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The Solar System

  • the centre of our Solar System is the sun
  • the 8 plants in the solar system have nearly circular orbits around the Sun
  • the four planets closest to the sun are solid rock
  • the four outer plants are gas
  • asteroids are lumps of rock, with near circulated orbits between Mars and Jupiter
  • comets are small objects made of rock and ice with very elongated orbits around the Sun
  • Dwarf Planets such as pluto are small lumps of rock in orbit around the Sun
  • 99% of the Solar Systems mass is the sun
  • Planet order from the sun- The sun, mercury, venus, earth, mars, jupiter, saturn, uranus, neptune
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  • The sun is one of the thousands of stars in the Milky Way
  • the Milky Way is one of the thousands of Galaxies which make up the universe
  • distances to objects outside the solar system are measured in light years
  • a light year is the distance that light travels in a year
  • one light year is 9.5 million kilometres
  • the speed of light= 300,000km/s
  • two stars that have the same real brightness, can have different relative brightness, the star which is further away has a smaller relative brightness
  • if you know the distance to one of the stars, the difference in their relative brightness can be used to calculate the distance to the other one
  • this method is difficult due to light pollution, rain, and clouds
  • as the Earth orbits the Sun, nearby stars move slightly against the fixed background of distant stars, this is called Parallax effect
  • only nearby stars have a parallax effect which is large enough to be measured
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Fusion of elements in Stars

  • the suns energy comes from hydrogen
  • hydrogen nuclei are jammed together and combine in pairs to form the element helium
  • this is called nuclear fusion
  • nuclear fusion is only possible when there are very high densities and temperatures
  • heavy stars end their lives as supernova, this is a big explosion where all the different chemical elements are made
  • the solar system was made from a collapsing cloud of dust and gas about 5000 million years ago
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The Expanding Universe

  • most of the galaxies appear to be moving away
  • the motion of the galaxies increases the wavelength of the light we recieve from them
  • the increase of wavelength from a galaxy moving away is called redshift
  • the redshift in the light coming from distant galaxies provides evidence that all parts of the Universe are expanding with galaxies moving apart from eachother as time goes on
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The Big Bang Theory

  • The Universe started expanding rapidly from a single point about 14,000 million years ago
  • the sun was created about 5000 million years ago
  • the earth was created about 4500 million years ago
  • Scientists believe that the Earth was created with a 'big bang'
  • the theory states that 13.7 billion years ago all the matter in the Universe was concentrated into a single incredibly tiny point
  • this began to enlarge rapidly in a hot explosion and is still expanding today
  • the theory is supported by red shift
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Erosion and Sedimentation

  • material erodes slowly from mountains and becomes sediments
  • volcanoes erupt quickly spewing out lava to make new mountains or a crater
  • Geologists study rocks for evidence as to how the Earth has changed
  • eroded rock fragments are transported by the wind, water, and ice, and deposited on river beds and in the sea, this is called sedimentation
  • breaks in the Earths crust allow molten rock to escape from volcanoes and create new mountains
  • collisions between different parts of the crust also push rocks up to make new mountains
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Continental Drift

  • Alfred Wegeners theory of continental drift says that millions of years ago there was a single land mass on Earth, since then it has split into several continents due to drifting apart
  • Wegeners theory was based on the following evidence; the way continents fit together so well, similar fossils and rocks are found on continents now seperated by oceans
  • geologists didnt accept Wegeners theory because they already had simpler theories, and Wegener was not a trained geologist
  • continents move because they sit on the mantle, whose rocks slowly move by convection as they carry heat away from the Earths core
  • the seafloor between continents moving apart can increase by a few centimetres each year (seafloor spreading)
  • Oceanic ridges form on the expanding seafloor where liquid rock from the mantle fills the gap
  • the solidifying rock in oceanic ridges is magnetised by the Earths field
  • The Earths magnetic field changes direction over millions of years
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Tectonic Plates

  • Tectonic plates meet at a plate boundary, earthquakes volcanoes and mountains are found here
  • volcanoes occur when liquid magma is forced through cracks where tectonic plates are moving apart
  • volcanic mountains form when one tectonic plate is forced under another heading towards it
  • fold mountains form when two tectonic plates meet head on
  • earthquakes are releases of energy from tectonic plates sliding past eachother
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Seismic Waves

  • P-waves; move quickly through solid crust and liquid core
  • S-waves;move slowly through the solid crust
  • seismometers record these waves after an Earthquake
  • we can work out the structure of the Earth by measuring the time of arrival of seismic waves across the Earth from an Earthquake
  • P waves are longitudinal so the particles vibrate along the direction of motion of the wave
  • S-waves are transverse, so the particles vibrate at right angles to the direction of motion of the wave
  • the core of the Earth must be liquid because only P waves pass through it 
  • a wave transfers energy away from a vibrating source, creating a series of disturbances as it moves
  • the amplitude of a wave is the maximum height of the disturbance from the undisturbed position
  • the wavelength is the distance from one maximum disturbance to the next
  • the frequency of a wave is the number of vibrations of the source in one second 
  • the unit of frequency is hertz (Hz) 1Hz means 1 vibration per second
  • waves= wave speed(m/s)= frequencyXwavelength
  • the higher the frequency the shorter the wavelength, the wavelength is always inversely proportional to the frequency
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