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Chapter 4 – Origins of Cosmic Structures and Chemical Elements

Chapter 4 – Origins of Cosmic Structures and Chemical Elements. Steady State or Evolutionary Cosmology. Steady State Universe Theory is no longer accepted. Evolutionary Universe (Big Bang) Theory describes the origin of the universe. Figure 4.CO: Messier 104 (Sombrero galaxy).

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Chapter 4 – Origins of Cosmic Structures and Chemical Elements

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  1. Chapter 4 – Origins of Cosmic Structures and Chemical Elements

  2. Steady State or Evolutionary Cosmology • Steady State Universe Theory is no longer accepted. • Evolutionary Universe (Big Bang) Theory describes the origin of the universe.

  3. Figure 4.CO: Messier 104 (Sombrero galaxy) Courtesy of NASA/JPL-Caltech and The Hubble Heritage Team (STScI/AURA)

  4. Inflation • The universe is expanding. Fig 4.1 pg 66 Courtesy of NASA/WMAP Science Team

  5. Table 4.01: The first 100 seconds in the life of the universe

  6. The First 380,000 Years • The temperature of the “plasma” was initially too hot for electrons to combine with protons. • Once the temperature cooled enough, atoms could form. • Occurred in the “epoch of recombination,” about 380,000 years after the Big Bang. • Radiation was released, now know as the cosmic microwave background (CMB) • The universe is ~13.7 billion years old.

  7. First Lights and the Formation of Galaxies • The first stars appeared ~200 My after the Big Bang • Gravity brings stars together into galaxies • Galaxies are named according to their shape. • Each galaxy merger leads to the formation of more stars.

  8. Formation of Stars and Chemical Elements • 4 H+ join to form He, releasing energy. • Stars live on this reaction 90%+ of their lives. • A red giant is a star that has exhausted its supply of H+ fuel. • The core begins to condense. • When the core reaches a critical mass, it collapses. • It can become a neutron star, or a black hole. • Supernova is the explosion.

  9. Galactic Chemical Evolution • The most common atom is hydrogen, left over from the Big Bang. • Many biologically important atoms are created by burning of elements in stars. Fig 4.4 pg 71

  10. Shape and Future of the Universe • The average density of the universe is close to critical density. • Evidence suggests the universe is flat. • It is likely to expand forever.

  11. Figure 5.01: Stages during the condensation of the solar nebula into the solar planetary system

  12. Origin of Earth's Atmosphere • First atmosphere • Hydrogen and Helium, blown away by powerful winds from Sun • Secondary Atmosphere • 4.2 – 3.8 Bya • Volcanic output • Water vapor, carbon dioxide, carbon monoxide, nitrogen, ammonia, methane, hydrochloric acid, and hydrogen sulfide • Methane may have been byproduct of single-celled microbes called methanogens.

  13. Origin of Earth's Atmosphere • Liquid Water • Formed when Earth cooled • C02 absorbed into oceans • Reducing • Excess hydrogen compounds provided electrons to oxidizing agents

  14. Oxygen • Currently makes up 21% volume of atmosphere • Began increasing 2.3 Bya • Due to aquatic and photosynthetic cyanobacteria • Initially reacted with ammonia and iron • Then surplus began accumulating in atmosphere

  15. Table 5.01: Present composition of Earth's atmosphere

  16. Origin of Earth's Structure • Earth has four major layers • Inner Core • Outer Core • Mantle • Crust Fig 5.2 pg 80

  17. Earth's Core • As planetesimals coalesced to form the Earth • Collisions and radioactive decay increased temperature • Partially molten • Heavy material (iron, nickel) sank inwards • Core 2,090 km thick • Outer Core • Responsible for Earth's magnetic field • Magnetosphere • Shields planet from incoming radiation

