An Aspen Lecture about the implications of increased human longevity. Laura Carstensen says the majority of children spending time on playgrounds in the developed world right now will live to be one hundred, and even older. In most of human history, life was short. What are the challenges for an aging society? Carstensen is founding director of the Stanford Center on Longevity and author of "A Long Bright Future: Happiness, Health and Financial Security in an Age of Increased Longevity."