the universe

• absorption spectra:

  when observing light from distant stars and galaxies through a spectrometer you see a pattern of black lines on the spectrum. these lines represent wavelength of light that have been absorbed by elements in the gases in the star's atmosphere. as every element will absorb different wavelengths, each element has a unique pattern of lines.

  this pattern can be used to identify which elements are present.
• this is an example of a hydrogen spectrum, only hydrogen will absorb light in that specific pattern of lines.

  
• cmbr (cosmic microwave background radiation):

  high energy gamma radiation released at the big bang has travelled through the universe since then, because the universe is expanding the wavelength of these waves has been stretched to become microwave radiation.

  as microwave radiation can be measured throughout the universe it is evidence that the universe started from a hot big bang which released a lot of energy.
• the big bang:

  both these pieces of evidence support the big bang theory which states that the universe started from one point where all the energy and matter was released.
• cosmological red shift:

  when comparing light from distant galaxies to spectra created in the laboratory scientists noticed the pattern of lines had been shifted towards the red side of the spectrum, with the longer wavelength.

  
• the wavelength has increased because the light was stretched as it travelled through space that was expanding.

  as light is stretched as it travels through expanding space, light from galaxies that are further away is stretched more as the light travels through space for longer.
• all galaxies started at the same point and the universe has expanded from that point.