General relativity Reference Libraries

Black Hole -- Black holes are objects so dense that not even light can escape their gravity. They are believed to form from the gravitational collapse of astronomical objects containing two or more solar masses. Astronomical observations suggest that the center of most galaxies, including our own Milky Way, contain supermassive black holes containing millions to billions of solar masses....

Big Bang -- The Big Bang theory is the dominant theory in cosmology about the early development and current shape of the universe. According to this theory, the universe expanded rapidly starting 13.7 0.2 billion years ago. Extrapolating the history of the universe backwards using current physical models leads to a gravitational singularity, at which all distances become zero and...