Redshift and the Universe
Designed by Dr T. Marlow
a) If a wave source is moving relative to an observer there will be a change in the observed wavelength and frequency. This is known as the Doppler effect.
b) There is an observed increase in the wavelength of light from most distant galaxies. The further away the galaxies are, the faster they are moving, and the bigger the observed increase in wavelength. This effect is called red-shift.
c) How the observed red-shift provides evidence that the universe is expanding and supports the ‘Big Bang’ theory (that the universe began from a very small initial point).
d) Cosmic microwave background radiation (CMBR) is a form of electromagnetic radiation filling the universe. It comes from radiation that was present shortly after the beginning of the universe.
e) The ‘Big Bang’ theory is currently the only theory that can explain the existence of CMBR.
The diagram above shows a source travelling at the same speed as the waves is emitting. This produces a sonic boom effect.
Below is a diagram which shows a source travelling faster than the waves it emits.
Look at the animation below to see the waves spreading out evenly from a stationary source:
If the source is moving then the waves bunch up infront of the source, and this reduces the wavelength of the observed wave in front of the source. Similarly, the wavelength of the wavs emitted in the opposite direction to the source motion are observed to be longer than expected.