Sphere
round, rotationally symmetric shape of the 2D surface of a ball in 3D space
A sphere is a surface analogous to the circle, a curve. In solid geometry, a sphere is the set of points that are all at the same distance r from a given point in three-dimensional space. That given point is the center of the sphere, and the distance r is the sphere's radius. The earliest known mentions of spheres appear in the work of the ancient Greek mathematicians.
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Quotes
edit- This is as I have said in my Arithmetic:—The area of a circle is equal to the product of the circumference by one-fourth of the diameter [πr²]. That result multiplied by 4 gives the surface of the sphere [4πr²], which is like the net surrounding a hand ball; the same (surface of a sphere) when multiplied by the diameter and divided by six [4/3πr³] becomes invariably the volume of the sphere.
- Bhāskara II (d. 1185), reported in P. C. Sengupta, "Infinitesimal Calculus in Indian Mathematics—Its Origin and Development", Journal of the Department of Letters, vol. 22 (Calcutta UP, 1932) p. 16. Notes in square brackets added in C. K. Raju, "Calculus Transmission", Helaine Selin (ed.) Encyclopedia of Non-Western Science, Technology and Medicine (Dordrecht: Springer, 2016) pp. 1016–22
- A sphere is a solid figure described by the revolution of a semicircle about its diameter, which remains fixed.The axis of a sphere is the fixed straight line about which the semicircle revolves.The centre of a sphere is the same with that of the semicircle.The diameter of a sphere is any straight line which passes through the centre, and is terminated both ways by the superficies of the sphere.
