Talk:Opticks

Equations

In the "Opticks and the Principia" section, the following is written: "It does not prove its propositions by the use of ratios or equations." Newton's Principia, however, does not contain any equations. He used only ratios in that book.Lestrade (talk) 14:48, 3 August 2008 (UTC)Lestrade

the text and correction are both inaccurate. ratios and equations are mathematical constructs. the entire deductive framework of the principia is cast in geometric form, using geometric arguments that shadow the calculus newton had already developed. newton then applied mathematics ("equations and ratios") to available astrometric data to calculate the orbits of the moon and planets and the trajectories of comets, all substantiating at very different astronomical scales the "universality" of gravitation. Drollere (talk) 19:19, 26 February 2018 (UTC)

Numerous Errors

there are several problems with this page, which should have merited a flag from the editors:

• "multiverse" is a modern physics term with a specific denotation. to say newton anticipated this concept is a claim ranking with democritus predicting the bohr atom or galileo the theory of relativity. newton merely speculates that there may be *worlds* (physical bodies, as is clear from the context) where physical processes quite alien to our own experience may operate. one might better say he anticipated black holes, but that would be equally silly. newton explicitly and conventionally conceived of a single universe unified in space and time. the "multiverse" claim must be deleted.

• there's no description of the contents of newton's first publication (1671/2) of his researches in the (then new) royal society transactions. newton did not publish the opticks in an english edition because english was widely popular on the continent but because it would immediately restore his domestic reputation in the vernacular audience and urinate on the legacy of robert hooke. the first (english) edition contains two appendices written in latin for the scholarly audience, and the latin edition appeared two years later: so much for the ascendance of english over latin in scientific discourse. there was instead a growing preference for contemporary speech that first appears in vernacular bibles and supported a very general revolt against clerical and doctoral authority known as the enlightenment.

• newton was entirely correct that chromatism is inherent and unavoidable in any form of refraction. dollard did not prove newton wrong; he found a partial remedy through the use of multiple lenses with compensatory dispersion characteristics. even the best modern achromats do not eliminate chromatism; they simply push it into the spectrum extremes where it is not readily visible. the more interesting point, omitted in the article, is that newton's conclusion led him to invent the newtonian reflector, which is inherently achromatic. Tyndall was merely showboating while shooting from the hip.

• there are numerous errors of basic interpretation. "refrangibility" is not a fixed property but changes depending on the refracting medium; it's the *relative differences* in refrangibility that produce the spectrum dispersion. "white" light is indeed made to appear as a color because it is darkened (absorbed) by matter; newton's contribution was to explain *how* this darkening occurred, as the absorption or reflection of some "colors" of light more than others. descartes's scientific method was not "deduction from first principles" (that's his epistemology), it was the undisciplined induction of first principles from specific phenomena that newton savaged in his critique of cartesian vortices. newton himself reasoned deductively from first principles when he declared that universal gravitation must obey an inverse square form, then showed how this first principle would explain many different phenomena. and the continental animus against newton, though centered in the cartesian partisans, extended to the many different inductive conjectures that populated the learned natural sciences at the time and apparently was sustained by the clumsiness of contintental naturalists in replicating newton's experimental methods (replications that were made before the royal society audience by desaguliers in 1722).

• "color" is not the visible manifestation of wavelength (which is commonly used to index it) but of "refrangibility" (refractive index); wavelength is simply the conventional optical preference to the alternative wave number (frequency) which is actually a more relevant metric to use for refraction (wavelength being the better metric for diffraction).

• on that note, nothing is said about newton's experiments in the color mixtures of light, his use of a color circle to explain the geometric weighting of the mixtures, his demonstration that pigment lightness (whiteness/grayness) is simply the perception of luminance and is not inherent to the colored materials, his careful avoidance of the "stimulus error" by stating color is only an aspect of the "sensorium", etc. these are among the earliest and astonishingly insightful examples of psychophysical experimentation. his insights were directly adopted by maxwell, grassmann and helmholtz in the foundational researches of 19th century colorimetry. the amusing detail is that helmholtz first declared he had disproved newton, then later with better experimental methods admitted he was wrong and newton was correct. Drollere (talk) 16:15, 26 February 2018 (UTC)

Consistent spelling

The article seems to mix American and British English spellings. Jaiganesh.kumaran (talk) 07:57, 17 January 2024 (UTC)