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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

    Fluid friction describes the friction between layers of a viscous fluid that are moving relative to each other. [7] [8] 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.

  4. List of unsolved problems in astronomy - Wikipedia

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

    Why is the Sun's corona so much hotter than the Sun's surface? Why is the magnetic reconnection effect many orders of magnitude faster than predicted by standard models? Space weather prediction: How does the Sun produce strong southward-pointing magnetic fields in solar coronal mass ejections that lead to geomagnetic storms?

  5. Two-body problem in general relativity - Wikipedia

    en.wikipedia.org/wiki/Two-body_problem_in...

    The motion of the lighter body (called the "particle" below) can then be determined from the Schwarzschild solution; the motion is a geodesic ("shortest path between two points") in the curved space-time. Such geodesic solutions account for the anomalous precession of the planet Mercury, which is a key piece of evidence supporting the theory of ...

  6. 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 ...

  7. 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 ...

  8. Newton's law of universal gravitation - Wikipedia

    en.wikipedia.org/wiki/Newton's_law_of_universal...

    Assuming SI units, F is measured in newtons (N), m 1 and m 2 in kilograms (kg), r in meters (m), and the constant G is 6.674 30 (15) × 10 −11 m 3 ⋅kg −1 ⋅s −2. [12] The value of the constant G was first accurately determined from the results of the Cavendish experiment conducted by the British scientist Henry Cavendish in 1798 ...

  9. Einstein-aether theory - Wikipedia

    en.wikipedia.org/wiki/Einstein-aether_theory

    In physics the Einstein-aether theory, also called aetheory, is the name coined in 2004 for a modification of general relativity that has a preferred reference frame and hence violates Lorentz invariance. These generally covariant theories describes a spacetime endowed with both a metric and a unit timelike vector field named the aether.