Topic 1 - Planet Earth

• What shape is the earth?

  Oblate spheroid
• What is the mean diameter of the Earth?

  13,000 km
• What does an oblate spheroid mean?

  Flattened at the poles, and bulges at the equator.
• How far south or north a position is.

  Latitude
• How far east or west a position is.

  Longitude
• What has a longitude of 0 degrees?

  The prime meridian
• What has a latitude of 0 degrees?

  The Equator
• What has a latitude of 23.5 degrees north?

  Tropic of Cancer
• What has a latitude of 23.5 degrees south?

  Tropic of Capricorn
• What is the zenith?


  A point directly above the observer's head
• How can an observer in on Earth find their latitude?

  altitude of NCP (or SCP) = observer's latitude
• What is the latitude of the north pole?

  90 degrees north
• What is the latitude of the south pole?

  90 degrees south
• What has a latitude of 66.5 degrees north?

  Arctic Circle
• What is the latitude of the Antarctic circle?

  66.5 degrees South
• What are circumpolar stars?

  Stars which do not set as viewed from a given latitude
• When will as star be circumpolar ?


  If the polar distance is less than the latitude of the observer.
• What day is the summer solstice?

  June 21st
• What is on the 23rd September?

  Autumnal Equinox
• What day is the winter solstice?

  December 21st
• What is on the 21st March?

  Vernal equinox
• When is the sun directly over the equator?

  on the two equinoxes
• What are the 4 main divisions of the earth?

  crust

  mantle

  outer core

  inner core
• Why does the sky appear blue?

  Blue light is scattered more than other colours because it travels as shorter waves.
• Why do stars twinkle?

  Light refracts at different amounts due to different densities in the earths atmosphere
• Do starts twinkle more as they get closer to the horizon?

  yes
• What causes light pollution?

  outdoor lights that emits light upwards
• What causes tides on earth?

  Gravitational pull of the moon (and sun)
• What did Eratosthenes do?

  Calculated the circumference of the Earth.
• What did Aristarchus do?

  Heliocentrism
• What shape is the earths orbit around the sun?

  elliptical
• What is perihelion?


  Closest point to the sun in the earths orbit.
• What is the point in the earths orbit when it is farthest away from the sun?

  Aphelion
• What is an astronomical unit (AU)?

  The average distance between the Earth and the Sun.
• What is 1 AU in km?

  roughly 150,000,000 km