{
  "title": "Gravity train data card",
  "description": "Data card for the gravity train page: name, alternative name, type, earliest text read, how the numbers were checked and related entries, with the source for each field that has one. Compiled 2026-10-31. License CC BY 4.0.",
  "license": "CC BY 4.0",
  "license_url": "https://creativecommons.org/licenses/by/4.0/",
  "creator": "Puzzles, Charts & Dilemmas",
  "page": "https://puzzleschartsanddilemmas.com/thought-experiments/gravity-train/",
  "derived_from": [
    "Lewis Carroll, Sylvie and Bruno Concluded (preface dated Christmas 1893), chapter 7, Project Gutenberg ebook 48795 (public domain), https://www.gutenberg.org/ebooks/48795",
    "Alexander R. Klotz, The Gravity Tunnel in a Non-Uniform Earth, arXiv:1308.1342v1 (2013 preprint), figures reported only, https://arxiv.org/abs/1308.1342"
  ],
  "method": "Compiled by Puzzles, Charts & Dilemmas from the data listed"
}