---
slug: the-falling-cat
passed: 2026-10-18
by: the assay line (research/assay-line/claude-1018/), Claude fixer (claude-opus-5-5) directed by claude-assaying-boyle-1014; source record by a Claude agent (claude-sonnet-5-5), checked by a Claude agent (claude-opus-5-5)
checked: 107
confirmed: 78
wrong: 21
unverifiable: 3
observed: 5
stale: 0
---

This was a directed repair pass over the 19 triage items in research/assay-line/claude-1018/the-falling-cat/triage.json, read at 0b1d854e27, with the evidence for each WRONG item re-read before editing (Lecornu, CR 119 p. 899 and Guyou, CR 119 pp. 717-718 from the archive.org djvu text; Montgomery 1993 p. 193 by OCR of the scan; the Europe PMC record of Jusufi et al. 2010) and the MINOR items checked against those same texts, the page's own table and verify.mjs output. It carries forward the checker's claim lines from research/assay-line/claude-1018/the-falling-cat/N2-claude.md, including its CONFIRMED, OBSERVED and three UNVERIFIABLE lines, without claiming a fresh audit of them. The 21 lines counted under wrong are six WRONG lines (three false statements: the Lecornu credit, in the body and in the dek, the 1993 dating of the gauge-theory recognition, and the 2010 tailed vs tailless study with its citation), each corrected with a dated line on the page and in the markdown, and 15 MINOR near-misses, all fixed without a page line. A repair pass changed two carried-forward CONFIRMED lines (dek-guyou-lecornu to WRONG, rel-tailless to MINOR) after the fix-check found them to be missed copies of corrected sentences.

## Claims
- CONFIRMED | Drop a cat belly-up with no spin and it lands feet-down, having turned a half-circle while its angular momentum stayed exactly zero, start to finish, with nothing to push on. | https://pentagono.uniandes.edu.co/~jarteaga/geosem/taller7/minicursoJK-Uniandes/robotic%20examples/kane.pdf | [dek-cat-lands] p. 663: "IT is well known that falling cats usually land on their feet and, moreover, that they can manage to do so even if released from complete rest while upside-down." Zero angular momentum: p. 667 "must be equal to zero at all times (because it is initially equal to zero by hypothesis)".
- CONFIRMED | A rigid body simply cannot do this. | https://archive.org/download/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18_djvu.txt | [dek-rigid] Levy, CR 119 p. 719: "Ce serait manifestement impossible s’il était assujetti à tourner comme un système invariable."
- MINOR | Kane & Scher proved the half-turn in 1969 on a NASA grant | https://pentagono.uniandes.edu.co/~jarteaga/geosem/taller7/minicursoJK-Uniandes/robotic%20examples/kane.pdf | [dek-ks-nasa] NASA grant confirmed (footnote, read from the page image: "This investigation was supported, in part, by NASA Research Grant NGR-05-020-209."). "proved the half-turn" is stronger than the paper: the half-turn is imposed, not derived ("if ψ(2π) is set equal to π, this solution yields the relationship" (8), p. 666), the closed form exists only for alpha = 0, which the paper calls "an unsatisfactory value", eq. (8) "is, essentially, a result obtained by Rademaker and Ter Braak", and the paper concludes it "explains" the phenomenon. FIXED: the markdown dek now says Kane & Scher showed in 1969, on a NASA grant, how one cycle can overturn the cat (Kane & Scher p. 666 re-read via the triage note: psi(2pi) = pi is imposed and the bend solved for); MINOR, no page correction line.
- CONFIRMED | Kane & Scher proved the half-turn in 1969 on a NASA grant | https://ntrs.nasa.gov/api/citations/19690058843 | [dek-ks-grant-ntrs] NTRS 19690058843, "A dynamical explanation of the falling cat phenomenon.", fundingNumbers NGR-05-020-209 (CONTRACT_GRANT). Covers the NASA-grant half of the sentence.
- WRONG | Guyou and Lecornu had the right picture within weeks of Marey's 1894 photographs, not seventy-five years later | https://archive.org/download/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18_djvu.txt | [dek-guyou-lecornu] Guyou's note is in the 29 Oct 1894 session (p. 717), the same issue as Marey's note; Lecornu's is in the 26 Nov 1894 session (p. 899, https://archive.org/download/comptes-rendus-hebdomadaires-academie-des-sciences_1894-11-26_119_22/comptes-rendus-hebdomadaires-academie-des-sciences_1894-11-26_119_22_djvu.txt). Both well under 75 years; "within weeks" holds. What Lecornu's picture was is a separate line (body-lecornu-picture). Repair pass: the dek's 'Guyou and Lecornu had the right picture' hands Lecornu the picture body-lecornu-picture corrects (Lecornu, CR 119 p. 899: "sans modifier, à aucun instant, la forme extérieure non plus que les moments d'inertie"). FIXED: dek now 'Guyou had the right picture within weeks of Marey's 1894 photographs, and Lecornu another route, not seventy-five years later'; covered by the Lecornu Corrected 2026-10-18 line.
- CONFIRMED | and no, it isn't the tail (tailless cats right themselves fine) | https://en.wikipedia.org/wiki/Cat_righting_reflex | [dek-tail] lead: "The tail seems to help but cats without a tail also have this ability".
- CONFIRMED | the turn is the holonomy of a closed loop in shape space: a geometric phase | https://people.ucsc.edu/~rmont/papers/cat.PDF | [dek-holonomy] Montgomery 1993 p. 194: "Kane and Scher calculated the reorientation, or holonomy, suffered when their model cat traversed a particular class of loops in its shape space." WP Falling cat problem says the same in terms of a connection.
- CONFIRMED | Swing a 27.9° waist-bend around once and the net turn is 179.99°, a complete flip | research/the-falling-cat/verify.mjs | [dek-flip-2799] verify.mjs at ca0306b7ff, and the published copy https://artwaste.land/checks/research/the-falling-cat/verify.mjs (byte-identical) run in an empty directory: exit 0, 10 passed, 0 failed: "best single circle: bend 27.92 deg -> net rotation 179.994 deg". 27.92 rounds to the page's 27.9.
- CONFIRMED | do it twice and you're back where you started | research/the-falling-cat/verify.mjs | [dek-twice] verify.mjs at ca0306b7ff, and the published copy https://artwaste.land/checks/research/the-falling-cat/verify.mjs (byte-identical) run in an empty directory: exit 0, 10 passed, 0 failed: "two circles at that bend: net rotation 0.00 deg".
- CONFIRMED | A one-motion wiggle, by contrast, turns nothing at all | research/the-falling-cat/verify.mjs | [dek-wiggle] verify.mjs at ca0306b7ff, and the published copy https://artwaste.land/checks/research/the-falling-cat/verify.mjs (byte-identical) run in an empty directory: exit 0, 10 passed, 0 failed: wiggle net 2.11e-5 deg.
- CONFIRMED | The immersive page is a live two-segment cat whose overall rotation is solved each instant to hold angular momentum at zero, and it does, to fifteen digits, while the body flips. | public/strata/the-falling-cat/index.html | [dek-live-l] physStep() in the page script is the same model as verify.mjs (solves Om = -inv3(Il) b, returns Lres); verify.mjs prints max/L/ = 7.46e-15 for the flip. The readout is the residual of that solve.
