Earth and the Solar System (Chp.37+38)

• Star


  An object that generates its own heat and light from nuclear fusion reactions. It is held together by its own gravity
• Planet


  Round object that orbits a star and has cleared its own orbit of other objects
• Terrestrial planets

  • Inner rocky planets: mercury, venus, earth, mars
  • Outer gas giant planets:Jupiter, saturn, uranus, neptune
• Asteroids

  • Small bodies that orbit the Sun but are not rounded
  • Found in Asteroid Belt and Kuiper Belt
• Comets 


  Small icy bodies that orbit the Sun

  Originate from Oort Cloud
• Astronomy 


  Study of the universe
• Origin

  1. 14 billion years ago a singularity started to expand
  2. This created the universe
  3. As it expanded it cooled and subatomic particules developed, which formed atoms
  4. By 13 billion years ago galaxies and stars formed and the familiar universe
• Evidence

  • Expansion of the universe
  • Cosmic background radiation
  • Proportions of heavy + light elements
• Galaxies 


  Galaxy is a collection of stats helf together by gravitational forces. Can be elliptical, spiral(M.W) or irregular shapes
• Light year 


  The distance light can travel in a year
• Black hole

  A singularity that has such gravitational pull matter and light cannot escape from it
• Life Cycle of a Star

  1. Formation: nebula condenses due to gravity, pressure and temperature increase, nuclear fusion starts (H -> He)
  2. Stability: Nuclear fusion reactions maintain the star as it emits radiation, including light.
  3. Expansion: Star expands in an effort to find more fuel. It cools and becomes a red giant.
  4. Death: Fuel runs out, nuclear reactions stop. Small star collapses to form white dwarves. Large stars explode in super novae and form neutron stars
• Space travel

  • 1957: Spudnik 1 & 2
  • 1965: Yari Gagarin
  • 1969: Neil Armstrong
  • 1972: Moon
• Benefits of space travel

  • Food safety and preservation
  • Insulation
  • GPS
  • Weather forecasting
  • Fire resistant material
• Dangers of space travel

  • Death
  • Bone density increasing
  • Muscle deterioration
  • Radiation: cancer
  • Weakens heart
• Earth structure

  • Core: solid inner core liquid outer core, magnetic field
  • Mantle: solid inner mantle and magma outer mantle
  • Crus: thin rocky surface broken into tectonic plates
  • Atmosphere: gases
• Movement

  • 24 hours for the Earth to rotate on its axis
  • 365 days for the Earth to orbit the Sun
  • Axis of the Earth rotation is 23.5° from the vertical (seasons)
• Winter and summer


  In winter the northen hemisphere points away from Sun and in summer it points towards the Sun
• The Moon


  A natural satellite, is a body that orbits another body
• Phases of Moon

  1. New moon: dark
  2. Waxing Cresent: light begins to appear (Right side)
  3. First Quarter: half the surface of the moon is lit(R.S)
  4. Waxing Gibbous: more than half of the surface is bright (R.S)
  5. Full moon: Whole surface is bright
  6. Waning Gibbous: more than half the surface is bright (Left side)
  7. Third Quarter: half the surface is in light(L.S)
  8. Waning Cresent: light begins to disappear from left side
• Tides

  • Gravity of the moon pulls the surface of the Earth towards it.
  • Liquid water is affected more than land
  • Water bulges towards the moon
  • At the other side of Earth a centrifugal force pulls water out the other side.
  • Therefore there is 2 low and 2 hight tides
• Eclipses

  • Lunar Eclipse occurs when the Moon falls in the Earth's shadow
  • Solar eclipse occurs when the Earth falls in the Moon's shadow