Merce Cunningham, ubiquitously hailed as the greatest choreographer in the world, died Sunday night in Manhattan at the age of 90. In his younger days, the longtime New Yorker had himself been unparalleled as a dancer, and continued to perform with his company until 1989, when he was 70. But he is certainly most remembered for his long, influential career as a choreographer. Cunningham made us rethink dance again and again, bringing dance into full maturity as a major art-form. He was a lifelong collaborator and partner of John Cage, and was celebrated for having music and dance independently composed, emphasizing that dance was about movement, not music.