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  2. Powellite - Wikipedia

    en.wikipedia.org/wiki/Powellite

    It has a Mohs hardness of 3.5 to 4 and a specific gravity of 4.25. It forms a solid solution series with scheelite (calcium tungstate, CaWO 4). It has refractive index values of n ω =1.974 and n ε =1.984. [3]

  3. Dust solution - Wikipedia

    en.wikipedia.org/wiki/Dust_solution

    In general relativity, a dust solution is a fluid solution, a type of exact solution of the Einstein field equation, in which the gravitational field is produced entirely by the mass, momentum, and stress density of a perfect fluid that has positive mass density but vanishing pressure.

  4. AOL Mail

    mail.aol.com

    Get AOL Mail for FREE! Manage your email like never before with travel, photo & document views. Personalize your inbox with themes & tabs. You've Got Mail!

  5. Poisson's equation - Wikipedia

    en.wikipedia.org/wiki/Poisson's_equation

    Siméon Denis Poisson. Poisson's equation is an elliptic partial differential equation of broad utility in theoretical physics.For example, the solution to Poisson's equation is the potential field caused by a given electric charge or mass density distribution; with the potential field known, one can then calculate the corresponding electrostatic or gravitational (force) field.

  6. Shell theorem - Wikipedia

    en.wikipedia.org/wiki/Shell_theorem

    A spherically symmetric body affects external objects gravitationally as though all of its mass were concentrated at a point at its center. If the body is a spherically symmetric shell (i.e., a hollow ball), no net gravitational force is exerted by the shell on any object inside, regardless of the object's location within the shell.

  7. Geopotential spherical harmonic model - Wikipedia

    en.wikipedia.org/wiki/Geopotential_spherical...

    For example, at a radius of 6600 km (about 200 km above Earth's surface) J 3 /(J 2 r) is about 0.002; i.e., the correction to the "J 2 force" from the "J 3 term" is in the order of 2 permille. The negative value of J 3 implies that for a point mass in Earth's equatorial plane the gravitational force is tilted slightly towards the south due to ...

  8. Gravity - Wikipedia

    en.wikipedia.org/wiki/Gravity

    In physics, gravity (from Latin gravitas 'weight' [1]) is a fundamental interaction primarily observed as a 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.

  9. Schwarzschild metric - Wikipedia

    en.wikipedia.org/wiki/Schwarzschild_metric

    In Einstein's theory of general relativity, the Schwarzschild metric (also known as the Schwarzschild solution) is an exact solution to the Einstein field equations that describes the gravitational field outside a spherical mass, on the assumption that the electric charge of the mass, angular momentum of the mass, and universal cosmological constant are all zero.