- MINOR | Every number is recomputed offline in `research/the-falling-cat/verify.mjs` two independent ways (a from-scratch multibody simulator and Kane & Scher's published 1969 equation), which agree that one circle of the waist is one flip of the cat. | research/the-falling-cat/verify.mjs | [dek-verify-two-ways] "Every number is recomputed offline ... two independent ways": verify.mjs computes each figure once. The simulator (checks A-C) runs at J/I = 0.0583, the Kane-Scher equations (check D) at J/I = 0.25, and no figure is computed by both. The agreement itself holds when tested: run at J/I = 0.25 the same simulator flips at a 59.43 deg bend, the Eq. 8 value (see body-two-pieces), but the shipped file does not do that. FIXED: the markdown body now says every number is recomputed by one of two independent formalisms, and each finds one circle of the waist is one flip; the verify.mjs header no longer says the two are checked against each other; MINOR, no page correction line.
- CONFIRMED | was exactly zero the whole way down, and nothing pushed on it | https://archive.org/download/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18_djvu.txt | [body-l-zero] Marey p. 716: "dans les premiers instants de sa chute, l'animal n’avait encore aucune tendance à tourner ni d’un côté, ni de l’autre". "Exactly zero" is the idealised statement; Kane & Scher p. 667 take it as the hypothesis.
- CONFIRMED | Whatever angular momentum you start with, you keep. Drop the cat with none, and it has none until it lands. | https://pentagono.uniandes.edu.co/~jarteaga/geosem/taller7/minicursoJK-Uniandes/robotic%20examples/kane.pdf | [body-ang-mom-kept] p. 667: "the angular momentum of the system relative to the mass center of the system must be equal to zero at all times (because it is initially equal to zero by hypothesis)".
- CONFIRMED | Zero angular momentum and rigid means zero angular velocity | https://archive.org/download/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18_djvu.txt | [body-rigid-zero] Levy p. 719, as dek-rigid.
- MINOR | and for a century people insisted it was: that the animal must shove off the handler's hand on the way out | https://en.wikipedia.org/wiki/Falling_cat_problem | [body-century-handshove] Wikipedia: "many physicists at the time maintained that the cat was still \"cheating\"" (after the 1894 photographs, not for a century before). Marey p. 714 says only "Quelques personnes ont pu croire que l’animal ... prend appui sur les mains". Deprez (CR 119 p. 768) says the textbook error was Delaunay's and "tous les auteurs de Traités de Mécanique rationnelle". No source gives "for a century" or "insisted". FIXED: 'for a century people insisted it was' is now 'some people believed it was' (Marey p. 714, re-read: 'Quelques personnes ont pu croire'); MINOR, no page correction line.
- MINOR | and for a century people insisted it was: that the animal must shove off the handler's hand on the way out | https://archive.org/download/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18_djvu.txt | [body-century-marey] Same claim. Marey p. 714: "Quelques personnes ont pu croire" (some people may have believed): weaker than "for a century people insisted". FIXED with body-century-handshove (same sentence); MINOR, no page correction line.
- CONFIRMED | In 1894 Étienne-Jules Marey settled it with a camera | https://archive.org/download/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18_djvu.txt | [body-marey-settled] Marey p. 716: "L'inspection de ces figures exclut tout d’abord l’idée que l’animal s'imprime un mouvement rotatif, en prenant un point d’appui sur les mains de l'opérateur". Deprez (https://archive.org/download/comptes-rendus-hebdomadaires-academie-des-sciences_1894-11-05_119_19/comptes-rendus-hebdomadaires-academie-des-sciences_1894-11-05_119_19_djvu.txt, p. 768) confirms the experiment was communicated to the Academy.
- CONFIRMED | his falling cat begins each drop with no rotation whatsoever, and turns over anyway | https://archive.org/download/sim_nature-uk_1894-11-22_51_1308/sim_nature-uk_1894-11-22_51_1308_djvu.txt | [body-marey-norot] Nature 51 p. 81 (archive OCR, and the PDF https://www.nature.com/articles/051080a0.pdf): "The first few images in each of the two series show that at the beginning of the fall the cat exhibits no tendency to turn either one side or the other."
- CONFIRMED | the same mathematics behind a Foucault pendulum's slow drift and the twist of polarized light through a coiled fiber | https://en.wikipedia.org/wiki/Geometric_phase | [body-geom-phase-analogues] "The Foucault pendulum is an example from classical mechanics that is sometimes used to illustrate the geometric phase." and section "Polarized light in an optical fiber".
- CONFIRMED | The net turn is the holonomy of a loop | https://people.ucsc.edu/~rmont/papers/cat.PDF | [body-holonomy-connection] Montgomery 1993 p. 194, "reorientation, or holonomy"; p. 193 "The gauge field summarizes the condition that the angular momentum be zero."
- CONFIRMED | It depends only on the path, not on how fast the cat runs it | research/the-falling-cat/verify.mjs | [body-speed-indep] verify.mjs at ca0306b7ff, and the published copy https://artwaste.land/checks/research/the-falling-cat/verify.mjs (byte-identical) run in an empty directory: exit 0, 10 passed, 0 failed: check B "121.6575 deg vs 121.6575 deg".
- MINOR | swinging a 27.9° waist bend once around delivers a net body rotation of 179.99° - a complete flip, belly-up to feet-down, to within four thousandths of a degree | research/the-falling-cat/verify.mjs | [body-2799-flip] The bend and 179.99 deg are right, but "to within four thousandths of a degree" does not match the page's own table or the verifier: 180 - 179.994 = 0.006 deg (six thousandths). The memory log repeats "within 4 thousandths". FIXED: 'four thousandths' is now 'six thousandths' (verify.mjs prints flipAngleDeg 179.994, so 180 - 179.994 = 0.006); MINOR, no page correction line.
- CONFIRMED | Run the circle twice and the turns add to a full revolution: the cat is back exactly belly-up. | research/the-falling-cat/verify.mjs | [body-twice] verify.mjs at ca0306b7ff, and the published copy https://artwaste.land/checks/research/the-falling-cat/verify.mjs (byte-identical) run in an empty directory: exit 0, 10 passed, 0 failed: two circles 0.00 deg.
- CONFIRMED | recomputed at a thousand integration steps and at thirty thousand, it agrees to five figures | research/the-falling-cat/verify.mjs | [body-mesh] verify.mjs at ca0306b7ff, and the published copy https://artwaste.land/checks/research/the-falling-cat/verify.mjs (byte-identical) run in an empty directory: exit 0, 10 passed, 0 failed: 1k/3k/10k/30k steps give 121.65752 121.65751 121.65751 121.65751.
- CONFIRMED | working on a NASA grant to learn how weightless astronauts could turn around | https://ntrs.nasa.gov/api/citations/search?q=%22NGR-05-020-209%22 | [body-ks-grant-astronauts] Fifteen NTRS records on NGR-05-020-209, e.g. 19700043129 "Human self-rotation by means of limb movements", abstract "Weightless astronaut self rotation by limb maneuvers producing pitch and yaw motion"; 19720053360 "Experimental investigation of an astronaut maneuvering scheme." The 1969 cat paper itself does not mention astronauts.
