Redshift (z)
Redshift (z) : A unit of relative distance used in astronomy. The universe is expanding, so distant galaxies are receding from the earth. The faster the speed of recession, the farther the object. Just as sound from a receding train is lowered in pitch, light from distant galaxies is shifted toward longer wavelengths, that is, toward the red end of the spectrum. The redshift equals z if the wavelength of light is z + 1 times the normal wavelength; thus a redshift of 0.40 means that the wavelength of the light is 40% longer than normal. Using the Hubble space telescope, astronomers have measured redshifts greater than 5.0
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