Ahad's Magnitude is a theorematic formulation in astrophysics that quantifies the level of light illumination cast upon non-luminous celestial bodies by the light of the surrounding universe. It originates from a March 2004 astronomical paper by Abdul Ahad headed The Music of the Night Sky, a transcript of which was published as a letter to the editor in the Journal of the British Astronomical Association in October 2005 He asked these simple questions: "If we exclude all light coming directly and indirectly from the nearby Sun, how much illumination do the far away stars cast upon the Earth?"