Tesseract Information
Tesseract 8cell 4cube  

Type  Convex regular 4polytope 
Schläfli symbol  {4,3,3} t_{0,3}{4,3,2} or {4,3}×{ } t_{0,2}{4,2,4} or {4}×{4} t_{0,2,3}{4,2,2} or {4}×{ }×{ } t_{0,1,2,3}{2,2,2} or { }×{ }×{ }×{ } 
Coxeter diagram  
Cells  8 {4,3} 
Faces  24 {4} 
Edges  32 
Vertices  16 
Vertex figure 
Tetrahedron 
Petrie polygon  octagon 
Coxeter group  B_{4}, [3,3,4] 
Dual  16cell 
Properties  convex, isogonal, isotoxal, isohedral 
Uniform index  10 
In geometry, the tesseract is the fourdimensional analogue of the cube; the tesseract is to the cube as the cube is to the square.^{ [1]} Just as the surface of the cube consists of six square faces, the hypersurface of the tesseract consists of eight cubical cells. The tesseract is one of the six convex regular 4polytopes.
The tesseract is also called an eightcell, C_{8}, (regular) octachoron, octahedroid,^{ [2]} cubic prism, and tetracube.^{ [3]} It is the fourdimensional hypercube, or 4cube as a part of the dimensional family of hypercubes or measure polytopes.^{ [4]} Coxeter labels it the polytope.^{ [5]} The term "hypercube" without a dimension reference is frequently treated as a synonym for this specific shape.
According to the Oxford English Dictionary, the word tesseract was coined and first used in 1888 by Charles Howard Hinton in his book A New Era of Thought, from the Greek τέσσερεις ἀκτίνες (téssereis aktínes, "four rays"), referring to the four lines from each vertex to other vertices.^{ [6]} In this publication, as well as some of Hinton's later work, the word was occasionally spelled "tessaract".
Geometry
The tesseract can be constructed in a number of ways. As a regular polytope with three cubes folded together around every edge, it has Schläfli symbol {4,3,3} with hyperoctahedral symmetry of order 384. Constructed as a 4D hyperprism made of two parallel cubes, it can be named as a composite Schläfli symbol {4,3} × { }, with symmetry order 96. As a 44 duoprism, a Cartesian product of two squares, it can be named by a composite Schläfli symbol {4}×{4}, with symmetry order 64. As an orthotope it can be represented by composite Schläfli symbol { } × { } × { } × { } or { }^{4}, with symmetry order 16.
Since each vertex of a tesseract is adjacent to four edges, the vertex figure of the tesseract is a regular tetrahedron. The dual polytope of the tesseract is called the regular hexadecachoron, or 16cell, with Schläfli symbol {3,3,4}, with which it can be combined to form the compound of tesseract and 16cell.
The standard tesseract in Euclidean 4space is given as the convex hull of the points (±1, ±1, ±1, ±1). That is, it consists of the points:
A tesseract is bounded by eight hyperplanes (x_{i} = ±1). Each pair of nonparallel hyperplanes intersects to form 24 square faces in a tesseract. Three cubes and three squares intersect at each edge. There are four cubes, six squares, and four edges meeting at every vertex. All in all, it consists of 8 cubes, 24 squares, 32 edges, and 16 vertices.
Projections to two dimensions
The construction of hypercubes can be imagined the following way:
 1dimensional: Two points A and B can be connected to become a line, giving a new line segment AB.
 2dimensional: Two parallel line segments AB and CD can be connected to become a square, with the corners marked as ABCD.
 3dimensional: Two parallel squares ABCD and EFGH can be connected to become a cube, with the corners marked as ABCDEFGH.
 4dimensional: Two parallel cubes ABCDEFGH and IJKLMNOP can be connected to become a tesseract, with the corners marked as ABCDEFGHIJKLMNOP.
It is possible to project tesseracts into three and twodimensional spaces, similarly to projecting a cube into twodimensional space.
