4.2 Formation of the Universe
The Expanding Universe and the Red Shift
In the 1920's, astronomer Edwin Hubble used the Doppler Effect to determine that the Universe is expanding. Hubble found that the light from distant galaxies was shifted towards lower frequencies, or the red end of the spectrum. This is known as a Red Doppler Shift, or a Red-shift. If the galaxies were moving towards Hubble, the light would have been blue-shifted. By analysing the spectra of distant galaxies, it has been discovered that, on average, galaxies are rushing away from our Milky Way Galaxy at thousands of kilometres per second. We know this because the spectra of these galaxies are red-shifted and the further out they are, the faster they are found to be moving. This at first seems to indicate that we may be at the centre of the Universe. However, it is thought that no matter where you are in the Universe, galaxies race away from you. Galaxies are not moving through space but space is thought to be expanding and the expansion is happening between all points in the Universe.