P1 REVISION!!

Created by: Avani.Shanbhag27
Created on: 22-06-15 18:11

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P1-The Earth and the Universe
- Beyond Solar System
  - Milky way galaxy, sun is in middle of one of the spiral arms of the galaxy
  - Every galaxy is made up of thousands of millions of stars
  - The Universe has more than a thousand million galaxies
  - Distance in space is measured in light years
  - Age of stuff in space
    - Earth: 5000 million years
    - Sun: 5000 million years
    - Universe: 14000 million years
- Looking in Space
  - Stars
    - Emit electromagnetic radiation
    - Measuring distance 'how far away they are'
      - Parallax
      - Brightness emitted (not as reliable)
  - problems to see things in space
    - Earth's atmosphere
    - Light Pollution
  - Stars are never seen in the present, e.g. the sun radiation reaches us in 8 minutes so whatever happens to the sun now will happen to us in 8 minutes
- Life of the Universe
  - It's expanding
    - Red Shift . further = redder light = faster
    - Big Bang Theory. There must be a force pushing the universe away from it's core. (stretching it)
  - Will it end one day?
    - Ultmate fate relies on how fast it's expanding and the total mass in it
      - Not always accurate results.
      - Hard to measure
      - More mass = greater gravitational pull = slower expansion of universe - ending with a big crunch
      - Less mass = eternal expansion of universe
- Changing Earth
  - The Earth is always changing, in a few million years the Earth map will be very different as the continents would have all moved
  - Proof that Eearth has been changing and will continue.
    - e.g. Colorado River has eroded the rock of the Grand Canyon leaving a woven valley shape through Arizona
    - Cliffs are worn off by seas. We can see this ourselves
    - Lava from volcanic eruptions forms new rock when it cools.
    - Fossils show that new rock is always forming.
      - Lava from volcanic eruptions forms new rock when it cools.
    - Layer of Rock , older = lower layer
    - Rock Cycle
      - Particles eroded = sedimentary
        Heat, pressure from core change crystal allignment = metamorphic
      - Melted, cools slow or quick = igneous rock
        Instrusive (inside)
        
        Extrusive (outside)
      - Some rocks can be folded
- Continental Drift - Wegener's theory
  - His Evidence for theory
    - Coastlines of Africa and South America seemed to fit together
    - Glacier scratches in modern day 'hot' countries with forests
    - Fossils of similar animals found on different sides of Earth
  - Why Rejected
    - He wasn't even a geologist
    - He didn't know how the continents could have moved.
  - Why accepted
    - When: During World War 2
    - Sea Floor Spreading
      - Iron, magnetic stripes were detected on the ocean bed.
        Every half million years the Earth's magnetic field swaps so there are zig zag shaped stripes
  - Pangaea -Supercontinent
- The Earth's structure
  - Crust
    - Continental - forms land
    - Oceanic - under oceans
  - Mantle
    - Has all properties of solid but can flow slowly. Made up of Molten Rock
  - Core
    - This heats the mantle and causes the magma to flow in convection currents.
    - Thought to be made up of mainly iron and nickel.
  - Tectonic Plates - USE YOUR GEOGRAPHY
- Seismic Waves
  - Earthquakes produce wave motions (shock waves) that travel on the surface and inside the Earth.
  - Measured using SEISMOGRAPHS by SEISMOLOGISTS, who measure how long the waves take to travel
  - P Waves
    - Travel through solids and liquids
    - Longtitudinal
    - Have a sudden change in properties as u go from the mantle to core.
    - Seem to travel faster through middle of core suggesting that inner core= solid.
  - When the waves reach a boundary between different layers of Erth some will be reflected.
  - When properties (e.g. density) of the mantle or core change the waves change speed and direction, which is refraction.
    - If they change too quickly, it can result in a curved path
- Waves
  - They all have:
    - Amplitude (distance from the rest position to the crest or trough
    - Wavelength (length of the full cycle of the wave)
      - When the speed is constant, the wavelength is inversely proportianal to the frequency.
        Frequency (the number of complete waves passing a certain point per second OR the number of waves produced by a source per second
      - Waves with lower frequencies have longer wavelengths and those with higher frequencies have lower wavelengths.
        Frequency (the number of complete waves passing a certain point per second OR the number of waves produced by a source per second
    - Speed (SPEED)
      - When the speed is constant, the wavelength is inversely proportianal to the frequency.
  - Transverse
    - e.g. light, other EM waves, S waves
    - The vibrations are at 90 degrees to the wave's direction of travel
  - Longitudinal
    - e.g. sound, ultrasound, P waves
    - The vibrations are at the same direction.
  - Wave speed (m/s) = Frequency (Hz) x Wavelength (m)
  - distance (m) = speed (m/s) x time (s)
  - Carry and transfer energy in the wave travel direction, DON'T TRANSFER MATTER
  - Disturbances caused by a vibrating source.
- The Solar System
  - There are 8 planets orbiting the sun in elipses (circular paths)
    - Closest to Sun:Mercury, Venus, Earth and Mars
    - Furthest from Sun: Jupiter, Saturn, Uranus and Neptune
    - Asteroid belt in middle of inner and outer planets
  - Moons orbit planets
  - Planets only reflect light whereas stars give out lights so you can see them even though they are very far away
  - Formation
    - Big clouds of dust and gas collapsed in on themselves due to gravity
      - Fusion took place when the temperature got high and particles joined to form a protostar
        Fusion: Hydrogen nuclei joined together to make helium
        
        Fusion gives out lots of heat and light thus a star, the sun, was born
        Fusion: Hydrogen nuclei joined together to make helium
    - Around the sun, material from cloud containing hydrogen, helium etc. started to clump together, forming planets
    - Left over material = asteroids and comets
      - Comets = rock, dust and ice. Orbit sun in elongated elipses
      - Asteroids = rubble of rock between Mars and Jupiter

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P1 REVISION!!

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