1783: Leonhard Euler dies in St. Petersburg

On 18 September 1783 the Swiss mathematician Leonhard Euler collapsed from a brain haemorrhage in St. Petersburg and died a few hours later, aged 76. He had already published more than 500 works and left behind enough manuscripts to keep printers busy for decades. Euler’s career spanned pure mathematics, mechanics, optics and astronomy, yet almost every modern computational idea can trace a line back to him.

The most direct bridge to artificial intelligence is graph theory. In 1736 Euler solved the Seven Bridges of Königsberg puzzle by inventing the abstract notion of a graph—vertices linked by edges. That single insight became the language of networks. Today’s knowledge graphs, social-network analysis, shortest-path search and the connectivity patterns inside neural networks all descend from Euler’s simple diagram of the Pregel river.

Equally pervasive is his mathematical notation. The symbols f(x), e, i, Σ and the modern concept of a function itself are Euler’s gifts. Machine-learning papers are written in this vocabulary; every loss function, activation and gradient is expressed with tools he standardised. His systematic development of calculus and the calculus of variations supplied the analytic machinery that later became gradient descent, backpropagation and variational inference—the optimisation engines of contemporary AI.

Euler also explored infinite series, continued fractions and early generating functions. These techniques reappear in the analysis of algorithms, in the theory of formal languages and in the probabilistic models that power large language models. Even the numerical methods used to train neural nets on GPUs rest on Euler’s pioneering work on differential equations and discrete approximations.

When an AI system embeds words in a high-dimensional space, traverses a knowledge graph or minimises a loss landscape, it is walking paths first cleared in the eighteenth century. Euler never imagined electronic computers, yet the intellectual scaffolding of artificial intelligence is unmistakably his.