Sources

How entries are made

The borders are scholars' work. Every shape on the map comes from the datasets listed below — Cliopatria and, for the German states, Historical Basemaps. No AI draws or alters them.

The text is written with AI. The glossary articles and the short territory descriptions in the map were researched and drafted by an AI research assistant, working from the sources named on each entry: for most, the subject's English Wikipedia article; for some, reference works such as Britannica, Encyclopaedia Iranica and World History Encyclopedia.

What the build checks. Each entry is matched to the territory it describes on the map, and the match is verified before a page is published. Dates the research does not state are never filled in — the page says what the map draws instead. Passages the research itself marked as unverified are held back rather than published.

What it does not do. The entries are not written or reviewed by professional historians, and not every sentence has been checked by a person. AI can get dates, names and details wrong. Treat an entry as a well-sourced starting point, follow its sources for anything that matters, and if you find a mistake, tell us at hello@theworldthroughtime.com — corrections go into the research and are republished.

The borders on the map

• Cliopatria v0.12 CC-BY-4.0

  Seshat Global History Databank

  Roughly 14,000 dated polygons covering the whole world from AD 1. Every territory on the map comes from here unless the panel says otherwise.

• Historical Basemaps GPL-3.0

  André Ourednik

  Fixed-year snapshots, used only for the optional German states overlay between 1715 and 1814, where Cliopatria draws a single Holy Roman Empire blob.

• Natural Earth 1:110m land Public domain

  Natural Earth

  The coastline silhouette drawn behind the territories in equal-area mode.

• Natural Earth 1:50m shaded relief Public domain

  Natural Earth

  The optional relief under the Mercator projection, reprojected and cut into tiles served from this site rather than a third-party tile service.

Code and type

• Leaflet 1.9.4 BSD-2-Clause

  Volodymyr Agafonkin and contributors

  Drives the Mercator backend only, served from this site rather than a CDN. The equal-area backend is plain SVG with no dependencies.

• Equal Earth projection Published method

  Bojan Šavrič, Tom Patterson and Bernhard Jenny (2018)

  The default projection. Implemented directly from the paper's coefficients, so areas on screen are true to areas on the ground.

• Geist and Geist Mono SIL Open Font License 1.1

  Vercel

  Self-hosted, so no request ever leaves the page for a font.

Method

• Douglas–Peucker simplification Published method

  David Douglas and Thomas Peucker (1973)

  Reduces the source geometry to a 0.25° tolerance (~28 km). The source's own point spacing is ~41 km, so nothing visible is lost.

• Sutherland–Hodgman clipping Published method

  Ivan Sutherland and Gary Hodgman (1974)

  Clips polygons to the map's bounding rectangle at build time.

Reference works cited in the glossary

Most entries are anchored on their subject's English Wikipedia article; some also draw on independent reference works — Britannica, Encyclopaedia Iranica, World History Encyclopedia, UNESCO, university repositories and specialist works. Some regional research files cite their sources once for the whole region rather than per entry. Everything consulted is listed below, grouped by publisher.