Read the passage from "Zero-Gravity Nutrition." Weightlessness can be an adventure. In space, there is no gravity. What goes up does not come down. Without gravity food floats. While weightlessness may be a thrill, it is a problem for eating. Food scientists design meals that won't fall apart and float away. Which sentence from the passage best expresses the central idea? Weightlessness can be an adventure. What goes up-does not come down. While weightlessness may be a thrill, it is a problem for eating. Food scientists design meals that won't fall apart and float away.