Big Bang

• The most popular theory of our universe's origin centers on a cosmic cataclysm unmatched in all of history—the Big Bang
• Before the big bang, scientists believe, the entire vastness of the observable universe, including all of its matter and radiation, was compressed into a hot, dense mass just a few millimeters across
• Big bang proponents suggest that some 10 billion to 20 billion years ago, a massive blast allowed all the universe's known matter and energy—even space and time themselves—to spring from some ancient and unknown type of energy
• The expansion has apparently continued, but much more slowly, over the ensuing billions of years
• Georges Lemaitre


  Belgian priest who first suggested the Big Bang Theory in the 1920s
• Edwin Hubble


  Made observations that galaxies are speeding away from us in all directions
• Cosmic microwave background radiation


  Tangible remnant of leftover light from the big bang

  
• The Big Bang Theory leaves several major questions unanswered, including the original cause of the Big Bang itself
• Astronomers have acquired the first direct evidence that gravitational waves rippled through our infant universe during an explosive period of growth called inflation
• NASA-developed detector technology on the BICEP2 telescope at the South Pole, in collaboration with the National Science Foundation, was used to make this discovery

  
• Our universe burst into existence in an event known as the Big Bang 13.8 billion years ago
• Moments later, space itself ripped apart, expanding exponentially in an episode known as inflation
• 1. mode polarization


  Characteristic swirly pattern in polarized light produced by gravitational waves
• The BICEP2 team used novel superconducting detectors to produce compelling evidence for the B-mode signal, providing the strongest support yet for cosmic inflation

  
• Nebular Hypothesis


  Theory that the solar system developed from the condensation of an enormously dispersed gaseous atmosphere surrounding the sun

  
• Planetesimal Theory


  Theory that the planetary system was formed from materials removed from the sun by tidal action caused by a passing star

  
• Dust Cloud Theory


  Theory that the nebula was assumed to have a composition mainly of hydrogen and helium, with only 1% of heavier elements

  
• Protoplanet Hypothesis


  Theory that the original nebula was so massive that on further contraction and flattening, it broke into separate clouds or protoplanets

  
• The Earth has several structures that give its shape and form, including the crust, mantle, and core

  
• Crust


  • Brittle outermost layer of the planet, with variable thickness ranging 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, always in perpetual convection motion due to core heating
• Solar system


  Built upon several layers of materials left behind during the stellar formation of the sun

  
• Terrestrial planets

  • Mercury
  • Venus
  • Earth
  • Mars
• Gas giants


  • Jupiter
  • Saturn
  • Uranus
  • Neptune
• Earth's structure

  • Crust
  • Mantle
  • Core

  
• Crust


  • Brittle outermost layer of the planet
  • Variable thickness ranging from 5-10 km from ocean basins to 25-70 km from continents

  
• Mantle


  • Dense layer of the Earth composed only of molten silicate rocks
  • In perpetual convection motion due to core heating
  • Varies in physical characteristics with depth

  
• Core


  • Hottest layer of the Earth
  • Source of the Earth's magnetic field
  • Has two layers, both made from iron and nickel
• Parts of the Earth

  • Lithosphere
  • Hydrosphere
  • Biosphere
  • Atmosphere
• Lithosphere


  The rocky crust of the Earth, including the uppermost mantle and the crust