Commentary: A More Perfect Astronaut

摘要

Even when one is inside a climate-controlled spacecraft, sheltered from the deadly vacuum outside, space is a hostile setting. Terrestrial organisms venturing off the planet face a number of threats, chief among them cosmic radiation and the near absence of gravity. In space, medaka fish become disoriented, turning continuous somersaults as they swim. Rats cease to use their hind limbs effectively. For humans, problems include the wasting of postural muscles, the demineralization of bone, and the often disquieting sensation of being upside down.