WordNet (r) 3.0 (2006):

John Tyndall
    n 1: British physicist (born in Ireland) remembered for his
         experiments on the transparency of gases and the absorption
         of radiant heat by gases and the transmission of sound
         through the atmosphere; he was the first person to explain
         why the daylight sky is blue (1820-1893) [syn: Tyndall,
         John Tyndall]