- MINOR | modeled the cat as two such halves and proved it exactly | https://pentagono.uniandes.edu.co/~jarteaga/geosem/taller7/minicursoJK-Uniandes/robotic%20examples/kane.pdf | [body-ks-two-halves-proved] Two identical bodies: confirmed ("the two bodies are identical", p. 665). "proved it exactly", following "That a single circling of the waist produces precisely a half-turn is not a coincidence of this toy", reverses the logic: the half-turn is the condition the bend is chosen to meet ("If ψ(2π) is not equal to ±π, increase β and integrate again", p. 666); exact closed form only at alpha = 0, which they reject; that result "is, essentially, a result obtained by Rademaker and Ter Braak". The paper says "this theory explains the phenomenon". FIXED: 'proved it exactly: drive the maneuver through one full cycle and the body overturns' is now 'showed that, with the right bend, one full cycle of the maneuver makes the body overturn', and the lead-in 'produces precisely a half-turn is not a coincidence' is now 'can produce a half-turn is not a quirk'; MINOR, no page correction line.
- CONFIRMED | drive the maneuver through one full cycle and the body overturns - turns through π, a half-circle - with angular momentum identically zero | https://pentagono.uniandes.edu.co/~jarteaga/geosem/taller7/minicursoJK-Uniandes/robotic%20examples/kane.pdf | [body-ks-overturn] p. 665 (page image): "overturning has occurred when ψ = ±π if A and B each have the same orientation in Q at these two instants"; motions with theta from 0 to 2 pi and psi = +-pi at the end, at zero angular momentum (p. 667). True as a description of the motions they study.
- CONFIRMED | Feeding their own published equation the inertia they measured from a real cat reproduces the classic result that the maneuver needs a bend of roughly 60° | https://pentagono.uniandes.edu.co/~jarteaga/geosem/taller7/minicursoJK-Uniandes/robotic%20examples/kane.pdf | [body-ks-60] p. 666 (page image): "with J/I = 0·25, which is a realistic value,* equation (8) leads to a value of nearly 60° for β"; footnote: measured "with the assistance of Dr. James Robinson of the NASA Ames Research Center, on fourteen segments of a dead cat." The paper offers the 60 deg as the reason alpha = 0 is "an unsatisfactory value", which the page does not say, but the figure and its derivation are as stated.
- OBSERVED | Two unrelated pieces of mathematics, a half-century and a different formalism apart, agree on the same sentence: one circle of the waist is one flip of the cat. | recreated: node probe2.mjs in /home/liam/.assay-line/claude-1018/the-falling-cat/N2/probe (the CAT simulator of verify.mjs at ca0306b7ff with rho = 0.4364, so J/I = 0.25) | [body-two-pieces] The simulator flips at bend 59.43 deg (net 179.989 deg; 58 deg gives 175.343, 60 deg 178.154), the same 59.43 deg Eq. 8 gives. So the two formalisms do agree when given the same inertia. verify.mjs itself never makes this comparison (it runs them at J/I 0.0583 and 0.25); see check-two-ways.
- CONFIRMED | the check measures turn-per-area converging to a fixed curvature as the loop shrinks | research/the-falling-cat/verify.mjs | [body-area-law] verify.mjs at ca0306b7ff, and the published copy https://artwaste.land/checks/research/the-falling-cat/verify.mjs (byte-identical) run in an empty directory: exit 0, 10 passed, 0 failed: net/area 0.6462, 0.7227, 0.7653 for areas 4e-2, 1e-2, 2.5e-3 (steps shrinking).
- CONFIRMED | It is the same shape of statement as Gauss–Bonnet, or the way a vector parallel-transported around a triangle on a globe comes home rotated by the enclosed area. | https://en.wikipedia.org/wiki/Geometric_phase | [body-gaussbonnet] "Consider a vector around a closed loop, e.g. a spherical triangle, on the sphere: The angle by which it twists, α, is proportional to the area inside the loop"; "by the Gauss–Bonnet theorem, the phase shift is given by the enclosed solid angle."
- MINOR | On 29 October 1894 Marey presented a strip of chronophotographs | https://archive.org/download/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18_djvu.txt | [body-marey-1029] Marey's Note is printed in the 29 Oct 1894 session (p. 714), but Levy's note in that same issue (p. 718) opens "Les expériences de M. Marey ont soulevé, à la dernière séance, cette question", i.e. at the previous session, 22 Oct; Appell (5 Nov, p. 770) uses "à la dernière séance" the same way for 29 Oct. Gbur, the page's own source, dates the meeting "October 22, 1894" (https://skullsinthestars.com/2020/01/07/falling-felines-at-bbc-science-focus/). The 22 Oct printed issue has no Marey note (searched; positive control: the same search finds Marey in the 29 Oct issue). The photographs were apparently shown 22 Oct and the Note printed 29 Oct. FIXED: 'On 29 October 1894' is now 'In October 1894' (Levy, CR 119 p. 718, re-read: 'à la dernière séance'); MINOR, no page correction line.
- MINOR | a falling cat caught a dozen times in a single plunge | https://www.nature.com/articles/051080a0.pdf | [body-dozen] Nature's reproduction (page image, p. 80) of Fig. 1, one plunge, has 10 exposures in the upper strip and 9 in the lower ("the lower is a continuation of the upper"), about 19; Fig. 2 likewise 10 and 9. N1 counted about 11 and 9 on the CR page. "A dozen times in a single plunge" undercounts; no source states twelve. FIXED: 'a dozen times' is now 'some twenty times' (Nature's reproduction, 10 + 9 exposures per plunge, per the note); MINOR, no page correction line.
- CONFIRMED | Nature reported that the images "have excited considerable interest," | https://www.nature.com/articles/051080a0.pdf | [body-nature-interest] p. 80, read from the page image: "M. MAREY'S recent photographs of a falling cat ... have excited considerable interest." Quote exact.
- CONFIRMED | and noted, with period dryness, that the cat's "expression of offended dignity… at the end of the first series indicates a want of interest in scientific investigation." | https://www.nature.com/articles/051080a0.pdf | [body-nature-dignity] p. 80, read from the page image: "The expression of offended dignity shown by the cat at the end of the first series indicates a want of interest in scientific investigation." The page's ellipsis stands for "shown by the cat"; the rest is exact.
- CONFIRMED | and noted, with period dryness, that the cat's "expression of offended dignity… at the end of the first series indicates a want of interest in scientific investigation." | https://en.wikipedia.org/wiki/Falling_cat_problem | [body-nature-dignity-wp] secondary; same sentence quoted contiguously.
- CONFIRMED | The pictures were taken precisely to test the hand-shove hypothesis, and they refuted it: at release the cat is not rotating, so it cannot have pushed off anything. | https://archive.org/download/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18_djvu.txt | [body-handshove-test] Marey p. 715: "Comme l'œil est incapable de saisir ce qui se passe réellement dans ces cas, j'ai recouru à la chronophotographie"; p. 716 the figures exclude the hand fulcrum and the first images show no tendency to turn. "precisely to test the hand-shove hypothesis" is a little strong (he also tested the air hypothesis) but fair.
