sound and space

• Collision theory


  1. Object of similar size to Mars (called Theia) collided with Earth

  2. Impact caused a disc of dust and rock to form around the Earth

  3. Dust and rock eventually came together under gravity to form the Moon
• Theia


  Object of similar size to Mars that collided with Earth
• Evidence that supports the collision theory

  • The Moon is less dense than the Earth
  • Samples of rock from the Moon show that its surface was once molten
  • The Moon has a small iron core, similar to the Earth
  • There is evidence outside the Solar System of similar collisions causing rings of rock and dust
  • The collision theory fits with the theory of how the Solar System was formed
  • The composition of rocks on the Earth and the Moon are the same
• Evidence that contradicts the collision theory

  • The surface of the Earth does not appear to ever have been molten. A collision that formed the Moon would have caused the surface to melt
  • Venus has no moon. Collisions in the early years of the Solar System would have been common and scientists would have expected Venus to have a moon formed in the same way
  • The composition of rocks on the Moon would be expected to be more similar to rocks on Theia than rocks on Earth. In fact, the composition of the Moon is more similar to Earth
• Amplitude


  The maximum distance that particles move either forward or backward in a sound wave
• Peak


  The top of a wave graph where the line is at its highest
• Trough


  The bottom of a wave graph where the line is at its lowest
• As the amplitude of a sound wave increases


  The loudness of the wave increases
• As the frequency of a sound increases

  The pitch increases
• Interference of sound


  • Waves have the same frequency and same amplitude
  • Reinforce
  • Cancel
• Waves that reinforce


  1. Sound waves reinforce when they meet peak to peak/trough to trough

  2. Amplitude of the sound waves is added together

  3. Frequency doesn't change
• Application (loudspeaker in stages)

  • The curved lines in the diagram represent peaks in the sound waves. Where two of these lines cross, the waves will reinforce. A person at that position will hear a louder sound.
• Waves that cancel


  1. Sound waves cancel when they meet peak to trough

  2. Amplitude of the two waves becomes zero
• Application (noise cancelling headphones)


  • The headphones create a sound wave that will cancel with the sound wave from the surroundings
• Nebula


  A cloud of gas and dust, (gases in nebula are mostly hydrogen and small quantity of helium)
• Stellar nursery


  A place in the nebula where stars are formed
• How stars are formed

  1. In a stellar nursery, the mass of dust and gas collects together by gravity, and becomes larger

  2. As the force of gravity increases, pressure inside the star gets very large

  3. Large pressure causes reactions that give out light and form stars
• Tectonic plates


  Parts of the Earth's crust that can move in the mantle
• Evidence for tectonic plates

  • The jigsaw model: The shapes of the continents fit together because they were one large continent
  • The fossil record: Same fossils of the same species are found in different continents where they fit together
  • The alignment of magnetic materials in rocks: Newly formed rocks and old rocks in the mid-ocean ridges show symmetrical opposing patterns/different patterns
• Pangaea


  • 225 million years ago
• Laurasia


  • 150 million years ago
• Convection current that move the plates

  Mantel is heated by the core, the fluid in the mantle expands when heated and becomes less dense and arises towards the crust so it cools and sinks again resulting in a convection current