Search results
Results from the WOW.Com Content Network
Dark matter is a hypothetical form of matter that does not interact with light or electromagnetism, but only with gravity. It is inferred by its gravitational effects on galaxies, clusters and the cosmic microwave background. Learn about its history, evidence and possible candidates.
Outer space is the expanse that exists beyond Earth's atmosphere and between celestial bodies. It has a near-perfect vacuum of plasma, radiation, magnetic fields and dust, and its size and shape are determined by the Big Bang theory and the cosmic microwave background.
The interstellar medium (ISM) is the matter and radiation that exists in the space between the star systems in a galaxy. It includes gas, dust, cosmic rays, and electromagnetic radiation, and has different phases and properties depending on temperature, density, and composition.
Dark energy is an unknown form of energy that drives the accelerating expansion of the universe. It is not created by particle annihilation, but by a cosmological constant or a scalar field. Learn more about its discovery, nature and candidates.
The Friedmann equations are a set of equations that govern the expansion of space in homogeneous and isotropic models of the universe. The critical density of the universe is the density that determines the geometry of the universe to be flat, and it is estimated to be about five atoms per cubic metre.
Matter is any substance that has mass and takes up space, and is composed of atoms or subatomic particles. Learn about the different states, phases, and properties of matter, as well as the history and philosophy of the concept of matter in science.
Plasma is one of the four fundamental states of matter, characterized by the presence of charged particles in any combination of ions or electrons. Learn about the history, characteristics, and types of plasma, as well as how it differs from solid, liquid, and gas.
Gas is one of the four fundamental states of matter, composed of individual atoms, molecules or compounds. Learn about the physical characteristics, behavior and applications of gases, as well as the history and etymology of the term.