- UNVERIFIABLE | It is often said the cat then "stumped physics for seventy-five years," until Kane and Scher in 1969. | WebSearch for "stumped" + "seventy-five years"/"75 years" + falling cat + Kane Scher; Google Books API (quota exhausted, 429); Bing curl fallback (its parser returned nothing even for "falling cat problem", so not used) | [body-stumped] The exact quoted phrase was not found. The gist is common: Wikipedia "The problem was initially solved in 1969"; a University of Toronto colloquium abstract (in search results) "has stumped physicists since the 19th century". Positive control: the same search returned the Wikipedia page and the Kane & Scher PDF.
- MINOR | the engineer Émile Guyou | https://fr.wikipedia.org/wiki/%C3%89mile_Guyou | [body-guyou-engineer] fr.wikipedia: "officier de marine et scientifique français"; capitaine de frégate, professor at the École navale, elected to the Académie "dans la section de géographie et de navigation" in January 1894. Levy calls him "le commandant Guyou" (CR 119 p. 718). Not an engineer. FIXED: 'the engineer Émile Guyou' is now 'the naval officer Émile Guyou' (Levy, CR 119 p. 718, re-read: 'le commandant Guyou'); MINOR, no page correction line.
- CONFIRMED | the mechanician Léon Lecornu | https://en.wikipedia.org/wiki/L%C3%A9on_Lecornu | [body-lecornu-mechanician] "a French engineer and physicist"; "elected a member of l'Académie des sciences in 1910 (section de mécanique)". His 1894 note is filed under MÉCANIQUE.
- CONFIRMED | laid out the right picture: the cat bends and lets its front and rear halves rotate in opposite senses, varying how much each resists turning by tucking or extending its legs, so the two contributions to angular momentum cancel and the net stays zero while the body comes around | https://archive.org/download/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18_djvu.txt | [body-guyou-picture] Guyou pp. 717-718: "il donne toujours, par l'extension de ses membres, un grand moment d'inertie à la partie qui tourne dans le sens négatif"; inertias "I quand les membres sont allongés" and i (OCR "#") "quand ils sont ramenés le long du corps"; the sum of areas "reste constamment nulle".
- WRONG | laid out the right picture: the cat bends and lets its front and rear halves rotate in opposite senses, varying how much each resists turning by tucking or extending its legs, so the two contributions to angular momentum cancel and the net stays zero while the body comes around | https://archive.org/download/comptes-rendus-hebdomadaires-academie-des-sciences_1894-11-26_119_22/comptes-rendus-hebdomadaires-academie-des-sciences_1894-11-26_119_22_djvu.txt | [body-lecornu-picture] Lecornu, CR 119 p. 899, shows the opposite of the mechanism the page gives him: the turn "peut être obtenu sans modifier, à aucun instant, la forme extérieure non plus que les moments d'inertie" (OCR "ob- tenu"), e.g. "un ophidien dont l’axe serait assujetti à conserver une figure invariable". His model is a body whose cross-sections each rotate one way while the whole turns the other; nothing tucks or extends, and no front and rear halves. FIXED: re-read Lecornu, CR 119 p. 899 (26 Nov 1894 djvu.txt) and Guyou pp. 717-718 (29 Oct djvu.txt) on 2026-10-19. The tuck-and-extend picture is now credited to Guyou alone, and Lecornu is said to have shown a body could in principle turn itself over without changing its outer shape or moments of inertia; Corrected 2026-10-18 line added on the page and in the markdown.
- CONFIRMED | in a matter of weeks | https://archive.org/download/comptes-rendus-hebdomadaires-academie-des-sciences_1894-11-26_119_22/comptes-rendus-hebdomadaires-academie-des-sciences_1894-11-26_119_22_djvu.txt | [body-lecornu-weeks] Session of Monday 26 Nov 1894, p. 899, four weeks after 29 Oct (five after 22 Oct); Guyou the same day as Marey's Note.
- MINOR | What 1969 added was not the idea but its rigor - a complete dynamical model | https://pentagono.uniandes.edu.co/~jarteaga/geosem/taller7/minicursoJK-Uniandes/robotic%20examples/kane.pdf | [body-1969-rigor] Kane & Scher p. 663: "Rademaker and Ter Braak [4] proposed a model capable of performing motions compatible with (I) and (II)"; p. 666 eq. (8) "is, essentially, a result obtained by Rademaker and Ter Braak". Montgomery (https://people.ucsc.edu/~rmont/papers/cat.PDF, p. 193): "Kane and Scher, and earlier Rademaker and ter Braak, proposed a specific strategy". A dynamical model with this result predates 1969; 1969 added one meeting requirement (III). FIXED: the sentence now reads 'What 1969 added, after an earlier model by Rademaker and ter Braak, was not the idea but its rigor' (Kane & Scher p. 663, Montgomery p. 193 re-read: 'Kane and Scher, and earlier Rademaker and ter Braak, proposed a specific strategy'); MINOR, no page correction line.
- WRONG | what 1993 added, in Richard Montgomery's "gauge theory of the falling cat," was the recognition that this is the same geometric-phase machinery that runs through gauge field theory and Berry's phase | https://people.ucsc.edu/~rmont/papers/cat.PDF | [body-montgomery] Montgomery's own introduction (p. 193, OCR of the scan) places the recognition before 1993: "In earlier papers [22], [21] we developed a general theory for the attitude, or orientation control, of deformable bodies in freefall with zero angular momentum. These papers were outgrowths of work by Wilczek and Shapere [27] and Guichardet [12]. The main point of these earlier works is that a dictionary can be developed between the gauge theory ... and the problems occuring in the orientation control of deformable bodies." and "The purpose of the present paper is to apply our general theory to the Kane-Scher cat." Shapere & Wilczek 1989 (cited on the page) abstract: "a gauge structure over the space of shapes ... the net change in orientation of a body with angular momentum zero". Berry's phase is not named in pp. 193-195. FIXED: re-read Montgomery 1993 p. 193 (OCR of people.ucsc.edu/~rmont/papers/cat.PDF) on 2026-10-19. The page now says the gauge-theory recognition came before 1993, in work by Shapere and Wilczek (1989), Guichardet and Montgomery himself, whose 1993 paper applied it to the Kane-Scher cat; the unsourced 'and Berry's phase' went with the old sentence; Corrected 2026-10-18 line added on the page and in the markdown.
- UNVERIFIABLE | the dramatic tale of the Academy erupting in "scandal," accusing the cat of fraud, is later journalism - no primary record of an uproar survives | Full OCR text of Comptes Rendus 119 for 22 Oct, 29 Oct, 5 Nov, 12 Nov and 26 Nov 1894 searched for scandal, fraud, trich, superch, impost, tumult, emotion: no hit on the cat (fraud: 1 hit about alcohol; trich: Tricholoma). Positive control: the same files give 7, 3 and 2 hits for "chat" and find Guyou, Levy, Deprez, Lecornu. WebSearch for a scandal/uproar account | [body-scandal] No primary record of a scandal found; newspapers not searched. But the record shows debate, and the page's own source tells it more strongly: Lecornu (26 Nov) "la question, récemment débattue devant elle"; Gbur (https://skullsinthestars.com/2020/01/07/falling-felines-at-bbc-science-focus/): "The revelations of the photographs threw the meeting into disarray" and a member said Marey "had presented them with a scientific paradox in direct contradiction with the most elementary mechanical principles." The negative cannot be confirmed.
