But to a scientist, the word fluid means much more. A fluid is any liquid or gaseous material that flows and, in gravity, assumes the shape of the container it is in.
Scientists are interested in fluids for a variety of reasons.
Fluids are an important part of life processes, from the blood in our veins and arteries to the oxygen in the air. The properties of fluids make plumbing, automobiles, and even fluorescent lighting possible. Fluid mechanics describes many processes that occur within the human body and also explains the flow of sap through plants. The preparation of materials often involves a fluid state that ultimately has a strong impact on the characteristics of the final product. Studying these phenomena in microgravity allows the scientists to examine processes and conditions impossible to study when influenced by Earth's gravity.