"Geometrical Investigations on the Theory of Parallels"

"Geometrical Investigations on the Theory of Parallels" is a work by mathematician Nikolai Lobachevsky, published in the early 19th century. It explores non-Euclidean geometry, particularly the concept that through a point not on a given line, more than one parallel line can be drawn. This challenged the long-held belief stemming from Euclidean geometry that only one parallel line could exist. Lobachevsky's ideas opened new avenues in mathematics, shaping the understanding of geometry and influencing the development of modern mathematics, physics, and even theories of space and time.