# Spherinder

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 or circle×square), the duocylinder (2-ball × 2-ball) and the **spherinder** (3-ball × 1-ball). These constructions correspond to the five partitions of 4, the number of dimensions.

## Related 4-polytopes

It is related to the uniform prismatic polychora, which are cartesian product of a regular or semiregular polyhedron and a line segment. For example: tetrahedral prism, truncated tetrahedral prism, cubic prism, cuboctahedral prism, octahedral prism, rhombicuboctahedral prism, truncated cubic prism, truncated octahedral prism, truncated cuboctahedral prism, snub cubic prism, dodecahedral prism, icosidodecahedral prism, icosahedral prism, truncated dodecahedral prism, rhombicosidodecahedral prism, truncated icosahedral prism, truncated icosidodecahedral prism, and the snub dodecahedral prism.

## See also

## References

*The Fourth Dimension Simply Explained*, Henry P. Manning, Munn & Company, 1910, New York. Available from the University of Virginia library. Also accessible online: The Fourth Dimension Simply Explained—contains a description of duoprisms and duocylinders (double cylinders)*The Visual Guide To Extra Dimensions: Visualizing The Fourth Dimension, Higher-Dimensional Polytopes, And Curved Hypersurfaces*, Chris McMullen, 2008, ISBN 978-1438298924