{
  "about": "Every source Light Floor uses, with its citation, location, retrieval date and rights. The vendored files ship with the page; the only other hosts the page contacts are the 32 AWS endpoints it times.",
  "sources": [
    {
      "id": "speed-of-light",
      "citation": "Bureau International des Poids et Mesures, The International System of Units (SI Brochure), 9th edition (2019), section 2.3.1: the speed of light in vacuum c = 299 792 458 m/s, exact",
      "url": "https://www.bipm.org/en/publications/si-brochure",
      "retrieved": "2026-10-08",
      "used": "src/engine/light.ts C_KM_S",
      "rights": "A defined constant; no rights apply."
    },
    {
      "id": "corning-smf28e-plus",
      "citation": "Corning SMF-28e+ Optical Fiber, Product Information PI1463 (June 2014): \"Effective Group Index of Refraction (Neff) 1550 nm: 1.4682\"",
      "url": "https://img-en.fs.com/file/datasheet/corning-smf-28eplus-33175.pdf",
      "retrieved": "2026-10-08",
      "note": "corning.com answered 403 to every request for its own copy, so the figure was read from this distributor's unaltered copy of PI1463.",
      "used": "src/engine/light.ts GROUP_INDEX; the glass floor and the 68.11 % glass ceiling",
      "rights": "A published specification figure, quoted. Corning is not affiliated with Light Floor; no Corning mark is used."
    },
    {
      "id": "geonames-cities15000",
      "citation": "GeoNames, cities15000: all cities with a population of 15,000 or more",
      "url": "https://download.geonames.org/export/dump/cities15000.zip",
      "retrieved": "2026-10-09 (UTC)",
      "vendored": "public/cities.json (the picker, 34,156 places) and src/data/places.json (the region stand-in cities, and Chicago, Aurora and Carteret), by scripts/fetch-geonames.mjs",
      "rights": "Creative Commons Attribution 4.0. Credited in every page footer."
    },
    {
      "id": "un-wup-2025",
      "citation": "United Nations, Department of Economic and Social Affairs, Population Division, World Urbanization Prospects: The 2025 Revision, cities database (Degree of Urbanisation definition)",
      "url": "https://population.un.org/wup/assets/Download/Cities/WUP2025-DB-DEGURBA-Cities-Population-Surface-Data.csv.gz",
      "retrieved": "2026-10-09",
      "vendored": "src/data/places.json metros (79 cities, each with its WUP name, code, 2025 rank and population-weighted centre), by scripts/fetch-wup.mjs",
      "rule": "The 60 largest cities in World Urbanization Prospects 2025 by mid-2025 population (Degree of Urbanisation definition), plus the largest WUP city within 60 km of each timed AWS region's point, in the same country: 79 in all. Pages: 3,081 pairs.",
      "admissions": [
        "WUP draws a city as one dense, contiguous built-up area (at least 1,500 people per km² and 50,000 people), not by its legal boundary, so Hajipur, India, counts as one city of 9.9 million and ranks 34th.",
        "us-west-2 (Oregon) has no city on the list: its stand-in, Bend, is below WUP's threshold, and the nearest WUP city, Eugene, is 140 km away.",
        "Amsterdam is not on the list: it is neither among the 60 largest nor the city of a timed AWS region.",
        "Replaced the first day's list (the 60 most populous GeoNames cities, city proper) on 2026-10-09; pairs that survived kept their URLs."
      ],
      "used": "The floor pages: the distance between two cities is measured between their WUP population-weighted centres.",
      "rights": "Creative Commons Attribution 3.0 IGO. Credited in every page footer."
    },
    {
      "id": "natural-earth-land",
      "citation": "Natural Earth, 1:110m physical vectors, land",
      "url": "https://www.naturalearthdata.com/downloads/110m-physical-vectors/",
      "retrieved": "2026-10-06",
      "vendored": "public/land.json, copied unchanged from github.com/MeeshaBear1/besselian public/land.json (coordinates in tenths of a degree, 128 rings)",
      "rights": "Public domain."