- CONFIRMED | The hand-shove idea was a sober hypothesis Marey set out to test, not an accusation hurled across a hall. | https://archive.org/download/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18_djvu.txt | [body-handshove-hypothesis] Marey p. 714 "Quelques personnes ont pu croire ..."; Deprez p. 768 (https://archive.org/download/comptes-rendus-hebdomadaires-academie-des-sciences_1894-11-05_119_19/comptes-rendus-hebdomadaires-academie-des-sciences_1894-11-05_119_19_djvu.txt) asked Marey to submit the question "au contrôle de la photographie instantanée" (OCR "pho- tographie").
- MINOR | Tailless and bobtailed cats - Manx cats - right themselves just as well | https://en.wikipedia.org/wiki/Cat_righting_reflex | [myth-manx] The source supports "cats without a tail also have this ability" but not "just as well": the same sentence says "The tail seems to help". The page's support for "just as well" is the 2010 study, which is WRONG (myth-2010-study). FIXED: 'right themselves just as well' is now 'right themselves too'; MINOR, no page correction line.
- WRONG | a 2010 study comparing tailed and tailless air-righting found no difference | https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=EXT_ID:21098954&resultType=core&format=json | [myth-2010-study] Jusufi, Kawano, Libby & Full 2010, Bioinspir. Biomim. 5(4) 045001, the study the page cites for this: the abstract opens "Unlike the falling cat, lizards can right themselves in mid-air by a swing of their large tails" and reports a gecko model and robot in which tails produce the rotation ("Our model predicted an increase in body roll and turning as tails increase in length"). It is not a tailed vs tailless comparison and reports no "no difference". Full text not readable (iopscience bot challenge; the Wayback copy of the PDF URL is the abstract page). FIXED: re-read the Europe PMC record (PMID 21098954) on 2026-10-19: a gecko-tail model and robot paper. The sentence is removed (no other source for it found; Fredrickson 1989, Phys. Teach. 27, 620, located on Crossref as 10.1119/1.2342893 but not read, so not cited); Corrected 2026-10-18 line added on the page and in the markdown.
- WRONG | a 2010 study comparing tailed and tailless air-righting found no difference | https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=EXT_ID:21098954&resultType=core&format=json | [myth-2010-study-none] Same claim; N1 and I found no other 2010 study. N1 searched Crossref, OpenAlex and WebSearch; the nearest real source is J. E. Fredrickson 1989, "The tail-less cat in free fall", Phys. Teach. 27 620-5 (Essen & Nordmark ref. [5]), which is not 2010 and was not read. FIXED with myth-2010-study (same sentence, removed); covered by the same Corrected 2026-10-18 line.
- UNVERIFIABLE | The tail's moment of inertia is far too small to supply the turn. | Wikipedia Cat righting reflex and Falling cat problem; Essen & Nordmark 2018 full text (no tail inertia figure); Jusufi 2010 and 2011 abstracts | [myth-tail-inertia] No measured cat-tail moment of inertia found. Wikipedia says only "The tail seems to help".
- CONFIRMED | A real cat may use it for a touch of fine adjustment, but the flip does not come from the tail - it comes from the spine and legs. | https://en.wikipedia.org/wiki/Cat_righting_reflex | [myth-tail-fine] "The tail seems to help but cats without a tail also have this ability, since a cat mostly turns by moving its legs and twisting its spine in a certain sequence."
- CONFIRMED | This was Marey's whole point in 1894: air resistance plays no role in the righting. | https://archive.org/download/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18_djvu.txt | [myth-air] Marey p. 716: "Quant à l'hypothèse d’un appui sur la résistance de l'air, elle n’est pas plus admissible". "Marey's whole point" is rhetoric (his conclusion is the inertia mechanism) but the fact is his.
- CONFIRMED | The cat would turn over just the same in a vacuum. | https://archive.org/download/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18_djvu.txt | [myth-vacuum] Levy p. 718 poses whether the cat can turn "alors même qu'il serait dans le vide" and reports Guyou "a opiné pour l’affirmative"; the mechanism needs no air.
- CONFIRMED | For something tiny - a falling insect - air torques can matter; for a cat they don't. | https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=EXT_ID:21930662&resultType=core&format=json | [myth-insect] Jusufi et al. 2011 abstract: "experiments with stick insects ... suggest that aerodynamic torques acting on the limbs and body may play a dominant role in the righting process for small invertebrates."
- CONFIRMED | Net angular momentum is zero at the start and stays zero to the landing. | https://archive.org/download/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18_djvu.txt | [myth-angmom-zero] Guyou pp. 717-718: "cette somme reste constamment nulle".
- CONFIRMED | Conservation is the rule the trick respects, not the rule it breaks. | https://en.wikipedia.org/wiki/Falling_cat_problem | [myth-conservation] "The apparent contradiction with the law of conservation of angular momentum is resolved because the cat is not a rigid body".
- CONFIRMED | down to a 2026 study of the unusually twistable feline thoracic spine | https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=EXT_ID:41734949&resultType=core&format=json | [foot-spine-2026] Higurashi et al., Anat Rec, first published 2026-02-24: "The thoracic region exhibited a larger range of motion, a larger neutral zone, and lower stiffness than the lumbar region, indicating greater torsional flexibility."
- CONFIRMED | sequence the rotation front-to-back | https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=EXT_ID:41734949&resultType=core&format=json | [foot-frontback] "During air-righting, anterior trunk rotation was completed earlier than posterior trunk rotation."
- MINOR | the scholarly consensus is a combination, not one neat model | https://iopscience.iop.org/article/10.1088/1361-6404/aaac06/pdf (read from http://web.archive.org/web/20180722031421id_/http://iopscience.iop.org/article/10.1088/1361-6404/aaac06/pdf) | [foot-consensus] Essen & Nordmark do back a blend, hedged: Conclusions, "Real cats of course have many more degrees-of-freedom and probably optimise a combination of the ‘legs in-legs out’ and ‘tuck and turn’ methods." (the source's dash in legs in-legs out rendered as a hyphen) But they describe no consensus: section 1, "This is not uncontroversial, however. There are in fact two schools of thought", and the tuck-and-turn school "seems to be the most popular nowadays". "Consensus" overstates "probably". (N1 wrote that they "do not say real cats blend the two"; they do.) Gbur 2019 not read. FIXED: 'the scholarly consensus is a combination' is now 'the best current view is a combination', and the sources line 'Consensus that real cats blend mechanisms' is now 'That real cats probably blend mechanisms'; MINOR, no page correction line.
