space physics

• Questions about where we are, and where we came from, have been asked for thousands of years
• In the past century, astronomers and astrophysicists have made remarkable progress in understanding the scale and structure of the universe, its evolution and ours
• New questions have emerged recently about 'dark matter' and what is causing the universe to expand ever faster
• Dark matter


  Bends light and holds galaxies together but does not emit electromagnetic radiation
• Components of our solar system

  • One star (the Sun)
  • Eight planets
  • Dwarf planets
  • Natural satellites (moons)
• Our solar system is a small part of the Milky Way galaxy
• Formation of the Sun

  1. Dust and gas (nebula) pulled together by gravitational attraction

  2. Fusion reactions start
• Fusion reactions in stars

  Lead to an equilibrium between the gravitational collapse of a star and the expansion of a star due to fusion energy
• Life cycle of a star

  • Determined by the size of the star
  • Fusion processes produce all naturally occurring elements
  • Elements heavier than iron are produced in a supernova
• The explosion of a massive star (supernova) distributes the elements throughout the universe
• Fusion processes in stars

  Lead to the formation of new elements
• Gravity


  Provides the force that allows planets and satellites (both natural and artificial) to maintain their circular orbits
• For circular orbits, the force of gravity


  Can lead to changing velocity but unchanged speed
• For a stable orbit, the radius


  Must change if the speed changes
• Red-shift


  Observed increase in the wavelength of light from most distant galaxies
• The further away the galaxies


  The faster they are moving and the bigger the observed increase in wavelength
• The observed red-shift provides evidence that space itself (the universe) is expanding and supports the Big Bang theory
• Big Bang theory


  Suggests that the universe began from a very small region that was extremely hot and dense
• Since 1998 onwards, observations of supernovae suggest that distant galaxies are receding ever faster
• Explaining red-shift


  1. Qualitatively the red-shift of light from galaxies that are receding

  2. The change of each galaxy's speed with distance is evidence of an expanding universe

  3. How red-shift provides evidence for the Big Bang model

  4. How scientists are able to use observations to arrive at theories such as the Big Bang theory
• There is still much about the universe that is not understood, for example dark mass and dark energy