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  2. List of NP-complete problems - Wikipedia

    en.wikipedia.org/wiki/List_of_NP-complete_problems

    The problem for graphs is NP-complete if the edge lengths are assumed integers. The problem for points on the plane is NP-complete with the discretized Euclidean metric and rectilinear metric. The problem is known to be NP-hard with the (non-discretized) Euclidean metric. [3]: ND22, ND23

  3. List of unsolved problems in physics - Wikipedia

    en.wikipedia.org/wiki/List_of_unsolved_problems...

    Some of the major unsolved problems in physics are theoretical, meaning that existing theories seem incapable of explaining a certain observed phenomenon or experimental result. The others are experimental, meaning that there is a difficulty in creating an experiment to test a proposed theory or investigate a phenomenon in greater detail.

  4. Fermi problem - Wikipedia

    en.wikipedia.org/wiki/Fermi_problem

    A Fermi problem (or Fermi question, Fermi quiz), also known as an order-of-magnitude problem, is an estimation problem in physics or engineering education, designed to teach dimensional analysis or approximation of extreme scientific calculations. Fermi problems are usually back-of-the-envelope calculations.

  5. Three-body problem - Wikipedia

    en.wikipedia.org/wiki/Three-body_problem

    The three-body problem is a special case of the n-body problem, which describes how n objects move under one of the physical forces, such as gravity. These problems have a global analytical solution in the form of a convergent power series, as was proven by Karl F. Sundman for n = 3 and by Qiudong Wang for n > 3 (see n -body problem for details).

  6. Navier–Stokes existence and smoothness - Wikipedia

    en.wikipedia.org/wiki/Navier–Stokes_existence...

    In mathematics, the Navier–Stokes equations are a system of nonlinear partial differential equations for abstract vector fields of any size. In physics and engineering, they are a system of equations that model the motion of liquids or non-rarefied gases (in which the mean free path is short enough so that it can be thought of as a continuum mean instead of a collection of particles) using ...

  7. Solution of triangles - Wikipedia

    en.wikipedia.org/wiki/Solution_of_triangles

    Solve any plane triangle problem with the minimum of input data. Drawing of the solved triangle. TriSph – Free software to solve the spherical triangles, configurable to different practical applications and configured for gnomonic. Spherical Triangle Calculator – Solves spherical triangles. TrianCal – Triangles solver by Jesus S.

  8. Two-body problem - Wikipedia

    en.wikipedia.org/wiki/Two-body_problem

    The two-body problem is interesting in astronomy because pairs of astronomical objects are often moving rapidly in arbitrary directions (so their motions become interesting), widely separated from one another (so they will not collide) and even more widely separated from other objects (so outside influences will be small enough to be ignored safely).

  9. Illumination problem - Wikipedia

    en.wikipedia.org/wiki/Illumination_problem

    Solutions to the illumination problem by George W. Tokarsky (26 sides) and David Castro (24 sides) This problem was also solved for polygonal rooms by George Tokarsky in 1995 for 2 and 3 dimensions, which showed that there exists an unilluminable polygonal 26-sided room with a "dark spot" which is not illuminated from another point in the room ...