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  2. Plane (Dungeons & Dragons) - Wikipedia

    en.wikipedia.org/wiki/Plane_(Dungeons_&_Dragons)

    They consist of the Elemental Planes [1] of air, earth, fire and water, and the Energy Planes. Some descriptions also contain the Para-elemental (magma, ice, etc.) and Quasi-elemental planes (lightning, dust, etc.) linking them. [1] The energy planes are the Positive Material Plane and Negative Material Plane.

  3. Orbital plane of reference - Wikipedia

    en.wikipedia.org/wiki/Orbital_plane_of_reference

    The plane tangent to celestial sphere for extrasolar objects; On the plane of reference, a zero-point must be defined from which the angles of longitude are measured. This is usually defined as the point on the celestial sphere where the plane crosses the prime hour circle (the hour circle occupied by the First Point of Aries), also known as ...

  4. Euclidean planes in three-dimensional space - Wikipedia

    en.wikipedia.org/wiki/Euclidean_planes_in_three...

    The attitude of a lattice plane is the orientation of the line normal to the plane, [12] and is described by the plane's Miller indices. In three-space a family of planes (a series of parallel planes) can be denoted by its Miller indices (hkl), [13] [14] so the family of planes has an attitude common to all its constituent planes.

  5. Astronomical coordinate systems - Wikipedia

    en.wikipedia.org/wiki/Astronomical_coordinate...

    The poles are located at ±90° from the fundamental plane. The primary direction is the starting point of the longitudinal coordinates. The origin is the zero distance point, the "center of the celestial sphere", although the definition of celestial sphere is ambiguous about the definition of its center point.

  6. Quasi-sphere - Wikipedia

    en.wikipedia.org/wiki/Quasi-sphere

    In a space with a positive-definite quadratic form (i.e. a Euclidean space), a quasi-sphere with negative radial scalar square is the empty set, one with zero radial scalar square consists of a single point, one with positive radial scalar square is a standard n-sphere, and one with zero curvature is a hyperplane that is partitioned with the n ...

  7. List of quasiparticles - Wikipedia

    en.wikipedia.org/wiki/List_of_quasiparticles

    Particle with zero mass gap in one direction of space. electron Surface magnon polariton: Coupling between spin waves and electromagnetic waves. magnon, photon Surface phonon: Vibrational modes in a crystal lattice associated with atomic shifts at the surface. Surface plasmon: A coherent excitation of a plasma at the surface of a metal.

  8. Sphere of influence (astrodynamics) - Wikipedia

    en.wikipedia.org/wiki/Sphere_of_influence_(astro...

    Because the definition of r SOI relies on the presence of the Sun and a planet, the term is only applicable in a three-body or greater system and requires the mass of the primary body to be much greater than the mass of the secondary body. This changes the three-body problem into a restricted two-body problem.

  9. Halo orbit - Wikipedia

    en.wikipedia.org/wiki/Halo_orbit

    A halo orbit is a periodic, three-dimensional orbit associated with one of the L 1, L 2 or L 3 Lagrange points in the three-body problem of orbital mechanics.Although a Lagrange point is just a point in empty space, its peculiar characteristic is that it can be orbited by a Lissajous orbit or by a halo orbit.