"One of the first things they teach at the Academy is how to deal with motion sickness. Many of the large stations, especially the interplanetary ones, are Ring-types, which have a habitable outer ring attached to some center structure. These stations rotate, creating an artificial 'gravity' via centripetal acceleration. However, those with more sensitive inner ears can detect this motion. This is often exasperated when one looks out of a window and sees the stars moving. Experienced Explorers barely notice anything. But those who are just learning may experience some... unpleasantness."