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In four-dimensional geometry, the spherinder, or spherical cylinder or spherical prism, is a geometric object, defined as the Cartesian product of a 3-ball (or solid 2-sphere), radius ''r''1 and a line segment of radius ''r''2: : Like the duocylinder, it is also analogous to a cylinder in 3-space, which is the Cartesian product of a disk with a line segment. It can be seen in 3-dimensional space by stereographic projection as two concentric spheres, in a similar way that a tesseract (cubic prism) can be projected as two concentric cubes. ==Relation to other shapes== In 3-space, a cylinder can be considered intermediate between a cube and a sphere. In 4-space there are three intermediate forms between the tesseract (1-ball × 1-ball × 1-ball × 1-ball) and the hypersphere (4-ball). They are the: *cubinder (2-ball × 1-ball × 1-ball), whose surface consists of four cylindrical cells and one square torus. *spherinder (3-ball × 1-ball), whose surface consists of three cells - two spheres, and the region in between. *duocylinder (2-ball × 2-ball), whose surface consists of two toroidal cells. These constructions correspond to the five partitions of 4, the number of dimensions. If the two ends of a spherinder are connected together, or equivalently if a sphere is dragged around a circle perpendicular to its 3-space, it traces out a spheritorus. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「spherinder」の詳細全文を読む スポンサード リンク
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