Sphere Definition and 1000 Threads

A sphere (from Greek σφαῖρα—sphaira, "globe, ball") is a geometrical object in three-dimensional space that is the surface of a ball (viz., analogous to the circular objects in two dimensions, where a "circle" circumscribes its "disk").
Like a circle in a two-dimensional space, a sphere is defined mathematically as the set of points that are all at the same distance r from a given point in a three-dimensional space. This distance r is the radius of the ball, which is made up from all points with a distance less than (or, for a closed ball, less than or equal to) r from the given point, which is the center of the mathematical ball. These are also referred to as the radius and center of the sphere, respectively. The longest straight line segment through the ball, connecting two points of the sphere, passes through the center and its length is thus twice the radius; it is a diameter of both the sphere and its ball.
While outside mathematics the terms "sphere" and "ball" are sometimes used interchangeably, in mathematics the above distinction is made between a sphere, which is a two-dimensional closed surface embedded in a three-dimensional Euclidean space, and a ball, which is a three-dimensional shape that includes the sphere and everything inside the sphere (a closed ball), or, more often, just the points inside, but not on the sphere (an open ball). The distinction between ball and sphere has not always been maintained and especially older mathematical references talk about a sphere as a solid. This is analogous to the situation in the plane, where the terms "circle" and "disk" can also be confounded.

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  1. K

    B Matrices of su(3) and sphere symmetry

    i used to get pauli matrices by the following steps it uses the symmetry of a complex plane sphere i guess so..? however i can't get the 8 gell mann matrices please help ! method*: (x y) * (a b / c d ) = (x' y') use |x|^2 + |y|^2 = |x'|^2 + |y'|^2 and |x| = x * x(complex conjugate) this way...
  2. Vitani11

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  3. doktorwho

    Calculating Total Charge on Non-Uniformly Charged Sphere

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  4. G

    Shielding an off-center charge with a conducting shell

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  5. S

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  6. 1

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  7. Jezza

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  8. J

    What is the electrostatic potential energy of a sphere?

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  9. 1

    Center of mass of a sphere with cavity removed

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  10. F

    I Deriving the volume of a sphere using semi-circles

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  11. FallenApple

    No Potential Energy due to Sphere of Mass?

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  12. karush

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  13. nysnacc

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  14. Destroxia

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  15. E

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  16. D

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  17. W

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  18. TheDemx27

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  19. M

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  20. J

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  21. C

    I Why is the limit of θ from 0 to π in the formula for surface area of a sphere?

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  22. G

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  23. ReidMerrill

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  24. S

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  25. O

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  26. O

    I Why is the E-field inside a solid conducting sphere zero?

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  27. N

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  28. G Cooke

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  29. JulienB

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  30. dumbdumNotSmart

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  31. K

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  32. Turbodog66

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  33. Khatti

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  34. G

    Uniform E field for spherical shell.

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  35. Prasun-rick

    I Volume of sphere using integration?

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  36. T

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  37. C

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  38. I

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  39. I

    Rotations around the x and y axes of stereographic sphere

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  40. C

    Contact area of ideal sphere resting on flat surface

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  41. NicolasPan

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  42. A

    I Calculating the Surface Area of a Sphere: How Does it Differ?

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  43. K

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  44. Spinnor

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  45. ChrisVer

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  46. P

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  47. S

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  48. E

    I Fermi sphere and density of states

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  49. Z

    What is the moment of inertia of a sphere and how is it derived?

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  50. L

    I Universe is a sphere that is centered on any observer? How?

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