Non Euclidean Geometry

Non-Euclidean Geometry refers to the branch of mathematics that deals with the study of geometry on Curved Surfaces. It is a different way of studying shapes compared to what Euclid, an ancient mathematician, taught. There are two main types: hyperbolic and elliptic geometries. In these, we change the working of lines which gives us different shapes than usual. Hyperbolic shapes have a saddle-like curve, and elliptic shapes have a round curve.

In this article, we will understand the various concepts related to non-euclidean geometry like definition, the historical background of non-euclidean geometry, its principles, its application, and the types of noon-euclidean geometry.

What is Non-Euclidean Geometry?

Non-Euclidean geometry is a branch of geometry that explores geometrical systems that differ from classical Euclidean geometry, which is based on the postulates of the ancient Greek mathematician Euclid. In Non-Euclidean geometry, these traditional postulates are altered or replaced, leading to different mathematical consequences.

Non-Euclidean Geometry deals with hyperbolic and spherical surfaces and traditionally there is no study of straight lines. In other words, we can say that Non-Euclidean Geometry deals with curved surfaces.

Definition of Non-Euclidean Geometry

Non-Euclidean geometry is a branch of geometry that explores geometric systems deviating from classical Euclidean geometry. It includes hyperbolic and elliptic geometries, where alterations to Euclid’s parallel postulate lead to distinct geometric properties and theorems.

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History of Non-Euclidean Geometry

Euclidean geometry was named after ancient mathematician Euclid and it was the norm until the 19th century. The debate on Non-Euclidean geometry started after Euclid’s book, Elements. Euclid’s Fifth Postulate had challenges. Mathematicians like Ibn al-Haytham, Omar Khayyám, and Giovanni Girolamo Saccheri attempted proofs but faced difficulties. Khayyam and al-Tusi tried non-Euclidean geometry but had flawed proofs.

In the 18th century, Saccheri unintentionally discovered non-Euclidean geometry. In the 19th century, Johann Lambert worked on the same problem but didn’t publish. Bolyai suggested the universe might follow Euclidean or non-Euclidean geometry. In 1854, Riemann founded Riemannian geometry, expanding to non-Euclidean geometries.

Evolution of Non-Euclidean Geometry

Following aspects led to the evolution of non-euclidean geometry

• Different formulations emerge, like Playfair’s axiom, to describe relationships between lines and angles.
• Mathematicians like Khayyam, al-Tusi, and Saccheri attempted to prove or derive non-Euclidean principles, but initial efforts contained flaws.
• Saccheri’s exploration using a quadrilateral unintentionally led to the discovery of non-Euclidean geometry.
• Lambert’s work with quadrilaterals and acute angles contributed to non-Euclidean insights but remained unpublished.
• Lobachevsky and Bolyai independently published treatises on hyperbolic geometry, a form of non-Euclidean geometry.
• Bolyai suggests that the physical universe might follow either Euclidean or non-Euclidean geometry, leaving the determination to physical sciences.
• In 1854, Bernhard Riemann introduces Riemannian geometry, laying the groundwork for non-Euclidean geometries with concepts like manifolds, Riemannian metric, and curvature.
• Beltrami, in 1868, applies Riemann’s geometry to spaces with negative curvature, further expanding non-Euclidean possibilities.

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Non-Euclidean Geometry Postulates

Non Euclidean Geometry is Geometry on curved spaces. Following are the principles of Non-Euclidean Geometry:

• Non-Euclidean geometry rejects Euclid’s Fifth Postulate, stating that parallel lines never meet.
• Non-Eulidean Geometry uses the concept of Geodesics to represent shortest distance between two points on curved surfaces
• In Non-Euclidean Geometry, the sum of angle is not necessarily equal to 180°
• All points on the sphere’s surface are assumed to be at the same distance from the sphere’s centre.
• Angle between any two points on Sphere’s surface is less than 180°

Types of Non-Euclidean Geometry 

There are two types of figures classified based on Euclid’s parallel postulate. Figures that deviate from satisfying the parallel postulate are categorized as non-Euclidean. The main types of non-Euclidean figures are the hyperbola and ellipse. Non-Euclidean geometry is further divided based on the shapes of these figures into two branches:

• Hyperbolic Geometry
• Elliptical Geometry

Hyperbolic Geometry

Hyperbolic Geometry, a departure from Euclidean principles, was first conceptualized within Euclid’s postulates. It was established that hyperbolic geometries differ only in scale.

• In the mid-19th century, it was demonstrated that hyperbolic surfaces must possess constant negative curvature.
• Eugenio Beltrami’s pseudosphere, described in 1868, showed constant negative curvature but wasn’t a complete model for hyperbolic geometry.
• David Hilbert, in 1901, showed the impossibility of defining a complete hyperbolic surface using real analytic functions.
• However, Nicolaas Kuiper later proved the existence of such a surface in 1955, and William Thurston provided a construction in the 1970s.
• Three models were Klein-Beltrami, Poincaré disk, and Poincaré upper half-plane, these models helped in visualizing hyperbolic geometry despite some distortion.

Elliptic Geometry

Elliptic Geometry, another departure from Euclidean geometry, was first explored within the framework of Euclid’s postulates. Unlike hyperbolic geometry, elliptic geometries differ only in scale.

