2Questions??What are some theories about how our solar system began?
3The Nebular Hypothesis solar nebular a rotating cloud of gas and dust from which the sun and planets formedIn 1796, French mathematician Pierre Simon, advanced a hypothesis now known as the nebular hypothesis.
5The Nebular Hypothesis The sun is composed of about 99% of all of the matter that was contained in the solar nebula.planetesimal a small body from which a planet originated in the early stages of development of the solar system
6Nebular HypothesisSome planetesimals joined together through collisions and through the force of gravity to form larger bodies called protoplanets.Protoplanets’ gravity attracted other planetesimals, collided, and added their masses to the protoplanets
8Nebular Hypothesis Step 1: Step 2: Step 3: The young solar nebula starts to collapse due to gravity.Step 2:As it rotates, it flattens and becomes warmer near the center…this is where our sun formed.Step 3:Planetesimals form within the swirling disk
9Nebular Hypothesis Step 4: Step 5: Step 6: As planetesimals grow, their gravitational pull increases. Larger planets collect mostly dust and gas.Step 5:Small planetesimals hit larger ones and planets begin to grow.Step 6:Left over dust and gas leave solar nebula and our solar system is formed!
10The Planets The Inner Planets: The outer Planets: Mercury, Venus, Earth, MarsSmaller, rockier, more dense than outer planetsContain heavier elements like nickel and ironThe outer Planets:Jupiter, Saturn, Uranus and NeptuneComposed of lighter elements such as helium, hydrogen and their ices (water ice, ammonia ice & methane ice)Called gas giants b/c made of gas and have low density
11Pluto – The Different Planet Farthest and smallest planet (smaller than Earth’s moon)Ice ball made of frozen gasses and rocksScientist do not believe that Pluto qualifies as a real planet.Question?? How is Pluto different from the outer planets?Unlike the other outer planets, Pluto is very small and is composed of rock and frozen gas, instead of thick layers of gases.
12The Formation of Solid Earth First, Earth was very hot, then Earth cooled to form three distinct layers.Differentiation – denser materials sank to the center and lighter materials were forced to the outer layers.Center: dense core of iron and nickelMantel: surrounds core, think layer of iron & magnesium rich rockCrust: outermost layer, less dense, silica rich rock
14Earth’s Atmosphere The atmosphere formed because of differentiation. Earth’s gravity is too weak to hold high concentrations of hydrogen and helium gases and is blown away by solar winds.OutgassingOutgassing formed a new atmosphere as volcanic eruptions released large amounts of gasesThe ozone formed from remaining oxygen molecules after solar radiation caused ammonia and some water vapor to break down.
17Earth’s Present Atmosphere The ozone collected in a high atmospheric layer around Earth and shielded Earth’s surface from the harmful ultraviolet radiation of the sun.Organisms, such as cyanobacteria and early green plants, could survive in Earth’s early atmosphere by using carbon dioxide during photosynthesisThese organisms produced oxygen as a byproduct of photosynthesis and helped slowly increase the amount of oxygen in the atmosphere.
18Question??How did green plants contribute to Earth’s present-day atmosphere?Green plants release free oxygen as part of photosynthesis, which caused the concentration of oxygen gas in the atmosphere to gradually increase.
19Formation of Earth’s Oceans Were the first oceans fresh water or salt water?Fresh waterAs rain continued to fall, rocks were dissolved into the oceans.As evaporation occurred, some of the chemicals from the rocks combined to form salts, making the oceans increasingly more salty.
20The Ocean’s Effect on the Atmosphere The ocean affects global temperature by dissolving carbon dioxide from the atmosphere.Since Earth’s early atmosphere contained less carbon dioxide than today, Earth’s early climate was probably cooler than the global climate is today.
21Multiple Choice Chapter 27 Small bodies that join to form protoplanets in the early stages of the development of the solar system areA. planetsB. solar nebulasC. plantesimalsD. gas giants
22Multiple Choice, continued Chapter 27Multiple Choice, continuedSmall bodies that join to form protoplanets in the early stages of the development of the solar system areA. planetsB. solar nebulasC. plantesimalsD. gas giants
23Multiple Choice, continued Chapter 27Multiple Choice, continued2. Scientists hypothesize that Earth’s first oceans were made of fresh water. How did oceans obtain fresh water?A. Water vapor in the early atmosphere cooled and fell to Earth as rain.B. Frozen comets that fell to Earth melted as they traveled through the atmosphere.C. As soon as icecaps formed, they melted because Earth was still very hot.D. Early terrestrial organisms exhaled water vapor, which condensed to form fresh water.
