This 1920 book originated as a newspaper article by Hendrik Lorentz, published in the Nieuwe Rotterdamsche Courant on November 19, 1919, shortly after the Royal Society confirmed light deflection during a solar eclipse. The publisher’s note claims that “not more than twelve persons in all the world are able to understand Einstein's Theory,” framing the text as a popular explanation. Lorentz, credited by Einstein with sharing the theory’s development, writes without equations, relying instead on a single recurring analogy: a falling box that mimics gravitational effects. The excerpts show a work that is less a systematic treatise than a journalistic bridge between technical relativity and a curious public.

The Falling-Box Analogy as Explanatory Engine

Lorentz’s central device is a thought experiment: imagine a person floating inside a box that is suddenly jerked upward. The person falls to the bottom, experiencing the same sensation as if gravity were present. This analogy, attributed to Einstein himself in a New York Times interview, recurs throughout the excerpts. Lorentz uses it to argue that “difform motion will in every case produce the same effects as gravitation.” The box appears in multiple contexts—first to introduce the equivalence principle, then to explain light deflection. By keeping the reader inside the box, Lorentz avoids abstract mathematics and instead builds intuition through a single, repeatable scenario. The analogy is not merely illustrative; it becomes the logical scaffold for predicting that light must bend in a gravitational field.

Mercury’s Orbit as a Concrete Test

Lorentz presents the anomalous precession of Mercury’s perihelion as a decisive victory for Einstein’s theory. He notes that after accounting for planetary disturbances, “there remained an inexplicable phenomenon—an extremely slow turning of the ellipsis described by Mercury on its own plane.” Leverrier had calculated this residual shift as forty-three seconds per century. Einstein’s formulas, Lorentz reports, predicted exactly that value. The passage is notable for its restraint: Lorentz does not exaggerate the drama but states the result plainly. This section grounds the theory in a specific, measurable astronomical problem, contrasting with the more abstract falling-box discussion. It also reveals the book’s structure: moving from a conceptual analogy to a historical puzzle that the theory resolves.

Light Deflection and the 1919 Eclipse

The excerpts culminate in the eclipse observations that revived interest in relativity. Lorentz explains that a ray of light grazing the sun should be bent by 1.75 seconds of arc, “approximately the thousandth part of the apparent diameter of the sun.” He derives this prediction from the falling-box analogy: if a projectile and a light pulse travel side by side in a falling compartment, both must curve when observed from a gravitational field. The language is careful—Lorentz calls the bending “much too light on the surface of the earth to be observed” but significant near the sun. The text does not describe the actual 1919 expedition results; instead, it prepares the reader to understand why such an observation would confirm the theory. This section shows Lorentz’s method: building from a simple mental model to a quantitative, testable claim.

Readers should note that this text is not a comprehensive derivation but a snapshot of relativity in the months after its first major experimental confirmation. Lorentz writes as a physicist addressing a newspaper audience, so the arguments are compressed and the analogies repeated. The book’s value lies in seeing how a leading figure of classical physics translated Einstein’s radical ideas into accessible terms—without equations, but with a clear logical thread from falling boxes to planetary orbits.