Cosmos
A synonym for the universe, the cosmos is the entirety of matter and energy. The word cosmos derives from the Greek word kosmos meaning the structure and harmony of the entire world.
The entire physical universe, all matter and energy, comprise the cosmos. Matter is any physical substance that occupies space and has mass. The smallest and most basic units of matter are subatomic particles, like protons, quarks, positrons, neutrinos, and electrons. The identity of a singular unifying subatomic unit that comprises all matter in the cosmos remains elusive. Energy, in contrast, is an ambiguous concept, a function of state, that can most usefully be described as the capacity to do work. Energy exists in many forms, including potential and kinetic energy.
Occasionally, the term cosmos is improperly used to denote the universe apart from Earth. In its truest sense, however, the cosmos includes the Earth as well. Early theories regarding the structure of the cosmos reflected indigenous religious philosophies. Although ancient Greek philosophers and scientists offered proof that the Earth was spherical and that it rotated about the Sun, such proofs were rejected upon religious grounds. The Ptolemaic model, formalized in the second century, held that the Earth was the center of the Cosmos, with the stars and planets rotating about it. In Western science, because the Ptolemaic view was embraced by the Christian church, it was only with considerable controversy that this view discarded in the 16th century in favor of the Copernican theory which held that the Sun was the center of the cosmos. Subsequent observations by astronomers led to a realization that the Sun and its system of planets are but one small system located on a spiral arm of in a vast galaxy termed the Milky Way that is comprised of billions of stars. Moreover, the Milky Way galaxy is but one among billions of other galaxies in the observable universe.
The known cosmos contains gigantic masses of ionized gases called nebulae (singular nebula), rapidly rotating neutron stars called pulsars that emit oscillating bursts of electromagnetic radiation, black holes consisting of immeasurably dense matter from which light can not escape, and many other objects of interest to astronomers. The cosmos is dynamic. Supernova explosions resulting from the gravitational collapse of stars propel matter in all directions to aid in the formation of new nebulae in which new stars are created by gravitational forces. The cosmos is expanding, and some current estimates predict the width of the cosmos to be least 10-15 billion light-years in diameter.
The study of the structure, components, origins, and evolution of the universe is called cosmology. A cornerstone of modern cosmology is the big bang theory, which accounts for the creation of the material universe and the evolution of physical laws from an explosion that occurred approximately 10-20 billion years ago. The explosion is postulated to have occurred from an immeasurably dense singularity, or dimensionless point that contained all of the matter and energy of the current cosmos. After the big bang, the universe was extremely hot and began expanding, creating space as it expanded. As the cosmos cooled it allowed the formation of subatomic particles, atoms which in turn evolved the material universe.
This is the complete article, containing 529 words
(approx. 2 pages at 300 words per page).
