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The Solar System

Making the Solar System

  • Planets are smaller than stars & much closer
  • Clouds started to get squeezed
  • Particles close, gravity pulled things togehter, cloud collapsed
  • At the centre particles formed a protostar
  • Hydrogen nuceli joined to make helium (fusion) when temp v high
  • Fusion gives out a lot of heat & light, made the Sun
  • Material containing helium, hydrogen & heavier elements clumped to form planets

Asteriods & Comets

  • Made of stuff left over from the making of the Solar System
  • Asteroids = lumps of rock
  • Comets = balls of rock, dust & ice that orbit in boomerang
  • As the comet reaches the sun, ice melts forming a tail


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Beyond the Solar System

Milky Way Galaxy

  • Galaxy = thousands of millions of stars, Universe = thousands of millions of galaxies
  • Sun is about half way on one of the sprial arms of the Milky Way

Space Distance

  • Light year = distance that the light travels through a vacuum in one year
  • Light years are distance not time

Relative Sizes, Distances & Ages

  • Small - large = diameter of : Earth, Sun, Earth's orbit, Solar System
  • Small - large = distance  of : Sun to nearst star, Milky Way, Milky Way to nearest galaxy
  • Milky Way's diameter 600 billion x bigger than Sun's diameter about 100x bigger than Earth's
  • Age of (millions years) : Earth = 5000, Sun = 5000, Universe = 14000
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Looking into Space

Measuring Distance of Stars

  • EM shows a star's colour (temperature) 
  • Parallax = when something appears to move when you look at it from different places
  • Stars further away appear to move less 
  • Examining how bright a star is tells distance
  • Problems : atmosphere absorbs some before it reaches us, light pollution
  • Hubble Space Telescope in space = no problems

Stars & Galaxies

  • Radiation from the Sun that reaches us leaves 8 minutes before we actually see it
  • So, we see the Sun as it was 8 minutes ago
  • Sun = 4.2 light years away, light takes 4.2 years to get to us so we see it as it was 4.2 years ago
  • We see the North Star as it was 430 years ago
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The Life of the Universe

Red Shift

  • Red shift = galaxy moving away, wavelength of light changes & looks red
  • Seeing how much light has been red-shifted = how quickly it's moving away
  • Greater the red shift = faster it's moving away
  • More distant the galaxy = faster it moves away
  • This provides evidence that the Universe is expanding

Big Bang Theory

  • All matter & energy must have been compressed & exploded to make it expand
  • Still expanding today
  • 14 thousand million years ago
  • Difficult to know how much the expansion has slowed down
  • The more mass there is = the greater the slowing down of the Universe's expansion
  • Big Crunch = enough mass compared to how fast galaxies are moving = contraction
  • Not enough mass in universe to stop expansion = expanding forever 
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The Changing Earth

Rocks on Earth

  • Fossils provide evidence that Earth is constantly changing
  • Age of Earth can be estimated from rocks
  • Sedimentary rocks = eroded rocks settle as sediment in sea & get crushed together
  • Can be pushed onto surface or into Earth & then can be changed due to heating
  • When pushed to Earth = cycle starts again
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Wegener's Theory of Continental Drift

Observations of Wegener & Land Bridges

  • Wegener = supercontinent 300 million years ago
  • Land Bridges = land sunk or covered by sea as Earth cooled
  • Factors that supported W = fossils, interlinking coastlines, matching layers of rock
  • Scientists thought it was impossible land could moved by tidal forces & Earth's rotation
  • Wegener wasn't a geologist

Real Reason

  • Investigated Mid-Atlantic ridge in 1950s which is whole length of Atlantic
  • Magma rises through sea bed, solidifies & forms underwater mountains = evidence shows sea floor is spreading
  • Continents moving because of magnetic orientation to align themselves with Earth's magnetic field - as it cools they set in position
  • Every half million years Earth's magnetic field swaps direction & the rocks on either side of ridge have different bands showing how old they are & the movement of land
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The Structure of the Earth

Crust, Mantle & Core

  • Crust = what we live on, very thin, continental crust = forming land, oceanic crust = underwater
  • Mantle = all properties of a solid but can flow slowly by heat from core & radioactive decay in mantle which causes mantle to flow in convection currents
  • Core = centre of the Earth made of iron & nickel

Tectonic Plates

  • Crust & upper part of mantle cracked into tectonic plates
  • Convection currents causes them to move
  • Movements in mantle cause sea floor spreading
  • Move at a few cm per year
  • Earthquake = plates move suddenly, often near edges of plates
  • Volcanoes = magma produced where plates meet, magma rises to form volcano
  • Mounatins = plates crash into each other
  • These processes contribute to rock cycle - plates collide, rock gets pushed underneath
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Seismic Waves


  • When shock waves travel on the surface & inside Earth (recorded using seismographs)
  • Seismologists measure time taken for shock waves to reach each seismograph & which places on Earth don't get any shock waves

Seismic Waves

  • P-Wave = travels through solids & liquids, faster than S-Waves, longitudinal
  • S-Wave = travels through soilds, slower than P-Waves, transverse
  • Some can be reflected when reached a boundary between layers of the Earth
  • Change speed as properties of mantle & core change so they change direction (refraction)
  • Usually changes speed gradually = curved path, quick change = kinked path
  • Half way through Earth, P-Waves change direction = sudden change in properties as you go from mantle to core
  • No S-Waves in core's shadow = outer core is a liquid
  • P-Waves travel faster through middle of core = solid inner core
  • S-Waves travel through mantle = mantle is a solid but melts to form magma in 'hot spots'
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Waves - The Basics

Amplitude, Wavelength, Frequency & Speed

  • Waves = disturbances caused by a vibrating source that carry/transfer energy 
  • Amplitude = distance from rest position to the crest or trough, bigger amplitude = more energy
  • Wavelength = length of a full cycle of a wave - crest to crest
  • Frequency = number of waves produced by a source each second or number of complete waves passing a certain point per second
  • Distance wave has travelled (m) = speed (m/s) x time (s)

Transverse or Longitudinal

  • Transverse = most waves are, vibrations are 90degrees to the direction of travel of wave
  • Longitudinal = sound etc, vibrations along the same direction as the wave is travelling

Wave Speed

  • Wave speed (m/s) = frequency (Hz) x wavelength (m)
  • Speed of sound waves in air is constant, lower frequencies = longer length, higher = shorter
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