    },
    {
      "id": "aws-regions",
      "citation": "Amazon Web Services, DynamoDB service endpoints, one per region: https://dynamodb.<region>.amazonaws.com/ping",
      "url": "https://docs.aws.amazon.com/general/latest/gr/ddb.html",
      "retrieved": "2026-10-08",
      "used": "src/data/places.json regions; src/measure.ts; vercel.json connect-src, one host per region",
      "dropped": "me-south-1 (Bahrain) is left out: its endpoint did not answer from curl or from a browser on 2026-10-08.",
      "placement": "Each region sits at its city's GeoNames point (the floor pages use WUP centres instead) (±50 km, ±0.33 ms on a round trip). Regions named for a state or a country sit at a stand-in city with a wider radius, listed with each region's radiusKm in src/data/places.json and on the page under The Working.",
      "rights": "The endpoints are timed, never read: each request is no-cors and its answer stays opaque. Light Floor is not affiliated with Amazon Web Services; no AWS mark is used."
    },
    {
      "id": "vercel-ip-headers",
      "citation": "Vercel, request headers: x-vercel-ip-latitude, x-vercel-ip-longitude, x-vercel-ip-city, x-vercel-ip-country",
      "url": "https://vercel.com/docs/headers/request-headers",
      "retrieved": "2026-10-08",
      "used": "api/where.ts, which returns them to the page and stores nothing"
    },
    {
      "id": "geographiclib",
      "citation": "C. F. F. Karney, \"Algorithms for geodesics\", Journal of Geodesy 87 (2013) 43–55; GeographicLib for Python",
      "url": "https://geographiclib.sourceforge.io/",
      "retrieved": "2026-10-08",
      "used": "test/fixtures/geographiclib.json: ten WGS84 distances the engine's Lambert formula is checked against",
      "rights": "MIT licence. Used to make the fixtures only; not shipped."
    },
    {
      "id": "equal-earth",
      "citation": "B. Šavrič, T. Patterson and B. Jenny, \"The Equal Earth map projection\", International Journal of Geographical Information Science 33 (2019) 454–465",
      "url": "https://doi.org/10.1080/13658816.2018.1504949",
      "retrieved": "2026-10-08",
      "used": "src/engine/geo.ts equalEarth"
    },
    {
      "id": "lightwave-spread",
      "citation": "S. Hardy, \"Spread Networks to debut low latency New York to Chicago dark fiber route\", Lightwave, 22 June 2010",
      "url": "https://www.lightwaveonline.com/network-design/article/16671350/spread-networks-to-debut-low-latency-new-york-to-chicago-dark-fiber-route",
      "retrieved": "2026-10-08",
      "used": "The Straight Wire: 825 fiber miles, 13.33 ms round trip"
    },
    {
      "id": "laughlin-aguirre-grundfest",
      "citation": "G. Laughlin, A. Aguirre and J. Grundfest, \"Information Transmission Between Financial Markets in Chicago and New York\", The Financial Review 49 (2014) 283–312",
      "url": "https://arxiv.org/abs/1302.5966",
      "retrieved": "2026-10-08",
      "used": "The Straight Wire: Spread Networks at about 6.65 ms one way; microwave links at 4.2 to 5.2 ms; the 3.93 ms floor from Aurora, Illinois, to Carteret, New Jersey; the cost of about $300 million, which the paper attributes to C. Steiner, \"Wall Street's Speed War\", Forbes, 27 September 2010"
    },
    {
      "id": "fonts",
      "citation": "Big Shoulders (Patric King), Albert Sans (Andreas Rasmussen), Reddit Mono (Reddit, Inc.), via Fontsource",
      "url": "https://fontsource.org/",
      "retrieved": "2026-10-08",
      "vendored": "@fontsource-variable packages, bundled and served from this host",
      "rights": "SIL Open Font License 1.1."
    }
  ]
}