- OBSERVED | the folklore numbers you'll see - a cat "needs 30 cm" or "rights in 0.3 seconds" - are repeated everywhere but trace to no measurement we could find | memory/log.d/2026-06-29T2340Z-the-falling-cat.md | [foot-lore-numbers] The log records the search: "the 'needs 30 cm / rights in 0.3 s' numbers (repeated everywhere, traced to no measurement)", done by five research subagents. The raw search is not kept.
- CONFIRMED | Real cats are richer than two rigid rods | https://iopscience.iop.org/article/10.1088/1361-6404/aaac06/pdf (read from http://web.archive.org/web/20180722031421id_/http://iopscience.iop.org/article/10.1088/1361-6404/aaac06/pdf) | [foot-real-cats] section 1: "The most conspicuous feature of these is a considerable twist of the front relative to the hind of the cat."
- CONFIRMED | Nature reported that the images "have excited considerable interest," | https://archive.org/download/sim_nature-uk_1894-11-22_51_1308/sim_nature-uk_1894-11-22_51_1308_djvu.txt | [body-nature-interest-archive] "have excited considerable interest" present (OCR, columns interleaved; checked against the page image).
- CONFIRMED | and noted, with period dryness, that the cat's "expression of offended dignity… at the end of the first series indicates a want of interest in scientific investigation." | https://archive.org/download/sim_nature-uk_1894-11-22_51_1308/sim_nature-uk_1894-11-22_51_1308_djvu.txt | [body-nature-dignity-archive] present in three interleaved lines; reading order confirmed on the page image of https://www.nature.com/articles/051080a0.pdf.
- CONFIRMED | his falling cat begins each drop with no rotation whatsoever, and turns over anyway | https://en.wikipedia.org/wiki/Falling_cat_problem | [body-marey-norot-wp] "Marey deduced that, as the cat had no rotational motion at the start of its descent, the cat was not \"cheating\" by using the cat handler's hand as a fulcrum."
- CONFIRMED | It can bend, tuck, and counter-rotate its front and back halves - it can change shape. | https://archive.org/download/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18_djvu.txt | [body-cat-counterrotates] Marey p. 716: "le couple résultant de l’action musculaire tend à faire tourner la partie antérieure et la partie postérieure du corps en sens con- traire l’une de l’autre."
- OBSERVED | The body rocks a little and returns precisely to its starting facing - net turn zero, every time. | recreated: node probe3.mjs in /home/liam/.assay-line/claude-1018/the-falling-cat/N2/probe (verify.mjs CAT, the page's wiggle gait theta = 28 deg x 0.5(1 - cos 2 pi t), phi = 0.7) | [body-wiggle-rocks] Body rotation 7.00 deg at a quarter stroke, 14.00 deg at half, 7.00 deg at three quarters, 0.00004 deg at the end: it rocks and returns.
- CONFIRMED | a rigid body with angular momentum cannot help tumbling about its middle axis | https://en.wikipedia.org/wiki/Tennis_racket_theorem | [rel-tennis] "rotation of an object around its first and third principal axes is stable, whereas rotation around its second principal axis (or intermediate axis) is not." The relates note compresses this (spun about the middle axis it tumbles); only its first sentence shows on this page.
- CONFIRMED | the bike on its gyroscope (wrong - it balances with the wheels' spin cancelled) | https://www.ebi.ac.uk/europepmc/webservices/rest/search?query=EXT_ID:21493856&resultType=core&format=json | [rel-bike] Kooijman et al. 2011, Science 332: "We show that neither effect is necessary for self-stability ... we built a bicycle with extra counter-rotating wheels (canceling the wheel spin angular momentum) ... this bicycle automatically recovers to upright travel."
- MINOR | the cat on its tail (wrong - tailless cats land feet-down just the same) | https://en.wikipedia.org/wiki/Cat_righting_reflex | [rel-tailless] "cats without a tail also have this ability". Repair pass: "just the same" overclaims as myth-manx does; the same source says "The tail seems to help". FIXED: relates note now 'tailless cats land feet-down too'.
- CONFIRMED | This page stores no answer and plays back no recording. | public/strata/the-falling-cat/index.html | [check-no-answer] The page script computes physStep() every frame from the prescribed shape; no stored rotation table or recording.
- CONFIRMED | The cat on screen is the live solution of a zero-angular-momentum constraint | public/strata/the-falling-cat/index.html | [check-live-solution] physStep(): "var Om=scl(mv(inv3(Il),b),-1);", then rotates R0 by Om dt.
- CONFIRMED | the body's rotation is solved so that total angular momentum (and linear momentum) stay zero, then integrated | public/strata/the-falling-cat/index.html | [check-lin-mom] build() places the segment centres at -d/2 and +d/2 about the mass centre (equal masses), so linear momentum is zero; physStep solves L = 0.
- MINOR | recomputes every claim two ways that must agree | research/the-falling-cat/verify.mjs | [check-two-ways] "recomputes every claim two ways that must agree": no claim is computed both ways. Checks A-C (flip, two circles, mesh, speed, wiggle, no bend, reverse, curvature) use only the simulator; check D uses only Kane-Scher Eqs. 5 and 8, at a different inertia (J/I 0.25 against the simulator's 0.0583), and D2 integrates Eq. 5 at the beta Eq. 8 gives for psi = pi, so it checks the integrator against the closed form. The cross-check the page describes works (body-two-pieces: 59.43 deg both ways) but is not in the file. FIXED: the check section now says verify.mjs recomputes every number with one of two independent formalisms (the simulator for the first nine rows, Kane & Scher's equations for the last two), and each finds one circle of the waist flips the cat; MINOR, no page correction line.
- CONFIRMED | magnitude of L = 7×10⁻¹⁵ | research/the-falling-cat/verify.mjs | [check-L-row] verify.mjs at ca0306b7ff, and the published copy https://artwaste.land/checks/research/the-falling-cat/verify.mjs (byte-identical) run in an empty directory: exit 0, 10 passed, 0 failed: max/L/ = 7.46e-15. (Claim text: the row "angular momentum during the flip", magnitude of L = 7x10^-15.) The value is the residual of the solve that sets L to zero, so it cannot fail.
- CONFIRMED | one waist-circle, best bend (27.9°) 179.994° | research/the-falling-cat/verify.mjs | [check-circle-row] verify.mjs at ca0306b7ff, and the published copy https://artwaste.land/checks/research/the-falling-cat/verify.mjs (byte-identical) run in an empty directory: exit 0, 10 passed, 0 failed: bend 27.92 deg, net 179.994 deg.
- CONFIRMED | two circles, same bend 0.0° | research/the-falling-cat/verify.mjs | [check-two-row] verify.mjs at ca0306b7ff, and the published copy https://artwaste.land/checks/research/the-falling-cat/verify.mjs (byte-identical) run in an empty directory: exit 0, 10 passed, 0 failed: 0.00 deg.
- CONFIRMED | 121.6575° (spread 1×10⁻⁵) | research/the-falling-cat/verify.mjs | [check-mesh-row] verify.mjs at ca0306b7ff, and the published copy https://artwaste.land/checks/research/the-falling-cat/verify.mjs (byte-identical) run in an empty directory: exit 0, 10 passed, 0 failed: spread 1.18e-5 deg.
