Houston, we have an announcement: It's World Space Week! This year, the theme is "Living in Space", so we're revisiting our best articles on the challenges and wonders of life in microgravity and on planets far from home. Spaceflight Accelerates Aging of Human Stem Cells, Study Finds The rigors of space travel could accelerate changes in the human body usually associated with aging. According to a new study of human tissues sent into low-Earth orbit, time in space reduces cell production,