Great rock bands tend to be built for sprints rather than marathons. They come and go in brief bursts of glory, usually torn apart by internal problems or the inability to maintain a creative edge. Nirvana was gone in the blink of an eye. The Beatles never really made it out of the '60s.
All this makes U2 unique.
One reason for the band's continued relevance after a quarter-century is that the quartet keeps challenging itself -- never more so than in the captivating new world tour, which began Monday at San Diego's Sports Arena.
U2's latest album, "How to Dismantle an Atomic Bomb," is a thoughtful, deeply personal look at faith, family and rejuvenation; not exactly easy themes to build an arena rock show around. Yet the band brought the spirit of the album to the stage in a two-hour set that was as warm and eloquent as the songs.