More than 900,000 quasars have been found (as of July 2023), most from the Sloan Digital Sky Survey. All observed quasar spectra have redshifts between 0.056 and 7.64 (as of 2021), which means they range between 600 million and 30 billion light-years away from Earth. Because of the great distances to the farthest quasars and the finite velocity of light, they and their surrounding space appear as they existed in the very early universe.