Earth Sciences and Astronomy

Earth's Structure

• The Earth is composed of several layers:
  • Crust: outermost solid layer, varied in thickness and composition
  • Mantle: thick layer of hot, viscous rock beneath the crust
  • Outer Core: liquid iron-nickel alloy, responsible for generating magnetic field
  • Inner Core: solid, iron-nickel alloy at the center of the Earth

Plate Tectonics

• Theory that explains the movement of the Earth's crust:
  • Lithosphere: broken into several large plates that float on the mantle
  • Plates move relative to each other, resulting in geological activity:
    • Divergent motion: plates move apart, new crust forms
    • Convergent motion: plates collide, resulting in subduction or collision
    • Transform motion: plates slide past each other horizontally

Earth's Water Systems

• Hydrologic cycle: continuous process of water circulation between the Earth and atmosphere:
  • Evaporation: water evaporates from oceans, lakes, and rivers
  • Condensation: water vapor cools, forming clouds and precipitation
  • Runoff: precipitation that flows over the land, returning to bodies of water
• Oceans:
  • Cover approximately 71% of the Earth's surface
  • Salinity: measure of salt concentration in seawater
  • Ocean currents: driven by wind, tides, and thermohaline circulation

Earth's Atmosphere

• Composition:
  • Nitrogen (78%): dominant gas
  • Oxygen (21%): essential for life
  • Other gases: argon, carbon dioxide, water vapor, and others
• Atmospheric layers:
  • Troposphere: lowest layer, where weather occurs
  • Stratosphere: stable layer, where ozone layer is located
  • Mesosphere: layer where meteors burn up
  • Thermosphere: layer where aurorae occur
  • Exosphere: outermost layer, where atmosphere interacts with space

Space Science

• Celestial bodies:
  • Stars: massive, luminous balls of gas
  • Galaxies: large systems of stars, gas, and dust
  • Planets: rocky or gaseous bodies that orbit stars
  • Moons: natural satellites that orbit planets
• Solar System:
  • Consists of 8 planets (Mercury to Neptune), 5 dwarf planets, and other smaller bodies
  • Sun: center of the Solar System, providing light and heat
  • Asteroid belt: region between Mars and Jupiter, containing small rocky bodies
  • Kuiper belt: region beyond Neptune, containing icy bodies and comets

Astronomy and Space Exploration

• Telescopes: instruments used to study celestial objects:
  • Reflector telescopes: use mirrors to focus light
  • Refractor telescopes: use lenses to focus light
• Space exploration:
  • NASA: National Aeronautics and Space Administration (USA)
  • Spacecraft: vehicles designed to travel through space
  • International Space Station: habitable artificial satellite in low Earth orbit