Arp originally proposed his theories in the 1960s, however, telescopes and astronomical instrumentation have advanced greatly; the Hubble Space Telescope was launched, multiple 8-10 meter telescopes (such as those at Keck Observatory) have become operational, and detectors such as CCDs are now more widely employed. These new telescopes and new instrumentation have been utilized to examine QSOs further. QSOs are now generally accepted to be very distant galaxies with high redshifts. Moreover, many imaging surveys, most notably the Hubble Deep Field, have found many high-redshift objects that are not QSOs but that appear to be normal galaxies like those found nearby. Moreover, the spectra of the high-redshift galaxies, as seen from X-ray to radio wavelengths, match the spectra of nearby galaxies (particularly galaxies with high levels of star formation activity but also galaxies with normal or extinguished star formation activity) when corrected for redshift effects.