The Origin and structure of the earth

• How scientists study the universe

  Principles used to understand the beginning of the universe
• Hypothesis


  A proposition that can be tested by research
• Model


  A physical, mathematical, or conceptual representation of a system of ideas that is difficult to observe directly
• Theory


  A scientifically acceptable general principle offered to explain a phenomena
• Law


  A description of an observed phenomenon
• Theories

  • Big Bang Theory
  • Steady State Theory
  • Oscillating Universe Theory and Eternal Inflation Theory
  • Nebular Hypothesis and Condensation Theory
• Big Bang Theory


  A massive blast that allowed all the universe's known matter and energy—even space and time themselves—to spring from some ancient and unknown type of energy
• Big Bang Theory


  1. The universe expanded with incomprehensible speed from its pebble sized origin to astronomical scope

  2. The expansion has apparently continued, but much more slowly, over the ensuing billions of years
• Proponent of Big Bang Theory

  Georges Lemaitre in the 1920s
• Steady State Theory


  The universe is assumed to have average properties that are constant in space and time so that new matter must be continuously and spontaneously created to maintain average densities as the universe expands
• Proponents of Steady State Theory

  Sir James Jeans in 1920s, Fred Hoyle, Thomas Gold, and Hermann Bondi in 1948
• Oscillating Universe Theory and Eternal Inflation Theory


  Due to the amount of gravity in the universe, the matter moving outward following the Big Bang will eventually be slowed and pull back toward the center of the universe resulting in the Big Crunch. Another Big Bang would follow the Big Crunch, giving rise to a new universe of possibilities.
• Proponent of Oscillating Universe Theory

  Albert Einstein in 1920s
• Nebular Hypothesis and Condensation Theory


  The solar system was derived from the condensation of an enormously dispersed gaseous atmosphere surrounding the sun. The increased rotational velocity of this atmosphere during condensation would throw off part of the gas as a ring and materials of each ring gradually assembled into a gaseous globe, which eventually became a solid planet revolving around the sun.
• Proponents of Nebular Hypothesis and Condensation Theory

  Immanuel Kant in 1755, Laplace in 1796
• Layers of the Earth

  • Crust
  • Mantle
  • Core
• Crust


  • Brittle outermost layer of the planet, variable thickness from 5-10 km in ocean basins to 25-70 km in continents
• Mantle


  • Dense layer of the Earth composed only of molten silicate rocks
• Core


  • Hottest layer of the Earth, source of the Earth's magnetic field, has liquid outer core and solid inner core made of iron and nickel
• Subsystems of the Earth

  • Lithosphere
  • Hydrosphere
  • Atmosphere
  • Biosphere
• Lithosphere


  The rocky crust of the Earth, inorganic and composed mainly of different kinds of minerals
• Hydrosphere


  Composed of all the waters, which circulate in the Earth, including oceans, seas, rivers, lakes, and moisture in the air
• Atmosphere


  The mass of air surrounding the planet, subdivided into different layers of different densities, comprised of 79% Nitrogen, fewer than 21% Oxygen, and remaining shared by Carbon Dioxide and other gases
• Biosphere


  Comprises all living organisms, from the smallest bacteria to the largest whale