redshift

noun Astronomy.

1. a shift toward longer wavelengths of the spectral lines emitted by a celestial object that is caused by the object moving away from the earth.

noun

1. a shift in the lines of the spectrum of an astronomical object towards a longer wavelength (the red end of an optical spectrum), relative to the wavelength of these lines in the terrestrial spectrum, usually as a result of the Doppler effect caused by the recession of the objectCompare: blueshift