Fourth Dimension / Non-euclidean Geometry

Four-dimensional space (4-D) extends three-dimensional space (3-D) by adding an additional dimension to describe an object. The extra dimension is normally time, but in some speculative mathematical conceptions refers to an extra 4th dimension of space which is used to describe object sizes and locations.

The ordinary 3-D Euclidean concept of space aligns with everyday spatial experiences, while higher spatial dimensions were explored in the 19th century. Charles Howard Hinton popularised 4-D space in 1880, illustrating a “four-dimensional cube” by connecting two 3-D cubes in 2-D space, with lines representing a direction in the unseen fourth dimension.

Higher-dimensional spaces underlie significant mathematical and physical theories, including Einstein’s non-Euclidean spacetime in 4-D through his General Theory of Relativity (1915), which postulates that space and time are not separate entities, but rather interwoven into a single, unified four-dimensional continuum known as spacetime. (whereby time is postulated as the ‘4th’ dimension). 


Refers to the mathematical study of geometric shapes and concepts in a space with “n” independent coordinates, where “n” can be any positive integer, essentially allowing for more than the three spatial dimensions we experience (length, width, height); this means you can define points, lines, planes, and more complex shapes using “n” values to represent their position in this higher dimensional space. 

Principles 

  • Conceptualisation: While we can’t readily visualise spaces beyond 3-D, the mathematical framework for higher dimensions is built by extending the concepts of points, lines, and planes using additional coordinates. 
  • Coordinate system: Each point in an n-dimensional space is defined by a set of “n” coordinates, like (x1, x2, …, xn). 
  • Applications: N-dimensional geometry is crucial in fields like machine learning, data analysis, physics, and computer graphics where complex datasets might require representation in higher-dimensional spaces. 

Examples

  • Hyperplane: A “flat” surface in n-dimensional space, similar to a plane or flat surface in 3-D. 
  • Hypercube: An n-dimensional cube, where each side is perpendicular to all others. 
  • Hypersphere: An n-dimensional sphere.

Concepts

  • Vector operations: Addition, subtraction, dot product, and other vector operations can be extended to n-dimensional spaces. 
  • Distance metrics: Defining how to measure distance between points in n-dimensional space, like the Euclidean distance. 
  • Linear transformations: Operations like rotations and scaling can be performed.

Non-Euclidean geometry is any geometry that does not follow the rules of Euclid’s geometry. 

Examples of Non-Euclidean geometry

  • Spherical geometry: Spherical geometry allows triangles to have angle sums greater than 180° with no parallel lines. 
  • Hyperbolic geometry: Hyperbolic geometry rejects Euclid’s fifth postulate, allowing multiple parallels through a point not on a line, and the sum of a triangle’s angles is less than 180°. 

Non-Euclidean geometry in real life 

  • Einstein’s general relativity employs non-Euclidean geometry to describe spacetime curvature. 
  • The surface of a sphere is non-Euclidean, yet Euclidean geometry approximates it locally, as seen in small triangles where the angle sum approaches 180°. 

Maurits Cornelis Escher (1898 – 1972) was a Dutch graphic artist who made woodcuts, lithographs, and mezzotints, many of which were inspired by mathematics. His work features mathematical objects and operations, including impossible objects, explorations of infinity, reflection, symmetry, perspective, truncated and stellated polyhedra, hyperbolic geometry, and tessellations.

Hyperbolic perspective is a type of non-Euclidean and mathematical perspective investigated by famous mathematician Donald Coxeter and artist M.C. Escher.