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- Created by: Elliemcgowanx
- Created on: 03-05-14 11:40
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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Distances
- 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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