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  2. Napkin ring problem - Wikipedia

    en.wikipedia.org/wiki/Napkin_ring_problem

    Gardner, Martin (1994), "Hole in the Sphere", My best mathematical and logic puzzles, Dover Publications, p. 8 Jones, Samuel I. (1912), Mathematical Wrinkles for Teachers and Private Learners , Norwood, MA: J. B. Cushing Co. Problem 132 asks for the volume of a sphere with a cylindrical hole drilled through it, but does not note the invariance ...

  3. Schwarzschild radius - Wikipedia

    en.wikipedia.org/wiki/Schwarzschild_radius

    A classification of black holes by mass: Micro black hole and extra-dimensional black hole; Planck length; Primordial black hole, a hypothetical leftover of the Big Bang; Stellar black hole, which could either be a static black hole or a rotating black hole; Supermassive black hole, which could also either be a static black hole or a rotating ...

  4. Stepped reckoner - Wikipedia

    en.wikipedia.org/wiki/Stepped_reckoner

    The stepped reckoner or Leibniz calculator was a mechanical calculator invented by the German mathematician ... the machine performing one addition for each hole ...

  5. Boyer–Lindquist coordinates - Wikipedia

    en.wikipedia.org/wiki/Boyer–Lindquist_coordinates

    In the mathematical description of general relativity, the Boyer–Lindquist coordinates [1] are a generalization of the coordinates used for the metric of a Schwarzschild black hole that can be used to express the metric of a Kerr black hole. The Hamiltonian for particle motion in Kerr spacetime is separable in Boyer–Lindquist coordinates.

  6. Surface gravity - Wikipedia

    en.wikipedia.org/wiki/Surface_gravity

    The surface gravity, g, of an astronomical object is the gravitational acceleration experienced at its surface at the equator, including the effects of rotation. The surface gravity may be thought of as the acceleration due to gravity experienced by a hypothetical test particle which is very close to the object's surface and which, in order not to disturb the system, has negligible mass.

  7. Torricelli's law - Wikipedia

    en.wikipedia.org/wiki/Torricelli's_law

    It consists of a pot with a small hole at the bottom through which the water can escape. The amount of escaping water gives the measure of time. As given by the Torricelli's law, the rate of efflux through the hole depends on the height of the water; and as the water level diminishes, the discharge is not uniform.

  8. Schwarzschild metric - Wikipedia

    en.wikipedia.org/wiki/Schwarzschild_metric

    A Schwarzschild black hole is described by the Schwarzschild metric, and cannot be distinguished from any other Schwarzschild black hole except by its mass. The Schwarzschild black hole is characterized by a surrounding spherical boundary, called the event horizon , which is situated at the Schwarzschild radius ( r s {\displaystyle r_{\text{s ...

  9. Genus (mathematics) - Wikipedia

    en.wikipedia.org/wiki/Genus_(mathematics)

    In layman's terms, the genus is the number of "holes" an object has ("holes" interpreted in the sense of doughnut holes; a hollow sphere would be considered as having zero holes in this sense). [3] A torus has 1 such hole, while a sphere has 0. The green surface pictured above has 2 holes of the relevant sort. For instance: