German painter, sculptor, and Kinetic artist, born in Laasphe, Westphalia. At the age of sixteen he was called up for war service as an anti-aircraft gunner and was taken prisoner. After the war he trained at the academies of Munich and Düsseldorf, 1948–53, and then studied philosophy at Cologne University, 1953–7. With Heinz Mack and Günther Uecker he founded the Zero group in 1957. His work has included paintings employing smoke and large out-of-doors light projects such as Lichtlinie at the Massachusetts Institute of Technology in 1968. In 1969 he coined the term Sky art to refer to certain works of this type. He has had a great influence as a teacher and from 1974 to 1994 was director of the MIT Center for Advanced Visual Studies (CAVS) which specializes in links between art and technology.