{
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    "id": "einstein.relativity_popular_en",
    "canonical_url": "https://prokopton42.com/en/works/einstein/relativity-popular-en/reference-section-0017/",
    "language": "en",
    "title": "Relativity: The Special and General Theory, English Translation",
    "author": "Albert Einstein",
    "date": "1916; English translation published in 1920",
    "summary": "This English translation carries Einstein’s introduction to special and general relativity. Through measurement, reference frames, and thought experiments, it leads readers from the limits of classical mechanics toward spacetime and geometric gravitation.",
    "learning": "Define a reference frame and operational simultaneity, understand relativistic invariants, and judge how far pedagogical analogies support the demonstration.",
    "long_summary": "Einstein begins with concrete measurement of positions and times to show that distant simultaneity requires a procedure. Relativistic transformations, mass-energy equivalence, and the equivalence principle progressively enlarge the framework.\n\nThe translation preserves an accessible chain of reasoning without removing every technical term. Its metaphors are controlled models, not self-sufficient proofs. Reading should maintain the connection among example, operational definition, and physical principle.",
    "historical_context": "The corpus manifests do not yet establish the precise place and circumstances of composition. The images below document the author’s world or the text’s transmission. They do not claim to show the exact scene of writing.",
    "material_world_label": "World of the world wars, 1914-1945",
    "material_world": {
        "technology": "Electricity, internal combustion, steel, aviation, radio, cinema, and mass production transform civilian life and warfare.",
        "science": "Relativity, quantum physics, chemistry, psychology, and genetics reshape knowledge within powerful institutions that are sometimes militarized.",
        "medicine": "X-rays, surgery, transfusion, antisepsis, and early antibiotics save more lives without universal access.",
        "transport": "Rail, cars, trams, ocean liners, and aircraft coexist. Armies mechanize mobility rapidly.",
        "agriculture": "Tractors, fertilizers, and breeding advance; rationing, blockade, and requisition expose fragile supplies.",
        "communication": "Telephone, telegraph, radio, newsreels, and newspapers reach mass audiences; propaganda and censorship use the same networks.",
        "clothing": "Suits, shorter dresses, coats, and hats coexist with uniforms and workwear. Shortages simplify cuts and materials."
    },
    "material_world_scenes": [
        {
            "asset": "/assets/timeline/landmarks/26-1939-ce/world-01.webp",
            "title": "Technology, science, and care",
            "description": "Electricity, internal combustion, steel, aviation, radio, cinema, and mass production transform civilian life and warfare. Relativity, quantum physics, chemistry, psychology, and genetics reshape knowledge within powerful institutions that are sometimes militarized. X-rays, surgery, transfusion, antisepsis, and early antibiotics save more lives without universal access."
        },
        {
            "asset": "/assets/timeline/landmarks/26-1939-ce/world-02.webp",
            "title": "Travel and communication",
            "description": "Rail, cars, trams, ocean liners, and aircraft coexist. Armies mechanize mobility rapidly. Telephone, telegraph, radio, newsreels, and newspapers reach mass audiences; propaganda and censorship use the same networks."
        },
        {
            "asset": "/assets/timeline/landmarks/26-1939-ce/world-03.webp",
            "title": "Farming and food",
            "description": "Tractors, fertilizers, and breeding advance; rationing, blockade, and requisition expose fragile supplies."
        },
        {
            "asset": "/assets/timeline/landmarks/26-1939-ce/world-04.webp",
            "title": "Clothing, women and men",
            "description": "Suits, shorter dresses, coats, and hats coexist with uniforms and workwear. Shortages simplify cuts and materials."
        }
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        "label": "Science and scientific thought"
    },
    "period": {
        "id": "contemporary",
        "label": "Contemporary era"
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        "fr"
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            "id": "care_of_soul",
            "label": "Care of the soul"
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        {
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            "label": "Empirical test"
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            "label": "Equivalence principle"
        },
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            "label": "Physical invariance"
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    "word_count": 30599,
    "word_counts_by_language": {
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        "fr": 29469
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        "leaf_en": "Section"
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    "representations": [
        {
            "language": "en",
            "text": "Of course we must refer the process of the propagation of light (and indeed every other process) to a rigid reference-body (co-ordinate system). As such a system let us again choose our embankment. We shall imagine the air above it to have been removed. If a ray of light be sent along the embankment, we see from the above that the tip of the ray will be transmitted with the velocity c relative to the embankment. Now let us suppose that our railway carriage is again travelling along the railway lines with the velocity v , and that its direction is the same as that of the ray of light, but its velocity of course much less. Let us inquire about the velocity of propagation of the ray of light relative to the carriage. It is obvious that we can here apply the consideration of the previous section, since the ray of light plays the part of the man walking along relatively to the carriage. The velocity W of the man relative to the embankment is here replaced by the velocity of light relative to the embankment. w is the required velocity of light with respect to the carriage, and we have The velocity of propagation ot a ray of light relative to the carriage thus comes out smaller than c . But this result comes into conflict with the principle of relativity set forth in Section V. For, like every other general law of nature, the law of the transmission of light in vacuo [in vacuum] must, according to the principle of relativity, be the same for the railway carriage as reference-body as when the rails are the body of reference. But, from our above consideration, this would appear to be impossible. If every ray of light is propagated relative to the embankment with the velocity c , then for this reason it would appear that another law of propagation of light must necessarily hold with respect to the carriage—a result contradictory to the principle of relativity.",
            "translator": "Robert W. Lawson",
            "source_id": "relativity_popular_en",
            "translation_type": "historical_translation"
        },
        {
            "language": "fr",
            "text": "Nous devons évidemment rapporter le processus de propagation de la lumière (et, en vérité, tout autre processus) à un corps de référence rigide (système de coordonnées). Choisissons de nouveau notre talus comme tel système. Nous imaginerons que l’air qui le surplombe a été retiré. Si un rayon lumineux est envoyé le long du talus, il résulte de ce qui précède que l’extrémité du rayon se propage avec la vitesse c par rapport au talus. Supposons maintenant que notre wagon se déplace de nouveau le long des rails avec la vitesse v, dans la même direction que le rayon lumineux, mais bien entendu à une vitesse très inférieure. Demandons-nous quelle est la vitesse de propagation du rayon lumineux par rapport au wagon. Il est évident que nous pouvons appliquer ici le raisonnement de la section précédente, puisque le rayon lumineux joue le rôle de l’homme marchant par rapport au wagon. La vitesse W de l’homme par rapport au talus est ici remplacée par la vitesse de la lumière par rapport au talus. w est la vitesse recherchée de la lumière par rapport au wagon, et nous avons\n\nLa vitesse de propagation d’un rayon lumineux par rapport au wagon se révèle donc inférieure à c. Mais ce résultat entre en conflit avec le principe de relativité exposé à la section V. Car, comme toute autre loi générale de la nature, la loi de propagation de la lumière dans le vide doit, selon le principe de relativité, être la même lorsque le wagon sert de corps de référence que lorsque les rails constituent le corps de référence. Or, d’après notre raisonnement précédent, cela semblerait impossible. Si chaque rayon lumineux se propage par rapport au talus avec la vitesse c, il semblerait en conséquence qu’une autre loi de propagation de la lumière doive nécessairement être valable par rapport au wagon, résultat qui contredit le principe de relativité.",
            "translator": "Codex gpt-5.6-sol",
            "edition": "Prokopton42 non-official AI translation, 2026-09-11",
            "source_id": "prokopton42-codex-translation:gpt-5.6-sol:corpus-passage-translation-v1",
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