• In the mid-19th century, it was established that elliptic surfaces must have constant positive curvature.
• Eugenio Beltrami, in 1868, described a surface called the pseudosphere, displaying constant positive curvature.
• However, this pseudosphere isn’t a complete model for elliptic geometry, as straight lines on it may intersect themselves and can’t be extended beyond a certain point.
• Unlike hyperbolic and Euclidean geometry, elliptic geometry doesn’t have a flat model that can be represented on a plane without distortion.

Primarily only Hyperbolic and Elliptical Geometry are types of Non-Euclidean Geometry but Spherical Geometry also forms a part of Non-Euclidean Geometry. Hence, we will have a look on Spherical Geometry.

Spherical Geometry

Spherical Geometry is a non-Euclidean geometry that focuses on the surface of a sphere. In this geometry, space is represented by the curved surface of a sphere, which exhibits constant positive curvature.

• Unlike Euclidean geometry, spherical geometry lacks parallel lines, and any two great circles on a sphere intersect at two points.
• Spherical triangles, formed by great circle arcs, replace the traditional triangles of Euclidean geometry, with their angles summing to more than 180 degrees.
• Distances on a sphere are measured along great circle arcs, making the shortest distance between two points along a segment of a great circle.
• Spherical geometry finds practical applications in navigation, astronomy, and geography, particularly when considering the Earth’s surface as a sphere for calculations.

Applications of Non Euclidean Geometry

Some applications of non-euclidean geometry are:

• Relativity Theory: Non-Euclidean geometries, particularly hyperbolic geometry, play a crucial role in Einstein’s theory of general relativity, providing a framework for understanding the curvature of spacetime caused by gravity.

• Navigation: Spherical geometry, a type of non-Euclidean geometry, is employed in navigation, especially for calculating distances and directions on the Earth’s surface, which is approximately spherical.

• Computer Graphics: Non-Euclidean geometries are used in computer graphics for modeling curved surfaces and spaces, allowing more realistic representations of three-dimensional objects.

• Topology: Non-Euclidean concepts contribute to the field of topology, helping mathematicians study properties that remain unchanged under continuous deformations.

• Cosmology: The geometry of the universe, as described by non-Euclidean principles, is explored in cosmology. Understanding the curvature of space contributes to theories about the large-scale structure of the cosmos.

• Art and Design: Concepts from non-Euclidean geometries, especially hyperbolic geometry, are utilized in art and design for creating visually engaging and intricate patterns, such as Escher’s famous artworks.

• Physics Simulations: Non-Euclidean geometries are employed in physics simulations, enabling accurate modeling of phenomena that involve curved spaces, like the behavior of light near massive objects.

• Robotics and Path Planning: Non-Euclidean geometries are used in robotics for path planning, helping robots navigate efficiently in environments where traditional Euclidean geometry may not be suitable.

Difference Between Non-Euclidean and Euclidean Geometry

The difference between non-euclidean and euclidean geometry are as follows:

Euclidean vs Non-Euclidean Geometry
Aspect	Non-Euclidean	Euclidean
Parallel Postulate	Exactly one parallel line through a point not on a line.	May have zero or multiple parallel lines through a point.
Space Curvature	Flat, zero curvature.	Curvature may be positive (elliptic) or negative (hyperbolic).
Sum of Angles in a Triangle	Always equals 180 degrees.	May be greater than or less than 180 degrees.
Surface Shapes	Planes, circles, and straight lines.	Hyperbolas, ellipses, and curved lines.
Geometry Foundation	Based on Euclid’s postulates.	Altered or replaced postulates, challenging Euclidean norms.
Applications	Traditional geometry used in most everyday contexts.	Relevant in non-traditional spaces, like curved surfaces.

Non Euclidean Geometry – FAQs

What is Meaning of Non Eucledian Geometry?

Non-Euclidean geometry refers to a set of geometrical systems that do not adhere to the postulates of Euclidean geometry, which is the classical geometry developed by the ancient Greek mathematician Euclid.

Is Earth Non Eucledian?

No, for practical purposes, Earth is considered to follow Euclidean geometry at small scales. However, on a global scale the space around the earth is considered to be Non-Euclidean

What is difference between Eucledian and Non Eucledian Geometry?

The Difference between Eclidean and Non-Euclidean Geometry is that Euclid Geometry follows postutalets of Euclid and deals with plane surfaces while Non-Euclidean Geometry deals with curved spaces

Is Universe Non-Eucledian?

The exact shape of Universe is not defibed till date. It is currently unknown if the universe is simply connected like euclidean space or multiply connected like a torus. This is the reason Universe is neither considered to be Eucledian or Non-Eucleadian.

Who is Founder of Non-Euclidean Geometry?

Bolayi Janos of Hungary and Lobachevsky are considered founder of Non-Euclidean Geometry

Who is Father of Geometry?

Euclid is regarded as Father of Geometry

What is Geodesics in Non-Euclidean Geometry?

In Non-Euclidean Geometry, Geodesics the shortest distance between two points on curved surface. It is analogous to the straight line in Euclidean Geometry