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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. Spacecraft flight dynamics - Wikipedia

    en.wikipedia.org/wiki/Spacecraft_flight_dynamics

    A space vehicle's flight is determined by application of Newton's second law of motion: =, where F is the vector sum of all forces exerted on the vehicle, m is its current mass, and a is the acceleration vector, the instantaneous rate of change of velocity (v), which in turn is the instantaneous rate of change of displacement.

  4. Skin friction drag - Wikipedia

    en.wikipedia.org/wiki/Skin_friction_drag

    Skin friction drag is a type of aerodynamic or hydrodynamic drag, which is resistant force exerted on an object moving in a fluid.Skin friction drag is caused by the viscosity of fluids and is developed from laminar drag to turbulent drag as a fluid moves on the surface of an object.

  5. Fundamental interaction - Wikipedia

    en.wikipedia.org/wiki/Fundamental_interaction

    During the Scientific Revolution, Galileo Galilei experimentally determined that this hypothesis was wrong under certain circumstances—neglecting the friction due to air resistance and buoyancy forces if an atmosphere is present (e.g. the case of a dropped air-filled balloon vs a water-filled balloon), all objects accelerate toward the Earth ...

  6. Aether theories - Wikipedia

    en.wikipedia.org/wiki/Aether_theories

    Isaac Newton suggests the existence of an aether in the Third Book of Opticks (1st ed. 1704; 2nd ed. 1718): "Doth not this aethereal medium in passing out of water, glass, crystal, and other compact and dense bodies in empty spaces, grow denser and denser by degrees, and by that means refract the rays of light not in a point, but by bending them gradually in curve lines? ...

  7. 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 ...

  8. Worldsheet - Wikipedia

    en.wikipedia.org/wiki/Worldsheet

    In string theory, a worldsheet is a two-dimensional manifold which describes the embedding of a string in spacetime. [1] The term was coined by Leonard Susskind [2] as a direct generalization of the world line concept for a point particle in special and general relativity.

  9. Vacuum energy - Wikipedia

    en.wikipedia.org/wiki/Vacuum_energy

    A field in physics may be envisioned as if space were filled with interconnected vibrating balls and springs, and the strength of the field is like the displacement of a ball from its rest position. The theory requires "vibrations" in, or more accurately changes in the strength of, such a field to propagate as per the appropriate wave equation ...