{
  "title": "Eleven straight tunnels through the Earth",
  "description": "Eleven straight tunnels from 100 km to the 12,742 km diameter, one row each: depth at the middle, surface distance between the ends, top speed and one-way time in a uniform, frictionless Earth (closed form and numerical integration, with their difference), and the one-way time under a constant-gravity approximation (numerical integration). Constants from NASA's Earth Fact Sheet (radius 6371.000 km, surface gravity 9.820 m/s^2). Retrieved 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": [
    "NASA NSSDCA, Earth Fact Sheet (last updated 2024-11-15), volumetric mean radius 6371.000 km and surface gravity (mean) 9.820 m/s^2, https://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html"
  ],
  "method": "Compiled by Puzzles, Charts & Dilemmas from the data listed",
  "data_credit": [
    "NASA Earth Fact Sheet (radius and surface gravity)"
  ]
}