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Physics portal; Bentley's paradox – Cosmological paradox involving gravity; Gauss's law for gravity – Restatement of Newton's law of universal gravitation; Jordan and Einstein frames – different conventions for the metric tensor, in a theory of a dilaton coupled to gravity
In physics, gravity (from Latin gravitas 'weight' [1]) is a fundamental interaction primarily observed as mutual attraction between all things that have mass.Gravity is, by far, the weakest of the four fundamental interactions, approximately 10 38 times weaker than the strong interaction, 10 36 times weaker than the electromagnetic force and 10 29 times weaker than the weak interaction.
A common misconception occurs between centre of mass and centre of gravity.They are defined in similar ways but are not exactly the same quantity. Centre of mass is the mathematical description of placing all the mass in the region considered to one position, centre of gravity is a real physical quantity, the point of a body where the gravitational force acts.
In physics, specifically classical mechanics, the three-body problem is to take the initial positions and velocities (or momenta) of three point masses that orbit each other in space and calculate their subsequent trajectories using Newton's laws of motion and Newton's law of universal gravitation. [1]
In classical mechanics, a gravitational field is a physical quantity. [5] A gravitational field can be defined using Newton's law of universal gravitation.Determined in this way, the gravitational field g around a single particle of mass M is a vector field consisting at every point of a vector pointing directly towards the particle.
For two pairwise interacting point particles, the gravitational potential energy is the work done by the gravitational force in bringing the masses together: = =, where is the displacement vector between the two particles and denotes the scalar product.
General relativity has emerged as a highly successful model of gravitation and cosmology, which has so far passed many unambiguous observational and experimental tests. However, there are strong indications that the theory is incomplete. [210] The problem of quantum gravity and the question of the reality of spacetime singularities remain open ...
On the other hand, there are many interesting open questions, and in particular, the theory as a whole is almost certainly incomplete. [43] In contrast to all other modern theories of fundamental interactions, general relativity is a classical theory: it does not include the effects of quantum physics.