Dioptrics

[By this] perplexity he achieved that small result which had escaped the crude instrument of Gemma Gemma Frisius (1508–1555), a Dutch physician, mathematician, and master instrument maker. and the attention of a single, solitary man. And I myself, in the optical part of my astronomy, brought forth witnesses for refractions as reserves for Brahe Tycho Brahe (1546–1601), the preeminent observer whose data Kepler used to derive the laws of planetary motion., drawn from antiquity, and therefore complete and untainted.

I hear that Doctor Helisæus Röslin Helisaeus Röslin (1545–1616) was a German physician and astronomer who often engaged in friendly but sharp debate with Kepler. has proposed a problem for me to solve concerning the sun being seen by the Dutch in the northern lands fourteen days earlier than it should have been Original: "à Batavis in septentrionali Terra viso." This refers to the "Nova Zembla phenomenon" of 1597, where atmospheric refraction caused the sun to appear above the horizon nearly two weeks early during a polar expedition.. I have not seen his book because of these disturbances A reference to the political and religious unrest in the Holy Roman Empire during the early 17th century.. However, I advise that this question was resolved by me through the refractions of the air in The Optical Part of Astronomy, Chapter 4, Number 9, page 138.

Pena gave the second place to the doctrine concerning the truly eccentric paths of the planets Orbits that are "off-center" or do not share a common center with the Earth.; and he did so rightly. Optics possesses the firmest arguments for these. Only this must be guarded against: lest that which happened to the ancients happen to us—that while trusting too securely in one eye (that of Optics) for the perception of this planetary orbit, we close the other eye (that of Physics). Thus, by attributing solely to optics what ought to have been granted equally to the reasoning of both Optics and Physics, we might again miss the mark. On this matter, see my Optical Part of Astronomy and my Commentaries on the Motions of Mars Kepler’s Astronomia Nova (1609), in which he published his first two laws of planetary motion..

In the third place, Pena examines the question of the order of the planets from the perspective of Optics. He does not reason poorly based on Aristotle: if the Earth indeed stands fixed in its place, it is not likely that the Sun, Venus, and Mercury—in three distinct orbits of unequal size—would travel around in an equal period of time. Rather, it is more consistent—as pleased Martianus Capella, Campanus, and Brahe, and as Galileo demonstrates most evidently below—that if the Sun is being carried, those others are carried in a single orbit, and the Sun (like the axle of wheels) is surrounded by the epicycles Small circles whose centers move along the circumference of a larger circle. of Venus and Mercury as if by the rims of wheels. Indeed, it is most probable—as Copernicus held, and as that most ancient Samian philosophy Referring to the school of Pythagoras of Samos, who were thought by the Renaissance to have held heliocentric views. held so many centuries ago—that the Sun stands fixed in the center; and around it, not only Mercury and Venus at their own times, but even the Earth itself with the Moon as its companion, travel in an annual motion, along with the other three planets in their respective periods.

Here again, however, Pena [extricates] himself from the briars, though with some loss of truth...