ABSTRACT
The Christian Doppler shift of a spectral line provides information about the motion of its source relative to the observer. The Doppler effect is important to astronomy and cosmology, therefore. In essence, Doppler's discovery is that if a source of wave is in motion relative to an observer, then the wavelength of this wave as observed by that observer must be different than that it is emitted by the source with. The Doppler shift results from only the relative motion of the source and the observer. From the Doppler shift of a source, the observer can then infer the nature of its motion. The Doppler effect is vital for astronomy, as light is the only available source of people information about astronomical objects. It therefore pays to consider the derivation of the Doppler shift in detail here. The erroneous observational results include those important to quasars, active galaxies, and cosmology.
