Lesson 1

• The Universe


  All of space and everything in it including stars, planets, and galaxies
• What the Universe refers to


  • All time
  • All space
  • All matter
  • All energy
• Parallel universe


  An area of space or a world that is similar to but separate from the one we live in
• Big Bang Theory


  How the universe started, and then made the stars and galaxies we see today
• Big Bang Theory


  1. Universe began as a very hot, small, and dense super force

  2. Universe formed about 13 billion years ago

  3. Universe is expanding and evolving
• Big Bang Theory


  • Best theory of the origin and evolution of the universe
  • Remarkably successful in explaining the expansion of the universe
  • Implies the universe has an infinite age
• Hubble's Law


  • All the galaxies exploded from a point in the past
  • The universe is expanding and the distance between the galaxies is continuously growing
• The Big Bang Theory is not the only plausible theory for the origin of the universe
• The universe has a beginning
• Galaxies appear to be moving away from us at speeds proportional to their distance
• If the universe was initially very hot, we should be able to find some remnant of this heat
• The abundance of hydrogen and helium in the observable universe supports the Big Bang model
• The universe continuously expanded for several years and the cloud of hydrogen and helium gases condensed to form stars, including the sun
• The Big Bang was not an explosion in space but an explosion of space
• The Big Bang was not an explosion of time - both space and time were created at the moment of the Big Bang
• Cosmological Principles


  • Homogeneous - same everywhere
  • Isotropic - same in all directions
• The universe has no edge
• The universe has no center
• Steady State Theory


  Universe is always expanding but maintaining a constant average density
• Hubble's Law
• Big Bang Theory