Astronomy Videos

• What is the shape of the Earth described as?


  An oblate spheroid
• Why is the Earth described as an oblate spheroid?

  Because it is slightly squashed due to centrifugal forces from rotation
• What causes the Earth to bulge out slightly?

  Centrifugal forces due to the Earth's rotation
• In what type of reference frame can centrifugal forces be measured?

  In a non-inertial reference frame
• What is the mean diameter of the Earth?

  13,000 kilometers
• What are the layers of the Earth from the surface to the center?

  • Crust
  • Mantle
  • Outer core (liquid)
  • Inner core (solid)
• How thick is the Earth's crust under the oceans?

  About 5 to 10 kilometers thick
• What is the state of the mantle beneath the Earth's crust?


  It is mostly solid but behaves like a viscous liquid over geological time scales
• What causes the Earth's magnetic field?

  Convection currents in the liquid outer core
• Why does the inner core remain solid despite high temperatures?

  Due to the immense pressure from the outer core, mantle, crust, and atmosphere
• How do scientists learn about the Earth's interior?

  By analyzing acoustic waves that pass through the Earth
• What is the coordinate system used to refer to points on the Earth's surface?

  • Latitude: North-South position
  • Longitude: East-West position
• What is the latitude at the equator?

  0 degrees
• How are longitude lines oriented?

  They run from the North Pole to the South Pole
• What is the special name for the longitude line that passes through Greenwich?

  The prime meridian
• What are the Tropic of Cancer and Tropic of Capricorn?

  Latitude lines at approximately 23 degrees north and south where the sun is directly overhead at certain times of the year
• What is the celestial equator?

  The imaginary line in the sky directly above the Earth's equator
• What is Rayleigh scattering?

  The scattering of light that causes the sky to appear blue
• Why do stars appear to twinkle?

  Due to atmospheric turbulence affecting the light path
• What is dark adapted vision?

  The increased sensitivity of the eyes to low light levels after being in the dark
• How can one preserve dark adapted vision while observing stars?

  By using a red light source
• What is the effect of light pollution on star observations?

  It makes it difficult to see stars due to scattered light
• What happens to the visibility of stars when the sky is dark?

  Stars become more visible due to higher contrast
• What is averted vision?

  Looking slightly away from a faint star to see it better in peripheral vision
• What are the main points covered in the first topic of the NXL GCSE in Astronomy?

  • Shape of the Earth (oblate spheroid)
  • Earth's layers (crust, mantle, outer core, inner core)
  • Coordinate system (latitude and longitude)
  • Effects of Earth's atmosphere on observations