Astrophysics
Black hole
A black hole is a region of spacetime where gravity is so intense that nothing—not even light—can escape. Predicted by general relativity and supported by extensive observations, black holes span a wide range of masses from stellar remnants to supermassive objects at galactic centers. Direct imaging, stellar dynamics, X-ray observations, and gravitational-wave detections provide multiple, independent lines of evidence for their existence.
Dark Matter
Dark matter is a form of matter that does not interact with electromagnetic radiation, making it invisible to current detection methods. Its existence is inferred from gravitational effects on visible matter, such as the rotational speeds of galaxies and gravitational lensing.
General relativity
General relativity is a 1915 theory of gravitation developed by Albert Einstein that models gravity as the curvature of spacetime produced by energy and momentum. It underpins modern astrophysics and cosmology, predicting phenomena such as black holes, gravitational waves, gravitational lensing, and the expansion of the universe, and has been repeatedly confirmed by high-precision experiments and observations.
Quasar
A quasar is an extremely luminous active galactic nucleus powered by a supermassive black hole, emitting energy across the electromagnetic spectrum and often outshining its host galaxy.