Projections on the 2Dplane become more instructive by rearranging the positions of the projected vertices. In this fashion, one can obtain pictures that no longer reflect the spatial relationships within the tesseract, but which illustrate the connection structure of the vertices, such as in the following examples:
A tesseract is in principle obtained by combining two cubes. The scheme is similar to the construction of a cube from two squares: juxtapose two copies of the lowerdimensional cube and connect the corresponding vertices. Each edge of a tesseract is of the same length. This view is of interest when using tesseracts as the basis for a network topology to link multiple processors in parallel computing: the distance between two nodes is at most 4 and there are many different paths to allow weight balancing.
Parallel projections to 3 dimensions
The cellfirst parallel projection of the tesseract into threedimensional space has a cubical envelope. The nearest and farthest cells are projected onto the cube, and the remaining six cells are projected onto the six square faces of the cube.
The facefirst parallel projection of the tesseract into threedimensional space has a cuboidal envelope. Two pairs of cells project to the upper and lower halves of this envelope, and the four remaining cells project to the side faces.
The edgefirst parallel projection of the tesseract into threedimensional space has an envelope in the shape of a hexagonal prism. Six cells project onto rhombic prisms, which are laid out in the hexagonal prism in a way analogous to how the faces of the 3D cube project onto six rhombs in a hexagonal envelope under vertexfirst projection. The two remaining cells project onto the prism bases.
The vertexfirst parallel projection of the tesseract into threedimensional space has a rhombic dodecahedral envelope. Two vertices of the tesseract are projected to the origin. There are exactly two ways of dissecting a rhombic dodecahedron into four congruent rhombohedra, giving a total of eight possible rhombohedra, each a projected cube of the tesseract. This projection is also the one with maximal volume. One set of projection vectors are u=(1,1,1,1), v=(1,1,1,1), w=(1,1,1,1).
As a configuration
This configuration matrix represents the tesseract. The rows and columns correspond to vertices, edges, faces, and cells. The diagonal numbers say how many of each element occur in the whole tesseract. The nondiagonal numbers say how many of the column's element occur in or at the row's element.^{ [7]} For example, the 2 in the first column of the second row indicates that there are 2 vertices in (i.e., at the extremes of) each edge; the 4 in the second column of the first row indicates that 4 edges meet at each vertex.
Image gallery
The tesseract can be unfolded into eight cubes into 3D space, just as the cube can be unfolded into six squares into 2D space. An unfolding of a polytope is called a net. There are 261 distinct nets of the tesseract.^{ [8]} The unfoldings of the tesseract can be counted by mapping the nets to paired trees (a tree together with a perfect matching in its complement). 
Stereoscopic 3D projection of a tesseract (parallel view) 
Alternative projections
A 3D projection of a tesseract performing a double rotation about two orthogonal planes 
Perspective with hidden volume elimination. The red corner is the nearest in 4D and has 4 cubical cells meeting around it. 
The tetrahedron forms the convex hull of the tesseract's vertexcentered central projection. Four of 8 cubic cells are shown. The 16th vertex is projected to infinity and the four edges to it are not shown. 
Stereographic projection (Edges are projected onto the 3sphere) 
2D orthographic projections
Coxeter plane  B_{4}  B_{3} / D_{4} / A_{2}  B_{2} / D_{3} 

Graph  
Dihedral symmetry  [8]  [6]  [4] 
Coxeter plane  Other  F_{4}  A_{3} 
Graph  
Dihedral symmetry  [2]  [12/3]  [4] 
Radial equilateral symmetry
The long radius (center to vertex) of the tesseract is equal to its edge length; thus its diagonal through the center (vertex to opposite vertex) is 2 edge lengths. Only a few uniform polytopes have this property, including the fourdimensional tesseract and 24cell, the threedimensional cuboctahedron, and the twodimensional hexagon. In particular, the tesseract is the only hypercube with this property.^{ [9]} The longest vertextovertex diameter of an ndimensional hypercube of unit edge length is √n, so for the square it is √2, for the cube it is √3, and only for the tesseract it is √4, exactly 2 edge lengths.
