Red-Shift and the Big Bang

The universe seems to be expanding

As big as the universe already is, it looks like it’s getting even bigger. All it galaxies seem to be moving away from each other. There’s good evidence for this.

  • When we look at light from most distant galaxies, we find that the wavelength has increased
  • The wavelengths are all longer than they should be-they are shifted towards the red end of the spectrum.   * This is called red shift.
  • This suggest the source of the light is moving away from us.
  • Measurements of the red-shift indicate that these distance galaxies are moving away from us(receding) very quickly-and it’s the same result whichever direction you look in.
  • More distant galaxies have greater red shifts than nearer ones. This means that more distant galaxies are moving away faster than nearer ones.
  • The inescapable conclusion appears to be that the whole universe (space itself) is expanding.

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This evidence suggests the universe started with a bang

So all the galaxies are moving from each other at great speed-suggesting something must have got them going. That ‘something’ was probably a big explosion-the Big Bang. Here’s the theory:

  • Initially, all the matter in the universe occupied a very small space. This tiny space was very dense and so was very hot.
  • Then it ‘exploded’-space started expanding, and the expansion is still going on.

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New evidence might change out theories·

Something important to remember is that the Big Band theory is the best guess we have so far. Whenever scientists discover new evidence, they must either make a new theory or change a current one to explain what they have observed

  • There are still lots we do not know about the universe.
  • Observation of supernovas from 1998 to the present day appear to show the distant galaxies are moving away from us faster and faster.
  • Currently, scientists think the universe is mostly made up of dark matter and dark energy. Dark matter is the name given to an unknown substans which holds galaxies together but does not emit any electromagnetic radiation.
  • Dark energy is thought to be responsible for the accelerated expansion of the universe. But no-one knows what these things are, so there are lots of different theories about it.
  • These theories get tested and are either accepted or rejected.

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