- Apsis
- Aphelion
- Perihelion
- 近点・遠点
- Gravitational lensing
- Einstein Ring
- Detection of Gravitational Waves (from Merging Black Holes)
- Rotation velocity of a galaxy
- Bekenstein & Hawking's Black Hole Thought Experiments
- Black holes emit radiation
$$S = {Area \over 4Gℏ}c^3$$
The amount of information is determined by the area of the black hole horizon.