Tessellation
The tesseract, like all hypercubes, tessellates Euclidean space. The selfdual tesseractic honeycomb consisting of 4 tesseracts around each face has Schläfli symbol {4,3,3,4}. Hence, the tesseract has a dihedral angle of 90°.^{ [10]}
The tesseract's radial equilateral symmetry makes its tessellation the unique regular bodycentered cubic lattice of equalsized spheres, in any number of dimensions.
The tesseract itself can be decomposed into smaller polytopes. For instance, it can be triangulated into 4dimensional simplices that share their vertices with the tesseract. It is known that there are 92487256 such triangulations^{ [11]} and that the least number of 4dimensional simplices in any of them is 16.^{ [12]}
Related complex polygon
Orthogonal  Perspective 

_{4}{4}_{2}, with 16 vertices and 8 4edges, with the 8 4edges shown here as 4 red and 4 blue squares. 
The regular complex polytope _{4}{4}_{2}, , in has a real representation as a tesseract or 44 duoprism in 4dimensional space. _{4}{4}_{2} has 16 vertices, and 8 4edges. Its symmetry is _{4}[4]_{2}, order 32. It also has a lower symmetry construction, , or _{4}{}×_{4}{}, with symmetry _{4}[2]_{4}, order 16. This is the symmetry if the red and blue 4edges are considered distinct.^{ [13]}
Related polytopes and honeycombs
As a uniform duoprism, the tesseract exists in a sequence of uniform duoprisms: {p}×{4}.
The regular tesseract, along with the 16cell, exists in a set of 15 uniform 4polytopes with the same symmetry. The tesseract {4,3,3} exists in a sequence of regular 4polytopes and honeycombs, {p,3,3} with tetrahedral vertex figures, {3,3}. The tesseract is also in a sequence of regular 4polytope and honeycombs, {4,3,p} with cubic cells.
In popular culture
Since their discovery, fourdimensional hypercubes have been a popular theme in art, architecture, and science fiction. Notable examples include:
 " And He Built a Crooked House", Robert Heinlein‘s 1940 science fiction story featuring a building in the form of a fourdimensional hypercube.^{ [14]} This and Martin Gardner's "The NoSided Professor," published in 1946, are among the first in science fiction to introduce readers to the Moebius band, the Klein bottle, and the hypercube (tesseract).
 Crucifixion (Corpus Hypercubus), a 1954 oil painting by Salvador Dalí featuring a fourdimensional hypercube unfolded into a threedimensional Latin cross.^{ [15]}
 The Grande Arche, a monument and building near Paris, France, completed in 1989. According to the monument's engineer, Erik Reitzel, the Grande Arche was designed to resemble the projection of a hypercube.^{ [16]}
 Fez, a video game where one plays a character who can see beyond the two dimensions other characters can see, and must use this ability to solve platforming puzzles. Features "Dot," a tesseract who helps you navigate the world and tells you how to use abilities, fitting the theme of seeing beyond human perception of known dimensional space.^{ [17]}
The word tesseract was later adopted for numerous other uses in popular culture, including as a plot device in works of science fiction, often with little or no connection to the fourdimensional hypercube of this article. See Tesseract (disambiguation).
See also
Notes
 ^ "The Tesseract  a 4dimensional cube". www.cuttheknot.org. Retrieved 20201109.
 ^ Matila Ghyka, The geometry of Art and Life (1977), p.68
 ^ This term can also mean a polycube made of four cubes
 ^ Elte, E. L. (1912). The Semiregular Polytopes of the Hyperspaces. Groningen: University of Groningen. ISBN 141817968X.
 ^ Coxeter 1973, pp. 122123, §7.2. illustration Fig 7.2C.
 ^ "Home : Oxford English Dictionary". Oed.com. Retrieved 21 January 2018.
 ^ Coxeter 1973, p. 12, §1.8 Configurations.
 ^ "Unfolding an 8cell". Unfolding.apperceptual.com. Retrieved 21 January 2018.
