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  2. Dynamical friction - Wikipedia

    en.wikipedia.org/wiki/Dynamical_friction

    The effect of dynamical friction explains why the brightest (more massive) galaxy tends to be found near the center of a galaxy cluster. The effect of the two body collisions slows down the galaxy, and the drag effect is greater the larger the galaxy mass. When the galaxy loses kinetic energy, it moves towards the center of the cluster.

  3. Friction - Wikipedia

    en.wikipedia.org/wiki/Friction

    Lubricated friction is a case of fluid friction where a lubricant fluid separates two solid surfaces. [9] [10] [11] Skin friction is a component of drag, the force resisting the motion of a fluid across the surface of a body. Internal friction is the force resisting motion between the elements making up a solid material while it undergoes ...

  4. Vacuum energy - Wikipedia

    en.wikipedia.org/wiki/Vacuum_energy

    Using the upper limit of the cosmological constant, the vacuum energy of free space has been estimated to be 10 −9 joules (10 −2 ergs), or ~5 GeV per cubic meter. [3] However, in quantum electrodynamics , consistency with the principle of Lorentz covariance and with the magnitude of the Planck constant suggests a much larger value of 10 113 ...

  5. List of unsolved problems in astronomy - Wikipedia

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

    This article is a list of notable unsolved problems in astronomy.Problems may be theoretical or experimental. Theoretical problems result from inability of current theories to explain observed phenomena or experimental results.

  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. Physics and Star Wars - Wikipedia

    en.wikipedia.org/wiki/Physics_and_Star_Wars

    According to Cavelos, astronomers hypothesize at least two possible solutions to these problems exist and that even life supporting binary star systems could exist. One scenario could be two stars billions of kilometres apart. A planet or planets would be able to orbit one star while at minimum influence of the other.

  8. Orbital mechanics - Wikipedia

    en.wikipedia.org/wiki/Orbital_mechanics

    and are the masses of objects 1 and 2, and is the specific angular momentum of object 2 with respect to object 1. The parameter θ {\displaystyle \theta } is known as the true anomaly , p {\displaystyle p} is the semi-latus rectum , while e {\displaystyle e} is the orbital eccentricity , all obtainable from the various forms of the six ...

  9. Force field (physics) - Wikipedia

    en.wikipedia.org/wiki/Force_field_(physics)

    In physics, a force field is a vector field corresponding with a non-contact force acting on a particle at various positions in space. Specifically, a force field is a vector field F {\displaystyle \mathbf {F} } , where F ( r ) {\displaystyle \mathbf {F} (\mathbf {r} )} is the force that a particle would feel if it were at the position r ...