Pittsburgh Ballet Theatre presents, as the centerpiece of its 40th anniversary season, "Light/The Holocaust & Humanity Project," a work that demonstrates how ballet can transcend its art form to become an agent of change, at 8 p.m. Friday, at 2 and 8 p.m. Saturday, and at 2 p.m. Sunday at the Byham Theater, 101 Sixth St. Tickets range from $20.50 to $88.50 and are available by calling 412-456-6666 or visiting the Web site, www.pbt.org.