{
  "description": "Public-domain historical images for the general relativity textbook. License rationale checked against Commons description pages; public-domain scope reflects stated jurisdictions.",
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    {
      "id": "einstein-1921",
      "title": "Albert Einstein in Vienna, 1921",
      "author": "Ferdinand Schmutzer (1870–1928)",
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      "upstream_source_url": "http://www.bhm.ch/de/news_04a.cfm?bid=4&jahr=2006",
      "license": "Public domain",
      "license_rationale": "Commons marks this photograph public domain in Austria and life-plus-95 jurisdictions because Schmutzer died in 1928. Its US rationale is 17 USC 303 for a work not published before 2003 by an author who died before 1956. Commons also records a keep decision on the copyright discussion.",
      "source_modifications": "Commons current file includes Quibik noise and scanning-defect reduction (2012).",
      "alt": "Albert Einstein standing beside a chalkboard in Vienna in 1921.",
      "file": "einstein-1921.jpg",
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      "verified_date": "2026-09-08",
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      "id": "newton-1689",
      "title": "Portrait of Sir Isaac Newton",
      "author": "Godfrey Kneller (1646–1723)",
      "date": "1689",
      "source_url": "https://commons.wikimedia.org/wiki/File:Portrait_of_Sir_Isaac_Newton,_1689.jpg",
      "direct_image_url": "https://upload.wikimedia.org/wikipedia/commons/3/3b/Portrait_of_Sir_Isaac_Newton%2C_1689.jpg",
      "upstream_source_url": "https://exhibitions.lib.cam.ac.uk/linesofthought/artifacts/newton-by-kneller/",
      "license": "Public domain; PD-Art (PD-old-auto-expired)",
      "license_rationale": "Commons marks the painting public domain because Kneller died in 1723, and marks it public domain in the US as published before 1931. Commons treats the faithful photographic reproduction of this two-dimensional public-domain work as public domain.",
      "source_modifications": "Commons current file crops caption and edges from the Cambridge reproduction (2022).",
      "alt": "Godfrey Kneller’s 1689 painted portrait of Isaac Newton.",
      "file": "newton-1689.jpg",
      "license_url": "https://creativecommons.org/publicdomain/mark/1.0/",
      "verified_date": "2026-09-08",
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      "id": "principia-1687",
      "title": "Philosophiae Naturalis Principia Mathematica, first-edition title page",
      "author": "Isaac Newton (1643–1727)",
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      "license": "Public domain; PD-old / Public Domain Mark",
      "license_rationale": "Commons explicitly marks this 1687 work public domain in countries with terms of life plus 100 years or fewer. The page lacks a separate US tag, but the printed title page was published in 1687, far earlier than the US public-domain cutoff.",
      "source_modifications": "Faithful color scan from University of Strasbourg; no further source edits stated.",
      "alt": "Title page of Newton’s 1687 first edition of Principia Mathematica.",
      "file": "principia-1687.jpg",
      "license_url": "https://creativecommons.org/publicdomain/mark/1.0/",
      "verified_date": "2026-09-08",
      "modifications": "Proportionally resized to maximum dimension 1400 pixels; JPEG recompressed at quality 85 with macOS sips. No cropping or content alterations.",
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    {
      "id": "einstein-gr-1916",
      "title": "Die Grundlage der allgemeinen Relativitätstheorie, 1916 separate-edition title page",
      "author": "Albert Einstein (1879–1955)",
      "date": "1916",
      "source_url": "https://commons.wikimedia.org/wiki/File:Einstein_Die_Grundlage_der_allgemeinen_Relativit%C3%A4tstheorie_Sonderdruck_1916_Titel.jpg",
      "direct_image_url": "https://upload.wikimedia.org/wikipedia/commons/9/97/Einstein_Die_Grundlage_der_allgemeinen_Relativit%C3%A4tstheorie_Sonderdruck_1916_Titel.jpg",
      "upstream_source_url": "https://www.kollerauktionen.ch/de/Buecher-Aufgeld-Einstein_-A.-Die-Grundlage-der-all-1214_544258.html?RecPos=95",
      "license": "Public domain; PD-Art (PD-old-auto-expired)",
      "license_rationale": "Commons marks this 1916 printed work public domain: Einstein died in 1955, so life-plus-70 copyright expired at the end of 2025; US copyright expired because it was published before 1931. The faithful two-dimensional reproduction is marked public domain.",
      "source_modifications": "Faithful photograph of printed title page from Koller Auktionen; no further source edits stated.",
      "alt": "Title page of Einstein’s 1916 separate edition of The Foundation of the General Theory of Relativity.",
      "file": "einstein-gr-1916.jpg",
      "license_url": "https://creativecommons.org/publicdomain/mark/1.0/",
      "verified_date": "2026-09-08",
      "modifications": "Proportionally resized to maximum dimension 1400 pixels; JPEG recompressed at quality 85 with macOS sips. No cropping or content alterations.",
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}