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1823-1840 CEReputable source · 2 sourcesWell documented

Bolyai and Lobachevsky Discover Geometry Without Euclid's Fifth Postulate

Two mathematicians working independently invent a strange new world where more than one parallel line can pass through a point

On the timeline · around 1823-1840 CE · Modern MathematicsThe Scientific RevolutionModern MathematicsBolyai and Lobachevsky Discover Geometry Without Euclid's Fifth Postulate1725175017751800182518501875

Quick facts

Gauss's private conclusion
By 1817, kept unpublished
Bolyai's publication
1825, 24-page appendix
Lobachevsky's publications
Russian 1829; French 1837
Later application
Mathematical basis for Einstein's general relativity

What happened

Euclid's fifth postulate, the claim that exactly one line parallel to a given line can be drawn through a point not on it, had frustrated mathematicians for two thousand years; the mathematician d'Alembert called the state of the problem in 1767 the scandal of elementary geometry. Carl Friedrich Gauss privately concluded by 1817 that the fifth postulate was logically independent of Euclid's other assumptions and worked out consequences of a geometry with multiple parallels, but never published this work, keeping it a secret, writing in 1813 that in the theory of parallels we are even now not further than Euclid and calling it a shameful part of mathematics. Janos Bolyai, working independently in Hungary, wrote to his father in 1823 that he had discovered things so wonderful that he was astounded, and that out of nothing he had created a strange new world, publishing his results in 1825 as a 24-page appendix to his father's book. Nikolai Lobachevsky in Russia published the same essential idea, that more than one line parallel to a given line can pass through a point not on it, in Russian in 1829 and in French, reaching a wider audience, in 1837.

Why it matters

Non-Euclidean geometry proved that Euclid's parallel postulate was not a necessary truth but one possible choice among several consistent alternatives, undermining two thousand years of assumption that Euclidean geometry described the only possible geometric universe. The discovery, made independently by at least three mathematicians within roughly a decade of each other, later provided exactly the mathematical framework Einstein needed for general relativity, which describes gravity using a non-Euclidean, curved geometry of spacetime.

How we know

Bolyai's 1825 appendix and Lobachevsky's 1829 and 1837 publications survive as printed texts, and Gauss's private correspondence and unpublished notes, preserved and later studied by historians, independently confirm he had reached similar conclusions years earlier without publishing them.

Sources

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Part of a timelineHistory of Mathematics26 events · A number system built for taxes, a theorem older than the man it's named for, a proof too long for a margin, and an infinity too big to countView all →
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