Venturing into space is not without risk. In space, the disorienting feeling of weightlessness is more correctly termed microgravity, an environment in which there is very little net gravitational force. This causes mental disorientation, or space motion sickness. Microgravity also causes body fluid circulation to change, resulting in the “Puffy-Head Bird-Legs” Syndrome. It also results in osteoporosis, thinning and weakening of the bones. Radiation, one of the more serious dangers, damages cells, and long term exposure to loud noises given off by machinery results in hearing loss. Collisions with space debris may also occur and can be fatal. There are even psychological dangers to space travel. Despite these dangers, many astronauts find scientific exploration worth the risk.