasn’t widely accepted This explanation wasn’t widely accepted

because so many believed the Earth had to because so many believed the Earth had to be at the centerbe at the center

The The HeliocentricHeliocentric

ModelModel

Nicolaus CopernicusNicolaus Copernicus

Nicolaus CopernicusNicolaus Copernicus

In 1543 (almost 1500 years after In 1543 (almost 1500 years after Ptolemy’s geocentric work) Copernicus Ptolemy’s geocentric work) Copernicus was able to work out the arrangement of was able to work out the arrangement of the known planets and how they move the known planets and how they move around the sun.around the sun.

Most people couldn’t accept this new idea Most people couldn’t accept this new idea – they would need proof first– they would need proof firstBy the way, Copernicus was PolishBy the way, Copernicus was Polish

Galileo GalileiGalileo Galilei

Galileo GalileiGalileo Galilei

Galileo made two important discoveries using Galileo made two important discoveries using the newly invented telescope that supported the the newly invented telescope that supported the heliocentric modelheliocentric model In 1610 he discovered four moons revolving around In 1610 he discovered four moons revolving around

JupiterJupiterThis proves not everything in space revolves around EarthThis proves not everything in space revolves around Earth

He discovered Venus goes through a series of He discovered Venus goes through a series of phases similar to our Moon.phases similar to our Moon.

Venus would not have a full set of phases if it encircled Venus would not have a full set of phases if it encircled EarthEarth

Just so you know, Galileo was ItalianJust so you know, Galileo was Italian

Tycho BraheTycho Brahe

Tycho BraheTycho Brahe

In the late 1500s Tycho Brahe and his In the late 1500s Tycho Brahe and his assistants observed and recorded the assistants observed and recorded the positions of the planets (this would be positions of the planets (this would be important later in changing the model important later in changing the model developed by Copernicus)developed by Copernicus)

They did this without telescopes because They did this without telescopes because they hadn’t been invented yetthey hadn’t been invented yet

Brahe was DanishBrahe was Danish

Johannes KeplerJohannes Kepler

Johannes KeplerJohannes Kepler

Kepler was an assistant to Tycho Brahe Kepler was an assistant to Tycho Brahe who died in 1601.who died in 1601.

Kepler carefully analyzed all the Kepler carefully analyzed all the observations collected under Brahe and observations collected under Brahe and eventually found that the orbit of each eventually found that the orbit of each planet is an ellipse (a flattened oval)planet is an ellipse (a flattened oval)

This disproved the belief that all planets This disproved the belief that all planets move in perfect circlesmove in perfect circles

He was GermanHe was German

Modern DiscoveriesModern Discoveries Today we know the solar system consists of the sun, Today we know the solar system consists of the sun,

the planets and their moons, and several kinds of the planets and their moons, and several kinds of smaller objects that revolve around the sun (such as smaller objects that revolve around the sun (such as comets and asteroids)comets and asteroids) A moon is a natural satellite that revolves around a A moon is a natural satellite that revolves around a

planetplanet We have telescopes on Earth and orbiting in spaceWe have telescopes on Earth and orbiting in space We have sent astronauts to the moon and launched We have sent astronauts to the moon and launched

many space probes to explore our solar systemmany space probes to explore our solar system Our understanding of the solar system continues to Our understanding of the solar system continues to

grow every day.grow every day. I wonder what will be discovered during your lifetime!I wonder what will be discovered during your lifetime!

Essential Questions AnsweredEssential Questions Answered1.1. What are the geocentric and heliocentric What are the geocentric and heliocentric

systems?systems?The geocentric system said Earth is at the center of the The geocentric system said Earth is at the center of the

revolving planets and stars (including the sun and moon).revolving planets and stars (including the sun and moon).The heliocentric system says the sun is at the center of our The heliocentric system says the sun is at the center of our

solar system and is surrounded by planets and their solar system and is surrounded by planets and their moons.moons.

2.2. How did Copernicus, Galileo, and Kepler How did Copernicus, Galileo, and Kepler contribute to our knowledge of the solar contribute to our knowledge of the solar system?system?Copernicus – further developed the heliocentric system by Copernicus – further developed the heliocentric system by calculating the arrangement of the planets and how they calculating the arrangement of the planets and how they move around the sunmove around the sunGalielo – used the newly invented telescope to make Galielo – used the newly invented telescope to make discoveries that supported the heliocentric modeldiscoveries that supported the heliocentric modelKepler – discovered the orbit of each planet is an ellipseKepler – discovered the orbit of each planet is an ellipse

3.3. What objects make up the solar system? What objects make up the solar system? The sun, the planets and their moons, and several kinds of The sun, the planets and their moons, and several kinds of smaller objects that revolve around the sun.smaller objects that revolve around the sun.