24Multiple Choice, continued Chapter 27Multiple Choice, continued2. Scientists hypothesize that Earth’s first oceans were made of fresh water. How did oceans obtain fresh water?A. Water vapor in the early atmosphere cooled and fell to Earth as rain.B. Frozen comets that fell to Earth melted as they traveled through the atmosphere.C. As soon as icecaps formed, they melted because Earth was still very hot.D. Early terrestrial organisms exhaled water vapor, which condensed to form fresh water.
25Multiple Choice, continued Chapter 27Multiple Choice, continuedThe original atmosphere of Earth consisted ofA. nitrogen and oxygen gasesB. helium and hydrogen gasesC. ozone and ammonia gasesD. oxygen and carbon dioxide gases
26Multiple Choice, continued Chapter 27Multiple Choice, continuedThe original atmosphere of Earth consisted ofA. nitrogen and oxygen gasesB. helium and hydrogen gasesC. ozone and ammonia gasesD. oxygen and carbon dioxide gases
27Multiple Choice, continued Chapter 27Multiple Choice, continuedScientists think that the core of Earth is made of moltenF. iron and nickelG. nickel and magnesiumH. silicon and nickelI. iron and silicon
28Multiple Choice, continued Chapter 27Multiple Choice, continuedScientists think that the core of Earth is made of moltenF. iron and nickelG. nickel and magnesiumH. silicon and nickelI. iron and silicon
29Short Response Chapter 27 6. What four planets make up the group known as the inner planets?
30Early Models of the Solar System Geocentric = ?Earth centered solar systemAristotle proposed this ideaSun, stars and planetsrevolved around the Earth
31Claudius Ptolemy Proposed changes to Aristotle’s model Thought that planets moved in small circles, called epicycles, as they revolved around the Earth.Explained why some planets seemed to move backwards at times: retrograde motion.The word ”retrograde” derives from the Latin words “retro” meaning backwards, and “gradus”, meaning step
32A circular orbit in a circular orbit. This satisfied the Greek’s ideaof an Earth centered Universeand the idea that the motion ofthe heavenly bodies moved inperfect circles.
33Early Models of the Solar System Heliocentric = ?Sun centered solar systemCopernicus proposed this ideaPlanets revolved around thesun but at different speedsand distances from the sun.
34Kepler’s Laws Law of Ellipses eccentricity - the degree of elongation of an elliptical orbit(symbol, e)The law of ellipses states that each planet orbits the sun in a path called an ellipse, not in a circle.
35Kepler’s Laws Law of Equal Areas The law of equal areas describes the speed at which objects travel at different points in their orbit. It states that equal areas are covered in equal amounts of time as an object orbits the sun.When the object is near the sun, it moves relatively rapidly. When the object is far from the sun, it moves relatively slowly.
37Kepler’s Laws Law of Periods orbital period - the time required for a body to complete a single orbitThe law of periods describes the relationship between the average distance of a planet from the sun and the orbital period of the planet
38Kepler’s Third LawThe mathematical equation, K x a3 = p2, where K is a constant, describes this relationship.When distance is measured in astronomical units (AU) and the period is measured in Earth years,K = 1 and a3 = p2.a = average distance from the sunp = period
39Example: a³ = (11.9)² a³ = 142 a = 5.2 AU a³ = p² Jupiter has an orbital period of 11.9 Earth years.Find the average distance.a³ = p²a³ = (11.9)²a³ = 142a = 5.2 AU
40Kepler’s Laws explained by Newton: inertia the tendency of an object to resist being moved or, if the object is moving, to resist a change in speed or direction until an outside force acts on the objectWho discovered gravity?NewtonGravity - an attractive force that exists between any two objects in the universe.While gravity pulls an object towards the sun, inertia keeps the object moving forward in a straight line. This forms the ellipse of a stable orbit.The gravitational pull is strongest closer to the sun, and weakest further from the sun.