- CONFIRMED | net turn vs loop speed same to 3 dp | research/the-falling-cat/verify.mjs | [check-speed-row] verify.mjs at ca0306b7ff, and the published copy https://artwaste.land/checks/research/the-falling-cat/verify.mjs (byte-identical) run in an empty directory: exit 0, 10 passed, 0 failed: 121.6575 vs 121.6575.
- CONFIRMED | one-DOF wiggle (bend in/out) 2×10⁻⁵ ° | research/the-falling-cat/verify.mjs | [check-wiggle-row] verify.mjs at ca0306b7ff, and the published copy https://artwaste.land/checks/research/the-falling-cat/verify.mjs (byte-identical) run in an empty directory: exit 0, 10 passed, 0 failed: 2.11e-5 deg.
- CONFIRMED | circling with no bend 0° | research/the-falling-cat/verify.mjs | [check-nobend-row] verify.mjs at ca0306b7ff, and the published copy https://artwaste.land/checks/research/the-falling-cat/verify.mjs (byte-identical) run in an empty directory: exit 0, 10 passed, 0 failed: 0.00e+0 deg.
- CONFIRMED | reverse the swing negates the turn | research/the-falling-cat/verify.mjs | [check-reverse-row] verify.mjs at ca0306b7ff, and the published copy https://artwaste.land/checks/research/the-falling-cat/verify.mjs (byte-identical) run in an empty directory: exit 0, 10 passed, 0 failed: "fwd.bwd axes anti-parallel, equal magnitude 166.94 deg".
- CONFIRMED | small loops: turn ÷ area → 0.765 (const) | research/the-falling-cat/verify.mjs | [check-curv-row] verify.mjs at ca0306b7ff, and the published copy https://artwaste.land/checks/research/the-falling-cat/verify.mjs (byte-identical) run in an empty directory: exit 0, 10 passed, 0 failed: net/area -> 0.7653.
- CONFIRMED | Kane–Scher Eq. 8, cat inertia J/I=0.25 bend β = 59.4° | research/the-falling-cat/verify.mjs | [check-ks8-row] verify.mjs at ca0306b7ff, and the published copy https://artwaste.land/checks/research/the-falling-cat/verify.mjs (byte-identical) run in an empty directory: exit 0, 10 passed, 0 failed: beta = 59.43 deg; Kane & Scher p. 666 "nearly 60°".
- CONFIRMED | Kane–Scher Eq. 5, one cone revolution ψ = 180.000° | research/the-falling-cat/verify.mjs | [check-ks5-row] verify.mjs at ca0306b7ff, and the published copy https://artwaste.land/checks/research/the-falling-cat/verify.mjs (byte-identical) run in an empty directory: exit 0, 10 passed, 0 failed: psi = 180.000 deg (beta taken from Eq. 8, so this checks Eq. 5 against Eq. 8).
- OBSERVED | → all checks pass | memory/log.d/2026-06-29T2340Z-the-falling-cat.md | [check-all-pass] Log: "node research/the-falling-cat/verify.mjs -> ALL CHECKS PASS (10/10)". Recreated today: verify.mjs at ca0306b7ff, and the published copy https://artwaste.land/checks/research/the-falling-cat/verify.mjs (byte-identical) run in an empty directory: exit 0, 10 passed, 0 failed.
- CONFIRMED | The two formalisms never share a line of code; the only inputs are the cat's geometry and inertia. | research/the-falling-cat/verify.mjs | [check-no-shared-code] kaneScherPsi() and kaneScherAlpha0Beta() use only Math; the simulator uses the linear-algebra kit and CAT. They share no function.
- CONFIRMED | Every number above is derived, not asserted. | research/the-falling-cat/verify.mjs | [check-derived] Every computed cell is printed by verify.mjs; J/I = 0.25 is an input (the paper's measured value), named as such in the row label.
- CONFIRMED | É.-J. Marey, "Des mouvements que certains animaux exécutent pour retomber sur leurs pieds…," Comptes Rendus Acad. Sci. 119, 714–717 (1894) | https://archive.org/download/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18_djvu.txt | [cit-marey] Title as printed ("Note de M. Marey", OCR "Marery"), pp. 714-717, CR 119 no. 18.
- CONFIRMED | summary "Photographs of a Tumbling Cat," Nature 51, 80–81 (22 Nov 1894) | https://api.crossref.org/works/10.1038/051080a0 | [cit-nature] Crossref: "Photographs of a Tumbling Cat", Nature 51 (1308) 80-81, 1894-11; page header "NOVEMBER 22, 1894".
- MINOR | G. Guyou, C. R. Acad. Sci. 119, 717 (1894) | https://archive.org/download/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18/comptes-rendus-hebdomadaires-academie-des-sciences_1894-10-29_119_18_djvu.txt | [cit-guyou] Volume and page right (Note begins p. 717: "Note relative à la Communication de M. Marey ; par M. Guyou", OCR "Guvou"), but the initial is wrong: he is Émile Guyou (fr.wikipedia, and the page's own body text "Émile Guyou"); "G. Guyou" names nobody. N1 did not flag it. FIXED: 'G. Guyou' is now 'É. Guyou' on the page and 'E. Guyou' in the verify.mjs reference comment; MINOR, no page correction line.
- CONFIRMED | L. Lecornu, ibid. 119, 899 (1894) | https://archive.org/download/comptes-rendus-hebdomadaires-academie-des-sciences_1894-11-26_119_22/comptes-rendus-hebdomadaires-academie-des-sciences_1894-11-26_119_22_djvu.txt | [cit-lecornu] "Note de M. L. Lecornu, présentée par M. Appell", pp. 899-900.
- CONFIRMED | T. R. Kane & M. P. Scher, "A dynamical explanation of the falling cat phenomenon," Int. J. Solids Structures 5(7), 663–670 (1969) | https://api.crossref.org/works/10.1016/0020-7683(69)90086-9 | [cit-ks69] Kane T.R., Scher M.P., Int. J. Solids Struct. 5(7) 663-670, 1969-07.
- CONFIRMED | "Human self-rotation by means of limb movements," J. Biomechanics 3(1), 39–49 (1970) | https://api.crossref.org/works/10.1016/0021-9290(70)90049-7 | [cit-ks70] Kane T.R., Scher M.P., J. Biomech. 3(1) 39-49, 1970-01. The tool's DOI MISMATCH is because the claim string omits the authors, which the page gives just before.
- CONFIRMED | (NASA grant NGR-05-020-209) | https://ntrs.nasa.gov/api/citations/19700043129 | [cit-nasa-grant] fundingNumbers NGR-05-020-209; same number in the 1969 footnote (page image).
- CONFIRMED | R. Montgomery, "Gauge theory of the falling cat," Fields Inst. Commun. 1, 193–218 (1993) | https://api.crossref.org/works/10.1090/fic/001/09 | [cit-montgomery] Crossref: Montgomery R., pp. 193-218, in "Dynamics and Control of Mechanical Systems: The Falling Cat and Related Problems", 1993; the scan's first page reads "Fields Institute Communications Volume 1, 1993".
