Alexander Calder, (1898 - 1976) known to many as ‘Sandy’, was an American sculptor from Pennsylvania. He was the son of well-known sculptor Alexander Stirling Calder, and his grandfather and mother were also successful artists. Alexander Calder is known for inventing wire sculptures and the mobile, a type of kinetic art which relied on careful weighting to achieve balance and suspension in the air. Initially Calder used motors to make his works move, but soon abandoned this method and began using air currents alone.