Spending time in the weightless environment of microgravity can have some dramatic effects on the human body , but scientists have recently discovered a new one that could help explain why some astronauts struggle to adjust after returning to Earth. Following a stint in space as short as a few weeks, astronauts can develop measurable changes in the very shape of their brains. For longer stretches of space travel, the alterations can linger for at least six months. These shifts are subtle – just