{
  "title": "How GPS Finds You",
  "description": "Your phone finds you in seconds, anywhere on Earth, using satellites, atomic clocks and the speed of light. A short, clear explainer on the timing trick behind GPS, and why Einstein is part of it.",
  "duration_seconds": 82.43,
  "chapters": [
    {
      "start_seconds": 0.0,
      "title": "How GPS finds you"
    },
    {
      "start_seconds": 8.88,
      "title": "Satellites that shout the time"
    },
    {
      "start_seconds": 22.52,
      "title": "Timing is the measuring tape"
    },
    {
      "start_seconds": 38.03,
      "title": "Spheres, then a point"
    },
    {
      "start_seconds": 50.58,
      "title": "Why a fourth satellite?"
    },
    {
      "start_seconds": 64.41,
      "title": "It is a clock, not a map"
    }
  ],
  "sources": [
    "How GPS works: satellites, timing and location, ReadKernel",
    "How GPS Works: The Physics of Satellite Navigation, World of Physics",
    "How GPS Uses Atomic Time, TodaysDateAndTime",
    "Global Positioning System Becomes Operational, EBSCO"
  ]
}