Feb 12, 2026 · universe, the whole cosmic system of matter and energy of which Earth, and therefore the human race, is a part. Humanity has traveled a long road since societies imagined Earth, the …

Feb 13, 2026 · Big-bang model, widely held theory of the evolution of the universe. Its essential feature is the emergence of the universe from a state of extremely high temperature and density—the so …

4 days ago · The term science describes any system of knowledge that is concerned with the physical world and its phenomena and that entails unbiased observations and systematic experimentation. In …

Jan 25, 2026 · Cosmology, the field of study that brings together the natural sciences, particularly astronomy and physics, in a joint effort to understand the physical universe as a unified whole. When …

Jan 25, 2026 · Galaxy, any of the systems of stars and interstellar matter that make up the universe. Many such assemblages are so enormous that they contain hundreds of billions of stars. Virtually all …

Feb 20, 2026 · Dark matter, a component of the universe whose presence is discerned from its gravitational attraction rather than its luminosity.

Feb 11, 2026 · Astronomy, science that encompasses the study of all extraterrestrial objects and phenomena. Since the late 19th century, astronomy has expanded to include astrophysics, the …

Observable universe, the region of space that humans can actually or theoretically observe with the aid of technology. The observable universe, which can be thought of as a bubble with Earth at its centre, …

Jan 20, 2026 · Star, any massive self-luminous celestial body of gas that shines by radiation derived from its internal energy sources. This article describes the properties and evolution of individual …

The universe is also called the cosmos. Cosmology is the branch of science that studies the universe as a whole. Astronomy is another name for the study of the universe. Scientists use telescopes and …