karaites: a Jewish sect that recognizes only the Hebrew Scriptures as the source of divinely inspired legislation and denies the authority of the postbiblical tradition of the Talmud; the sect arose in Iraq in the eighth century
entity: that which is perceived or known or inferred to have its own distinct existence (living or nonliving)
black-body radiation: the electromagnetic radiation that would be radiated from an ideal black body; the distribution of energy in the radiated spectrum of a black body depends only on temperature and is determined by Planck's radiation law