Can you judge a female diva based on how she copes with middle age? Cher has managed several fascinating career reinventions, but generally female artists fare no better than their male peers (e.g., the unseemly evolution from Casanova front man to potbellied leather pants-wearer). Thirty-seven-year-old Mariah Carey has struggled to reconcile herself with hip-hop; Whitney Houston seems unlikely to star again in anything other than TV reality shows; Diana Ross strikes me as more desperate for a resurgence than Neil Diamond. Using artists like these as standard-bearers, it's easy to see why Björk at 41 is cooler, more confident and far more compelling than any of her peers. You don't even have to listen to her new album, Volta. (And based on the mixed reviews it's received, that might be a good idea.) Divas are defined as much by what you see as what you hear; just compare Björk's public image to that of, say, Sheryl Crow or Madonna. When the latter pair hit their 40s, they transformed their bodies into ruthlessly efficient workout machines. Their arms now have the tensile strength of Kevlar. By contrast, Björk began the press campaign for her new album by leaking the album's cover image: a picture of the singer costumed as an armless, psychedelic Oompa-Loompa with giant blue feet. That's what I call glamour! You tell me who's more empowered.