Did the law hold in the sequence?

The inclined plane sits in the corner of the workroom, its groove worn smooth by a hundred bronze balls. The marks for the quarter-pulsations are still faintly visible on the timber. On the night of the 14th, with the lamp guttering, the final trial was completed. The ratios held: the distance traversed in successive equal times increased as the odd numbers from unity. The law is in the sequence of distances, a truth contained entirely within the measured intervals between the marks.

This measurement, this simple progression of spaces, is the argument. Yet the Dialogo must speak of harmonies, of cosmic circles, of accommodating this finding within a language of perfection that the schools will recognize. The core discovery - that motion itself has a quantifiable, constant character - is buried in the third day’s discourse, a necessary foundation for the larger, more palatable argument about the heavens. One builds the cathedral to draw the eye, while the true keystone rests in the plain geometry of the foundation, unseen.

The prior belief is that celestial and terrestrial physics are distinct. The observation from the plane is that acceleration is uniform and mathematical. The prior cannot admit the observation, so the observation is placed where it will not immediately offend - in the supporting structure, where only those who build will look. It is not hidden, but it is not proclaimed. It sits, waiting for the prior to weaken.

The instrument is not mistaken. The groove is straight, the ball is true, the water clock measures equal times. The observation updates the prior; the prior does not adjust the marks on the wood. Let them debate the epicycles of Jupiter’s moons. The law of the falling body is here, in these mundane intervals, already written. It will be decades before someone reads the footnote and understands that the cathedral was built for the keystone, not the other way around.