27.1 and 27.2

Formation of the Solar System& Models of the Solar System

Section 27.1 & 27.2

Nebular Hypothesis· leading theory on how our solar system formed

solar system - sun and all the planets and other bodies that rotate around the sun

planet - any primary body that orbits the sun

· states that the sun and planets condensed at about the same time out of a solar nebula

solar nebula - a rotating cloud of gas and dust from which the sun and planets formed

occurred approximately 4.6 billion years agoproposed by Pierre-Simon marquis de Laplace

Formation of Sun & Planets· sun formed in the center when temperatures were high enough for hydrogen fusion to occur (10,000,000 C)· planets formed in outer regions

planetesimals (small, early stages) collisions and gravity produced protoplanets (large, middle stage) collisions and gravity produced planets (smaller and denser than protoplanets)

· inner planets - layeredless dense material on outside (rocky surface)more dense material on inside (metallic core)

· outer planets - gas giantscolder temperatures means they did not lose their

lighter elements (hydrogen and helium)

1 The hypothesis that states that the sun and the planets developed out of the same cloud of gas and dust is called the

A Copernicus hypothesis

B solar hypothesis

C nebular hypothesis

D Galileo hypothesis

Formation of Solid Earth· early Earth was hot enough to melt iron· differentiation (differences in density) led to the creation of Earth's three layers (crust, mantle, core)

heavy elements sank to middle and lighter elementsstayed on surface

Formation of Earth's Atmosphere· also formed through differentiation· original atmosphere primarily hydrogen and helium (light gases)

Earth's gravity not strong enough and they were blown away by solar wind

· outgassing created a new atmospherevolcanic eruptions released gases into the air (water

vapor, CO2, N2, CH4, SO2, and ammonia)created ozone layer

· current atmosphere resulted from photosynthesisincreased O2 levelsoccurred about 2 billion years ago

27.1 and 27.2

Formation of Earth's Ocean· icy bodies collided with Earth· their water became part of our atmosphere· water vapor condensed and formed rain· liquid water collected on Earth's surface· first oceans were probably freshwater

dissolved solids (including salt) slowly accumulated through runoff and evaporation

2 Young Earth formed a core, mantle, and crust in a process called

A layering

B settling

C dispersion

D differentiation

3 The first atmosphere on Earth contained a large amount of

A helium

B oxygen

C carbon dioxide

D methane

Early Models of the Solar System· early Greeks

Aristotle - geocentric model (sun, stars, moons, and planets revolved around the Earth)

Claudius Ptolemy (130 CE) - planets move in epicycle (orbit in small circles)

· Nicolaus Copernicus (1543 CE)heliocentric model (planets revolved around the sun

at different speeds and distances)· Galileo Galilei (1564-1642)

created the telescopeproved objects can revolve around objects other

than Earth (we were NOT the center of the universe)Catholic Church has him banished

Aristotle - geocentric model

Ptolemy - epicycles

Copernicus - heliocentric model

Early Models of the Solar System· Taycho Brahe (1576)

made observations of the solar system with his own instruments

· Johannes Kepler (1619)student of Brahedetermined planets' positions and orbits around the

sun accuratelydeveloped Kepler's Laws of Planetary Motion

sun is center and planets revolve in elliptical orbitsplanets move faster when their orbit brings them closer

to the sunmathematical formula to determine distance from sun

· Sir Isaac Newton (1668)described how gravity and inertia create a stable,

elliptical orbit

27.1 and 27.2

4 Copernicus's model of the solar system is

A geocentric

B ethnocentric

C heliocentric

D lunocentric

5 Who discovered that planets have an elliptical orbit?

A Aristotle

B Brahe

C Ptolemy

D Kepler

6 Scientists estimate that the solar system originated as a solar nebula, and the sun began to produce its own energy through nuclear fusion approximately how many years ago?

A 50 million years

B 500 million years

C 1 billion years

D 5 billion years