There have been many revolutions over the last century, but perhaps none as significant as the longevity revolution. We are living on average today 34 years longer than our great-grandparents did. That's an entire second adult lifespan that's been added to our lifetime. And yet for the most part, our culture has not come to terms with what this means, says actor and activist, Jane Fonda. We're still living with the old paradigm of age as an arch: You are born, you peak at midlife and decline...