Sources and licences

Ballpark has 748 questions: 100 distances, 189 heights and lengths, 200 years, 97 populations, 128 areas, 34 “how many” counts. 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.

Areas

Two kinds of area question, and each one says which it asks for. Total area (land plus lakes and rivers, never the sea) comes from the United Nations Statistics Division (UNdata country profiles) and the CIA World Factbook (through an independent archive of its historical data), read on 21 October 2026; the two must agree within 1%, and where they differ slightly the answer is rounded to a precision both share. Each total is also checked against the World Bank surface area or Wikidata (within 2%). The two Great Lakes use the US Environmental Protection Agency with a second reference. Land area questions use the World Bank figure (World Development Indicators, AG.LND.TOTL.K2, data updated 2026-10-08, CC BY 4.0), rounded to three significant figures. They are only asked for countries where the Wikidata total area is within 3% of it and an area computed from Natural Earth’s country borders within 10%, so there is no doubt about what is included. Countries with disputed borders are left out. Source: World Bank, World Development Indicators, Land area (AG.LND.TOTL.K2) and Surface area (AG.SRF.TOTL.K2), CC BY 4.0. Land areas rounded to 3 significant figures by Ballpark.

“How many” and the newer questions

The counts and the questions added on 22 October 2026 (sports dimensions, aircraft and spacecraft, moons, opera premieres, first editions, element discoveries, space milestones and independence dates) were researched for Ballpark from two independent publishers each (museums, space agencies, governing bodies, national and international bodies, encyclopedias and reference works), with a short quotation of each that states the figure; an automated check confirms every quotation states the answer. Where sources define a figure differently, the question says exactly what is meant, or it was left out.

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 usually the CIA World Factbook estimate for 2024, produced by the US Census Bureau (a US government work); the two must agree within 3%. For some places added later the second source is the official national figure instead: Eurostat's average population for 2024 (source: Eurostat, demo_gind; within 1%) or the national statistics office's own published figure (linked on the question; within 3%), and then the Factbook must still be within 7%. The UN World Population Prospects 2024 figure is recorded as a reference. Places 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, Paris to Rome, Switzerland or a chessboard), so it adds no unchecked number. A word like “about twice” is only used when it is within 12% of the true ratio; otherwise the line gives the ratio as a number. The side of a square of the same area is plain arithmetic. 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.