 ^ Strictly, the hypercubes of 0 dimensions (a point) and 1 dimension (a line segment) are also radially equilateral.
 ^ Coxeter 1973, p. 293.
 ^ Pournin, Lionel (2013), "The flipGraph of the 4dimensional cube is connected", Discrete & Computational Geometry, 49 (3): 511–530, arXiv: 1201.6543, doi: 10.1007/s004540139488y, MR 3038527, S2CID 30946324
 ^ Cottle, Richard W. (1982), "Minimal triangulation of the 4cube", Discrete Mathematics, 40: 25–29, doi: 10.1016/0012365X(82)901856, MR 0676709
 ^ Coxeter, H. S. M., Regular Complex Polytopes, second edition, Cambridge University Press, (1991).
 ^ Fowler, David (2010), "Mathematics in Science Fiction: Mathematics as Science Fiction", World Literature Today, 84 (3): 48–52, JSTOR 27871086
 ^ Kemp, Martin (1 January 1998), "Dali's dimensions", Nature, 391 (27): 27, Bibcode: 1998Natur.391...27K, doi: 10.1038/34063, S2CID 5317132
 ^ Ursyn, Anna (2016), "Knowledge Visualization and Visual Literacy in Science Education", Knowledge Visualization and Visual Literacy in Science Education, Information Science Reference, p. 91, ISBN 9781522504818
 ^ "Dot (Character)  Giant Bomb". Giant Bomb. Retrieved 21 January 2018.
References
 Coxeter, H.S.M. (1973). Regular Polytopes (3rd ed.). New York: Dover. pp. 122–123.
 F. Arthur Sherk, Peter McMullen, Anthony C. Thompson, Asia Ivic Weiss (1995) Kaleidoscopes: Selected Writings of H.S.M. Coxeter, WileyInterscience Publication
ISBN
9780471010036
[1]
 (Paper 22) H.S.M. Coxeter, Regular and Semi Regular Polytopes I, Mathematische Zeitschrift 46 (1940) 380407, MR 2,10]
 (Paper 23) H.S.M. Coxeter, Regular and SemiRegular Polytopes II, [Math. Zeit. 188 (1985) 559591]
 (Paper 24) H.S.M. Coxeter, Regular and SemiRegular Polytopes III, [Math. Zeit. 200 (1988) 345]
 John H. Conway, Heidi Burgiel, Chaim GoodmanStrass (2008) The Symmetries of Things, ISBN 9781568812205 (Chapter 26. pp. 409: Hemicubes: 1_{n1})
 T. Gosset (1900) On the Regular and SemiRegular Figures in Space of n Dimensions, Messenger of Mathematics, Macmillan.
 T. Proctor Hall (1893) "The projection of fourfold figures on a threeflat", American Journal of Mathematics 15:179–89.

Norman Johnson Uniform Polytopes, Manuscript (1991)
 N.W. Johnson: The Theory of Uniform Polytopes and Honeycombs, Ph.D. (1966)
 Victor Schlegel (1886) Ueber Projectionsmodelle der regelmässigen vierdimensionalen Körper, Waren.
External links
 Weisstein, Eric W. "Tesseract". MathWorld.
 Klitzing, Richard. "4D uniform polytopes (polychora) x4o3o3o  tes".
 The Tesseract Ray traced images with hidden surface elimination. This site provides a good description of methods of visualizing 4D solids.
 Der 8Zeller (8cell) Marco Möller's Regular polytopes in ℝ^{4} (German)
 WikiChoron: Tesseract
 HyperSolids is an open source program for the Apple Macintosh (Mac OS X and higher) which generates the five regular solids of threedimensional space and the six regular hypersolids of fourdimensional space.
 Hypercube 98 A Windows program that displays animated hypercubes, by Rudy Rucker
 ken perlin's home page A way to visualize hypercubes, by Ken Perlin
 Some Notes on the Fourth Dimension includes animated tutorials on several different aspects of the tesseract, by Davide P. Cervone
 Tesseract animation with hidden volume elimination
4polytopes 
