Just when you thought you'd figured out what art really is, Levitated Mass by Michael Heizer is where modern art and the Protestant work ethic weirdly intersect, which is to say that a 340-ton granite megalith painstakingly transported over two weeks from Riverside sits in a 456-foot-long slot, and you get to contemplate it all. Clearly, your kid couldn't do that. Forty-five years in the making -- from concept to construction to carefully avoided clusterfuck -- it's whatever you want it to be. Process art? Yes. Land art? Yes. Cubism? Well, yes, depending on where you're standing when you look at it. The exhibition is dedicated to the memory of philanthropist and children's activist Nancy Daly, which makes perfect sense given the fact that many creative discoveries come from children playing with rocks. LACMA, Resnick North Lawn, 5905 Wilshire Blvd., L.A. (323) 857-6151, lacma.org.