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This curvature is caused by the presence of mass. (See: Stress–energy tensor) If the masses move, the curvature of spacetime changes. If the motion is not spherically symmetric, the motion can cause gravitational waves which propagate away at the speed of light. [10]
However, gravity is the most significant interaction between objects at the macroscopic scale, and it determines the motion of planets, stars, galaxies, and even light. On Earth, gravity gives weight to physical objects, and the Moon's gravity is responsible for sublunar tides in the oceans. The corresponding antipodal tide is caused by the ...
General relativity interprets gravity as a consequence of distortions in spacetime caused by the presence of mass, and further entails that certain movements or acceleration of these masses will cause distortions – or "ripples" – in spacetime which spread outward from the source at the speed of light.
In 1776, Laplace considered a different mechanism whereby gravity is caused by "the impulse of a fluid directed towards the centre of the attracting body". In such a theory, a finite speed of gravity results in the Earth spiraling inwards towards the Sun. [6] From a modern point of view, Laplace's analysis is incorrect.
Acoustic levitation is a method for suspending matter in air against gravity using acoustic radiation pressure from high intensity sound waves. [1] [2] It works on the same principles as acoustic tweezers by harnessing acoustic radiation forces. However acoustic tweezers are generally small scale devices which operate in a fluid medium and are ...
The gravity g′ at depth d is given by g′ = g(1 − d/R) where g is acceleration due to gravity on the surface of the Earth, d is depth and R is the radius of the Earth. If the density decreased linearly with increasing radius from a density ρ 0 at the center to ρ 1 at the surface, then ρ ( r ) = ρ 0 − ( ρ 0 − ρ 1 ) r / R , and the ...
Gravitational redshift can be interpreted as a consequence of the equivalence principle (that gravitational effects are locally equivalent to inertial effects and the redshift is caused by the Doppler effect) [5] or as a consequence of the mass–energy equivalence and conservation of energy ('falling' photons gain energy), [6] [7] though there ...
In fluid dynamics, gravity waves are waves in a fluid medium or at the interface between two media when the force of gravity or buoyancy tries to restore equilibrium. An example of such an interface is that between the atmosphere and the ocean, which gives rise to wind waves. A gravity wave results when fluid is displaced from a position of ...