redshift:Redshift is the phenomenon where light or other electromagnetic radiation from an object moves towards longer wavelengths, indicating that it is moving away from the observer.
Doppler Effect:The change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source.
spectral line:A dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light at a specific wavelength by a substance.