Sources and licences

Ballpark has 200 questions: 50 distances, 50 heights and lengths, 50 years, 50 populations. Every answer was checked against two independent sources on 2026-10-19, by an automated cross-check plus reading each page; the build refuses any answer whose sources disagree. The full list with answers and sources is on a separate page with spoilers.

Distances

Each distance is computed, not looked up: the shortest path over the Earth’s surface (the WGS84 ellipsoid, using Vincenty’s formula, tested against Karney’s GeographicLib) between two city points from Natural Earth 1:10m populated places, version 5.1.2 (public domain; terms). It is rounded to the nearest 10 km. As a second source, the same computation from the Wikidata coordinates of each city must agree within 15 km or 1.5%. City points mark a city centre, so other references can differ by a few kilometres. Made with Natural Earth.

Heights, lengths and years

Each value was checked against Wikidata (CC0) and at least one independent page: an encyclopedia article, an official site, a space agency fact sheet or a sport’s rule book. Where they define a value differently (with or without an antenna, the canal with or without its approach channels), the question either says exactly what is meant or was left out. Figures that change quickly or are disputed (river lengths, Aconcagua’s height, the depth of Lake Baikal, the height of Victoria Falls) are not used.

Populations

Population answers are World Bank estimates for mid-2024 (World Development Indicators, Population, total, SP.POP.TOTL, data updated 2026-10-08), rounded to three significant figures. Source: World Bank, World Development Indicators, Population, total (SP.POP.TOTL), 2024, CC BY 4.0. Figures rounded to 3 significant figures by Ballpark. Licence: CC BY 4.0. The second, independent source is the CIA World Factbook estimate for 2024, produced by the US Census Bureau (a US government work); the two must agree within 3%. The UN World Population Prospects 2024 figure is recorded as a reference. Countries whose figures disagree, or that are in conflict or disputed, are not included.

The comparisons

The “for scale” line under each answer compares it with another checked question (for example the Eiffel Tower or Paris to Rome), so it adds no unchecked number. Flight times assume a steady 900 km/h and driving times 100 km/h without stops; they are illustrations, not timetables. The explanations are written for Ballpark.

Font and artwork

Bricolage Grotesque, © The Bricolage Grotesque Project Authors, under the SIL Open Font License 1.1, served from this site. The mark, icons, number lines and sounds are original, made in code for Ballpark. There is no music.

Corrections

Spotted a mistake or a better source? Write to support@twindle.nl. A corrected question gets a new revision; rounds already played keep their scores.