The number of elderly Americans is rising sharply. More than 1 million people will be at least 100 years old by 2050 -- up from just 50,000 centenarians in 2000. With more and more Americans living longer, policymakers worry that Social Security and Medicare costs will drain money from health and education programs for the young. Meanwhile, researchers are trying to prolong life even more, making old age a time of health and activity, not sickness and frailty. Some envision a future when people routinely live in good health to 100 or longer, aided, perhaps, by drugs that turn on "longevity" genes, newly discovered secrets of long-lived people and even computer chips and tiny robotic devices implanted in humans to help them remain vigorous. But many gerontologists and ethicists argue that the human body is far too complex for such drastic changes and that scientists should focus on improving health care for all Americans, not increasing longevity.

Beth Baker is an award-winning freelance journalist in Takoma Park, Md., whose articles appear in numerous publications, including The Washington Post, AARP Bulletin, Ms., and BioScience, the journal of the American Institute of Biological Sciences. She has received two National Mature Media Awards for her reporting on aging and media fellowships to study aging and cancer issues from, respectively, Case Western University and the National Press Foundation. Her books include Old Age in a New Age -- The Promise of Transformative Nursing Homes (Vanderbilt University Press, 2007). She is a former hospice volunteer.