Astronomy - Chapter 1 - Earth, Moon and Sun - EARTH

A mind map to show facts about Earth.

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  • Created by: Georgina
  • Created on: 08-04-13 10:35
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  • Astronomy - Chapter 1 - Earth, Moon and Sun - EARTH
    • Key features
      • It's atmosphere - oxygen and nitrogen
      • Liquid water - covering 70% of the surface
      • Life in all it's diverse forms
    • Scattering Light
      • Blue light has a small wavelength compared to red light and green light
      • Molecules in the air (dust) scatter the blue light in all directions - this does not happen with red and green light
      • This is why we see a blue sky
    • Light Pollution
      • It's called SKY GLOW
      • It prevents faint stars, nebulae and the Milky Way from being observed
      • wasteful light shines up into the sky - causes an orange background haze
      • The countryside is the ideal place to observe
    • Eratosthene
      • He was the first person  to get an accurate measurement of the Earth's circumference
      • He was a Greek geographer and mathematician in the 3rd century BC
      • He put a stick at Alexandria - the angle was 7*
      • He got another stick and put it in Syene which was on the Tropic of Cancer
        • This means it casts no shadow
      • He worked out that the distance between these two places was 790 km
      • He used geometry to find out that the Earth was 50 times the value
      • His result was very accurate - 5% error
    • Earth's Shape
      • Earth is an oblate spheroid
      • This means that it is slightly flattened at the poles
        • It is squashed by 42 km at the north and south poles
      • Earth's diameter is 13,000 km
      • Earth is a spheroid because...
        • Ships disappear over the horizon
        • satellites orbit the Earth
        • the curve of the Earth's shadow during a lunar eclispe
    • Earth's rotational period
      • Earth has a rotational period of 23 hours and 56 minutes
      • To get a 24 hour day the Earth has to spin an extra 1 degree - which takes 4 minutes
    • Key terms
      • Equator: A line dividing the Earth into the Northern and Southern hemisphere
      • Tropics: Two parallel lines of latitude representing the points farthest north and south at which the sun can shine directly overhead
      • Latitude: Distance of a place either North  or South of the Earth's equator  usually expressed in degrees and minutes
      • Longitude: Angular distance on the earth's surface expressed in degrees (or hours), minutes, and seconds
      • pole: two locations North and South pole on the surface of the Earth or a celestial object
      • Horizon: The line at which the Earth surface and sky appear to meet
      • Meridian: A circle of constant longitude passing through a place on the Earth surface and the poles
      • Zenith: highest point reached by a celestial
    • Telescopes
      • Refractor - A glass convex lens collects the light and brings it into a focus
      • Reflector - A curved mirror (or one made from several segments) collects the light
      • Some of the largest telescopes are made from reflectors
        • Because: They do not suffer from chromatic aberration because all wavelengths will reflect off the mirror in the same way
        • The mirrors can be made very big
        • They are cheaper and can be made the same size as refractors
        • Light is reflecting off the object rather than passing through it
        • Only one side of the telescopes objects needs to be perfect
    • Van Allen Belts
      • Are two doughnut-shaped rings of spiralling high-energy particles held in place by Earth's magnetic field
      • The inner belt was discovered in January 1958
        • The inner belt consists of high energy protons - formed by collisions between cosmic rays and atoms in the atmosphere
        • The inner belt can pose a hazard to astronauts and scientific instruments as it has low altitude of 0.1 and 1.5 Earth-radii
      • The outer belt was discovered in December 1958
        • The outer belt is more dynamic and consists of electrons and other charged particles emitted by the sun
        • The outer belts altitude is between 3 and 10 Earth-radii
    • Earth's atmosphere
      • Benefits of Earth's atmosphere
        • Absorbs UV radiation
        • Absorbs X-rays and gamma rays
        • regulates the temperature - this allows water to remain in liquid form
        • Provides us with oxygen - so we can breathe
        • PARTLY stops meteoroids from hitting us
        • Drawbacks of Earth's atmosphere
          • Refraction of light passes through the turbulent atmosphere causing the stars to twinkle and restricting the resolution of the image
          • Selective scattering making the sky appear blue and preventing astronomers from making observations during the day
          • Absorption and reflection of radiation preventing most wavelengths from reaching sea-level
      • UV, infrared and X-rays are sited on high ground so that they can be detected
  • Life in all it's diverse forms
  • Scattering Light
    • Blue light has a small wavelength compared to red light and green light
    • Molecules in the air (dust) scatter the blue light in all directions - this does not happen with red and green light
    • This is why we see a blue sky
  • Light Pollution
    • It's called SKY GLOW
    • It prevents faint stars, nebulae and the Milky Way from being observed
    • wasteful light shines up into the sky - causes an orange background haze
    • The countryside is the ideal place to observe
  • Equator: A line dividing the Earth into the Northern and Southern hemisphere
  • Benefits of Earth's atmosphere
    • Absorbs UV radiation
    • Absorbs X-rays and gamma rays
    • regulates the temperature - this allows water to remain in liquid form
    • Provides us with oxygen - so we can breathe
    • PARTLY stops meteoroids from hitting us
    • Drawbacks of Earth's atmosphere
      • Refraction of light passes through the turbulent atmosphere causing the stars to twinkle and restricting the resolution of the image
      • Selective scattering making the sky appear blue and preventing astronomers from making observations during the day
      • Absorption and reflection of radiation preventing most wavelengths from reaching sea-level

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