Cosmic gas refers to the diffuse gas present in the interstellar and intergalactic medium in the universe. This gas primarily consists of hydrogen and helium, along with trace amounts of heavier elements. Cosmic gas plays a crucial role in various astrophysical processes, such as star formation, galactic evolution, and the interplay between galaxies and their surrounding environment. Researchers study cosmic gas through observations using telescopes and other instruments to better understand its properties and dynamics, as well as its impact on the evolution of the universe.