  18. Earth's Lithosphere - Mantle & Crust • Mantle • 2,900 km thick layer of rock • 80% of Earth's volume • Partly plastic, ductile • From heat of radioactive decay and compression • Crust • Floats on mantle • Separated by Moho (Mohorovicic) discontinuity • Continental Crust, Older • Oceanic Crust, Younger Fig 5.3 pg 80

  19. Earth's Crust • Three types of Rocks • Igneous : formed from molten rock (magma) • Granite – magma cools deep in crust • Lava – magma deposited on surface • 65% of Earth's Crust • Sedimentary : Particles of eroded igneous and other rocks, volcanic dust. • Sandstone, Limestone • 8% of Earth's Crust • Metamorphic : Rocks that have been transformed by excessive heat, pressure or chemical interactions. • Marble, Slate • 27% of Earth's Crust

  20. Table 5.02: Some basic facts and figures concerning Earth

  21. Origin of the Moon • Big Splash Theory • Planetesimal the size of Mars crashed into Earth on oblique angle • Part of the planetesimal and debris from Earth rebounded in space, coalesced • Gravity held moon to Earth

  22. Geological Dating • Relative Dating • Law of Superposition • Youngest layers of strata on top • Oldest layers of strata on bottom • Layers can be identified by fossils • Lengths of time can only be estimated • Phanerozoic Eon (Phanero, visible & zoon, life) Fig 5.5 pg 83

  23. Table 5.03: Geological ages and associated organic events

  24. Radiometric Dating • Isotopes • A form of an element • Variations in number of neutrons • Number of protons dependent on element • Decay over time, releasing energy • Radiometric Dating • Half-life of isotope, time required to transform ½ of material • Provides ability to determine specific age of some rocks Fig 5.6 pg 86

  25. Table 5.04: Radioactive isotopes used in dating

  26. Origin of the Continents: Continental Drift • Pangaea • Large super-continent that began to break apart 235 • Evidence: • Fit of Continents • Similarity of rocks and fossils • Palaeomagnetism Fig 5.9 pg 89 Fig 5.8 pg 88

  27. Paleomagnetism • Ferrous material magnetizes in cooling magma records • Records location and direction of magnetic field • Record of Earth's poles used to reconstruct continents location and movement through geological time Fig 5.10 pg 90

  28. Figure 5.11: Diagrammatic sections through an oceanic ridge

  29. Plate Tectonics • Tectonic Plates • Eight major plates have been identified • Plates separate • Lava creates oceanic ridges is space between moving plates • Plates slide past each other along fault lines • Plates collide • Subduction of one, uplift of other results in mountain building • Pangaea broke up as tectonic plates began to move • Separation of landmasses influenced biological evolution Fig 5.12 p 92

  30. Figure 5.14: The major geological plates and their boundaries (From Cosmos, Earth and Man: A Short History of the Universe by P. Cloud, 1978, Fig. 11, p. 82. Reprinted by permission.)

  31. Figure 5.15a: Collision of two plates, both with oceanic lithospheres

  32. Figure 5.15b: Collision of two plates, one oceanic and one continental

  33. Figure 5.15c: Collision of two plates, both with continental lithosphere

  34. Figure 5.16a: Prototheria (monotremes)

  35. Figure 5.16b: Metatheria (marsupials)

  36. Figure 5.16c: Eutheria (placentals)

  37. Biological Consequences of Plate Tectonics • Separation of organisms that were previously associated, results in unique evolutionary pathways • Mammals • Hairy skin, mammary glands • Prototheria (montremes) • Duckbilled platapus • Metatheria (marsupials) • Kangaroos • Eutheria (placental mammals) • Dogs, cats, humans Fig 5.17 pg 96

  38. Origin of the Planets • Condensation Theory, Nebular Hypothesis • Solar System formed from mass of dust and gas • Started to condense 5-5.6 Bya • Center began to heat, to form Sun 4.6 Bya • Accretion Disk • Surrounding early sun • Planetesimals formed from condensation • Protoplanets and Planets formed from collisions of planetesimals Fig 5.1 pg 77

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