Dark matter is a hypothetical kind of matter that cannot be seen with telescopes but would account for most of the matter in the universe. The existence and properties of dark matter are inferred from its gravitational effects on visible matter, radiation, and the large-scale structure of the universe. Dark matter has not been detected directly, making it one of the greatest mysteries in modern astrophysics. Dark matter neither emits nor absorbs light, or any other electromagnetic radiation, at any significant level. According to the Planck mission team, and based on the standard model of...

Proof theory is a branch of mathematical logic that represents proofs as formal mathematical objects, facilitating their analysis by mathematical techniques. Proofs are typically presented as inductively-defined data structures such as plain lists, boxed lists, or trees, which are constructed according to the axioms and rules of inference of the logical system. As such, proof theory is syntactic in nature, in contrast to model theory, which is semantic in nature. Together with model theory, axiomatic set theory, and recursion theory, proof theory is one of the so-called four pillars of the...

A government is the system by which a state or community is controlled. In the case of its broad associative definition, government normally consists of legislators, administrators, and arbitrators. Government is the means by which state policy is enforced, as well as the mechanism for determining the policy of the state. A form of government, or form of state governance, refers to the set of political systems and institutions that make up the organization of a specific government. Government of any kind currently affects every human activity in many important ways. For this reason, political...