Material constituents such as particles and their composites. In cosmology, the narrower phrase pressureless matter usually refers to nonrelativistic components whose rest energy dominates their random kinetic energy, giving negligible pressure and density proportional to the inverse cube of the scale factor. This usage distinguishes the matter contribution from relativistic radiation in cosmology and vacuum energy.
Articles by others on the same topic
Matter is anything that has mass and occupies space. It is composed of particles, which can be atoms or molecules, and it exists in various states, primarily solid, liquid, and gas. In some contexts, it can also include plasma, which is a high-energy state of matter where electrons are separated from atoms. Matter has properties such as volume, density, and viscosity, and it can undergo physical and chemical changes.