OPTIMISM IS almost a dirty word these days. Global warming, the situation in Iraq, poverty, AIDS and other seemingly unsolvable problems can make us feel a bit blue. To our rescue comes John Brockman, from the Edge World Question Center. This year's poser: What are you optimistic about? "While conventional wisdom tells us that things are bad and getting worse, scientists and the science-minded among us see good news in the coming years." This is the 10th anniversary of the Annual Question; 160 thinkers weighed in.