Astronomy paper 1 topic 1

• Shape of the Earth

  Oblate spheroid - spherical but slightly squashed due to centrifugal forces from rotation
• Earth's diameter is approximately 13,000 km
• Earth's internal structure


  • Crust
  • Mantle
  • Outer core
  • Inner core
• Tectonic plates


  Plates that the Earth's crust is split into, floating on the mantle
• Latitude


  Measurement of north-south position on Earth's surface
• Longitude


  Measurement of east-west position on Earth's surface
• Special latitude lines


  • Tropic of Cancer
  • Tropic of Capricorn
• Prime meridian


  Longitude line passing through Greenwich, UK, defining 0 degrees longitude
• Geographic poles


  North and south poles, axis of Earth's rotation
• Magnetic poles


  North and south poles of Earth's magnetic field, different from geographic poles
• Earth's axis is tilted 23 degrees relative to its orbit around the Sun
• Celestial poles


  Points in the sky corresponding to the geographic north and south poles
• Celestial equator


  Imaginary line in the sky corresponding to the Earth's geographic equator
• Ecliptic


  Plane of Earth's orbit around the Sun
• Atmosphere


  • Absorbs electromagnetic radiation
  • Scatters blue light (Rayleigh scattering)
  • Causes twinkling of stars
• Observing the night sky is better with dark-adapted vision and using red light sources