- CONFIRMED | A. Shapere & F. Wilczek, "Gauge kinematics of deformable bodies," Am. J. Phys. 57, 514–518 (1989) | https://api.crossref.org/works/10.1119/1.15986 | [cit-shapere] Shapere A., Wilczek F., Am. J. Phys. 57(6) 514-518, 1989.
- WRONG | A. Jusufi et al., Bioinspir. Biomim. 5 (2010) - tailed vs. tailless, no difference | https://api.crossref.org/works/10.1088/1748-3182/5/4/045001 | [cit-jusufi] Bibliographic details right (Jusufi, Kawano, Libby, Full; Bioinspir. Biomim. 5(4) 045001, 2010), but the gloss "tailed vs. tailless, no difference" is false: the paper is "Righting and turning in mid-air using appendage inertia: reptile tails, analytical models and bio-inspired robots" and finds tails effective in geckos (myth-2010-study). FIXED: the citation and its gloss 'tailed vs. tailless, no difference' are removed from the sources line with the sentence (myth-2010-study); covered by the same Corrected 2026-10-18 line.
- CONFIRMED | H. Essén & A. Nordmark, Eur. J. Phys. 39 (2018) | https://api.crossref.org/works/10.1088/1361-6404/aaac06 | [cit-essen] Essen H., Nordmark A., Eur. J. Phys. 39(3) 035004, 2018.
- CONFIRMED | G. Gbur, Falling Felines and Fundamental Physics (Yale, 2019) | https://en.wikipedia.org/wiki/Falling_cat_problem | [cit-gbur] Further reading: "Gbur, Gregory J. (22 October 2019). Falling Felines and Fundamental Physics. New Haven London: Yale University Press." (Open Library agrees.)
- OBSERVED | Last verified 29 June 2026, when it was written. | memory/log.d/2026-06-29T2340Z-the-falling-cat.md | [gen-verified] Log dated 2026-06-29 records the verifier run before shipping; layer date 2026-06-29T23:30Z.
- CONFIRMED | (added) In 1969 Thomas Kane and M. P. Scher | https://en.wikipedia.org/wiki/Thomas_R._Kane | "Thomas Reif Kane (March 23, 1924 – February 16, 2019) was a professor emeritus of applied mechanics at Stanford University"; the paper's byline is "T. R. KANE and M. P. SCHER", "Department of Applied Mechanics, Stanford University, California".
- CONFIRMED | (added) in Richard Montgomery's "gauge theory of the falling cat" | https://people.ucsc.edu/~rmont/papers/cat.PDF | Scan p. 193: "Gauge Theory of the Falling Cat / Richard Montgomery".
- CONFIRMED | (added) Within the very same volume of the Academy's Comptes Rendus | https://archive.org/download/comptes-rendus-hebdomadaires-academie-des-sciences_1894-11-26_119_22/comptes-rendus-hebdomadaires-academie-des-sciences_1894-11-26_119_22_djvu.txt | Guyou: CR t. CXIX no. 18, p. 717; Lecornu: "C. R., 1894, 2° Semestre. (T. CXIX, N° 22.)", p. 899. Both volume 119.
- CONFIRMED | (added) Kane-Scher Eq. 8 (alpha = 0 closed form) and Eq. 5 (psi over one cone revolution), as the table labels them | https://pentagono.uniandes.edu.co/~jarteaga/geosem/taller7/minicursoJK-Uniandes/robotic%20examples/kane.pdf | Page images pp. 665-666: eq. (5) is dpsi/dtheta; eq. (8) is "2√2(J/I)(1+cos β)^½ = 1−cos β+(J/I)(1+cos β)", the α = 0 case with ψ(2π) = π. Numbering and content match verify.mjs.
- CONFIRMED | (added) Tailless and bobtailed cats - Manx cats | https://en.wikipedia.org/wiki/Manx_cat | "Many Manx have a small stub of a tail, but Manx cats are best known as being entirely tailless".

## Findings
- [fixed] WRONG body-lecornu-picture: the page gave Lecornu the tuck-and-extend picture, which is Guyou's; Lecornu (CR 119 p. 899) showed a turn with fixed shape and inertia. Rewritten in 'What the camera settled', verify.mjs reference comment corrected, Corrected line on the page and in the markdown.
- [fixed] WRONG dek-guyou-lecornu: the markdown dek still gave both Guyou and Lecornu 'the right picture'; now 'Guyou had the right picture ..., and Lecornu another route'; covered by the Lecornu Corrected line.
- [fixed] WRONG body-montgomery: the page dated the gauge-theory recognition to Montgomery 1993; his p. 193 puts it in earlier work (Shapere and Wilczek, Guichardet, his own) and says the 1993 paper applies it to the Kane-Scher cat. Rewritten; Corrected line on the page and in the markdown.
- [fixed] WRONG myth-2010-study: 'a 2010 study comparing tailed and tailless air-righting found no difference' removed from the tail myth; Corrected line on the page and in the markdown.
- [fixed] WRONG myth-2010-study-none: the same sentence, removed with myth-2010-study; covered by the same Corrected line.
- [fixed] WRONG cit-jusufi: the Jusufi et al. 2010 citation and its gloss 'tailed vs. tailless, no difference' removed from the sources line; covered by the same Corrected line.
- [fixed] MINOR dek-ks-nasa: markdown dek 'proved the half-turn' now 'showed ... how one cycle can overturn the cat'.
- [fixed] MINOR body-ks-two-halves-proved: 'proved it exactly' now 'showed that, with the right bend, one full cycle ... makes the body overturn'; 'precisely a half-turn is not a coincidence' now 'can produce a half-turn is not a quirk'.
- [fixed] MINOR dek-verify-two-ways: markdown body now says each number is recomputed by one of two independent formalisms; verify.mjs header comment no longer says they are checked against each other.
- [fixed] MINOR check-two-ways: check section wording now says which rows each formalism computes, and that each finds one circle flips the cat.
- [fixed] MINOR body-century-handshove: 'for a century people insisted' now 'some people believed'.
- [fixed] MINOR body-century-marey: same sentence as body-century-handshove.
- [fixed] MINOR body-2799-flip: 'four thousandths' now 'six thousandths' of a degree.
- [fixed] MINOR body-marey-1029: 'On 29 October 1894' now 'In October 1894'.
- [fixed] MINOR body-dozen: 'a dozen times' now 'some twenty times'.
- [fixed] MINOR body-guyou-engineer: 'the engineer' now 'the naval officer'.
- [fixed] MINOR cit-guyou: 'G. Guyou' now 'É. Guyou' (page) and 'E. Guyou' (verify.mjs comment).
- [fixed] MINOR body-1969-rigor: 'What 1969 added' now acknowledges 'an earlier model by Rademaker and ter Braak'.
- [fixed] MINOR myth-manx: 'right themselves just as well' now 'right themselves too'.
- [fixed] MINOR rel-tailless: relates note to the-bike-that-rights-itself 'tailless cats land feet-down just the same' now 'tailless cats land feet-down too'.
- [fixed] MINOR foot-consensus: 'the scholarly consensus is' now 'the best current view is'; sources line 'Consensus that' now 'That real cats probably blend mechanisms'.