P1 - The Earth and the Universe

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  • Created by: taseen11
  • Created on: 15-04-16 20:42

The Solar System

  • Star centre of solar system
  • 8 planets in solar system - spherical and have circular orbits around the sun, four closest to the sun are solid rock, the other four are gas giants
  • Each planet may have a number of moons in near-circular orbit around it
  • Asteroids are irregular lumps of rock found in circular orbit between Mars and Jupiter
  • Comets are small objects made of rock and ice with elongated orbits around the sun
  • Dwarf planets such as pluto are small spherical lumps of rock in orbit around the sun
  • 99% of solar system mass is the sun
  • Jupiter is the heaviest planet, followed by Saturn, Uranus, Neptune, Earth, Benus, Mars and Mercury
  • Neptune has the largest orbit, followed by Uranus, Saturn, Jupiter, Mars, Earth, Venus and Mercury
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The Universe: distances and sizes

  • Sun - one of thousands of millions of stars in the Milky way
  • Milky way- one of thousands of millions of galaxies which make up the universe
  • Lightyear - Used to measure distances outside of SolSys - Distance that light travels in a year. One lgiht year is 9.5 million million Kilometres
  • Speed of light - 3.0 x 10^5
  • Light takes long to reach us so we can only observe what stars were like in the past when the light left them
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Finding out about the distance to stars

  • All info we have on stars comes from radiation
  • Two stars which have the same real brightness (appear to have the same brightness) can have different relative brightness. The star which is further away has a smaller relative brightness.
  • If you know the distnace to one of the stars, the difference in their relative brightness can be used to calculate the distance to other one
  • There are some flaws with this method
    - Assumes that similar types of stars have the same real brightness
    - Based on estimating the distance to one of the stars
    - Dust, rain, clouds and light pollution can obscure readings at night
  • Telescopes in space aren't affected by distortions from Earth
  • Paralax effect - As earth orbits the sun, nearby stars moe slightly against the fixed background of distance stars - Used to find distance of a star
  • Only close stars have a suitable paralax effect for measurement
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Fusion of elements in stars

  • Sun's energy come from hydrogen. NUCLEAR FUSION - Hydrogen nuclei are jammed together so hard that they combine in pairs to form the element helium - Lots of energy released.
  • Other elements are also created - Spread through space when a star explodes at the end of its life.
  • Nuclear fusion can only be achieved with high densitiy and high temp
  • Higher densities - fusion can make heavier elements up to Iron.
  • Heavy stars explode as SUPERNOVAS, elements heavier than Iron are made during this time
  • Solar sustem made from a gas cloud about 5000 million years ago
  • Apart from hydrogen, all of the material in that cloud came from the explosions of large stars. Evidence for this comes from elements in the sun other than hydrogen and helium.


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The Expanding Universe

  • Most of the galaxies appear to be moving away from us
  • This motion of the galaxies increases the wavelength of the light we recieve from them
  • Redshift - Increase of wavelength from a galaxy moving away
  • Normally, the amount of redshift increases with distance from Earth
    - The futher away from Earth a galaxy is, the fast it is moving away from us
  • The redshift in the light coming from distant galaxies provides evidence that all parts of the Universe are expanding, with galaxies moving from each other as time goes on.

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The Big Bang

  • The universe started expanding from a single point 14000 million years ago
  • Sun created 5000 million years ago
  • Earth created 4500 million years ago
  • Detection of cosmic background radiation is evidence for this
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The future

  • Fate of the universe depeonds on its expansion. If there is sufficient mass in the universe, gravity will slow down the expansion and make it collapse again
  • The fate of the Universe difficult to predict because:
    - We can only measure mass in parts of universe which emit radiation
  • - Exact measurements of the speed and distance of galaxies is difficult because their radiation tevels such a long way to get to us
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The changing Earth: erosion and sedimentation

  • Surface of earth is always changing
  • Material erodes from mountains over time and becomes sediments which makes rocks
  • Volcanoes erupt quickly, releasing lava to make new mountains/craters
  • Sometimes plants and animals are buried by sediments or lava to become fossils
  • Slow movements of the curst can make fold rocks and new mountains
  • Rocks are eroded by moving water, glaciers, wind and rockfalls. Valleys made deeper and Mt.s made smaller and smoother by erosion.
  • Eroded rock fragments are transported by the wind, water and ice, broken up further and deposited on riverbeds and inthe sea - Sedimentation
  • Layers of this rock are crused together to form sedimentary rock
  • The age of the earth can be estimated by the age of the rock (4000m years)
  • If rocks weren't created, erosion would have worn away all of the continents to sea level.
  • Breaks in the earths crust allow moslten rock to escape from volcanoes and create new mountains.
  • Collisions between different parts of the curst also push rocks up to make new mountains
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Continental drift

  • Alfred Wegener suggested continental drift in 1915 - Continents were joined as one mass called Pangea and have moved apart since then
  • Based on
    - Continents fit together like a jigsaw puzzle
    - Similar fossals and rocks are found on continents now seperated by oceans.
  • Collisions between moving continents also explains the folding of rocks into mountains
  • Rejected because:
    - There were other simpler theories which explained his observations
    - No mechanism behind the movement of the plates
    - He was a Metrologist not a Geologist
  • Continents move because of convection currents in the mantle
  • Seafloor spreading - seafloor between continents moving apart
  • Ocean ridges - form when liquid rock fills the gap then seafloor spreading occurs
  • Solidifying rock is magnetised by the Earth's magnetic field
  • The magnetic field flips over millions of years
  • This means that the field lines in the rock also filp
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Tectonic plates

  • Tectonic plates float on semi-solid rocks
  • Tectonic plates meet at a plate boundary - earthquakes, volcanoes and mountains are found here.
  • Volcanoes occur when liquid magma is force 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 the releases of energy from tectonic plates sliding past each other
  • The rock cycle can be explained by the movment of tectonic plates
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The structure of the Earth

  • Core is liquid Iron
  • Semi-liquid rock in the mantle floats on the core
  • Outer core is a layer of liquid nickel and Iron about 2200km thick
  • The inner core is solid nickel and iron about 1250km thick
  • A thin layer of solid rock in the crust floats on the mantle
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Seismic waves

  • P-waves - move through solid crust and liquid core
  • S-waves - only move slowly through solid crust
  • Seismometers on the Earth's surface record these waves after an earthquake
  • Structure of earth can be found by measuring the time arrival of waves accross the Earth from an earthquake
  • In dense regions, waves speed up and change directions
  • P-waves longitudinal so travel along
  • S-waves transverse so traval at right angles to montion of wave
  • Core of earth must be liquid as only P-waves pass through it
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Finding out about waves

  • Amplitude - maximum height of disturbance from the undisturbed position
  • Wavelength - distance from one max disturbance to the next
  • Frequency of a wave is the number of vibrations of the source in one second
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Oscilloscope's and wave freq and speed

  • Unit of frequency is hertz(Hz). 1 Hz means 1 vibration p/s
  • Waves obey this equation:
    wave speed (m/s) = freq (Hz) x wavelength (m)
  • The higher the frequency, the shorter the wavelength.
  • The wavelength is always inversely proporitonal to the frequency
    wave speed (m/s) = distance travelled (cm) / time taken (s)
  • An oscilloscope is a machine that displays waves on a screen. A grind on the screen lets you compare the wavelength and amplitudes of waves:
    - A sound is louder if it has a larger amplitude
    - A sound is hgiher pitched if it has a shorter wavelength
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