Will Taking Maalox Produce A Black Stool?

Ottica: Cannocchiale e Aberrazione sferica

Sommario:

+ Introduzione
+ Riflessione
+ Rifrazione
+ Diffrazione
– Aberrazione sferica e Cannocchiale
       Cannocchiale
       Microscopio
       Aberrazione spherical
Aspherical
+ Dispersion and Newtonian
+ + luminiferous ether
Birefringence and Polarization Interference
+
+ Rainbow

The telescope

beginning of the seventeenth century in Holland the first telescopes were built. Actually had more use of terrestrial telescope that astronomical instrument: their poor resolving power, and the fact that they were made by "cowards" Mechanical (To paraphrase Manzoni), or artisans spectacle, meant that the academic community tends to reject these objects as well as being precisely extraction "plebeian," distorts the images and did not give any guarantee of scientific rigor.

Galileo Galilei is considered in many ways the father of modern science, and this is especially true with regard to astronomy: he studied the problems of optical telescopes, not disdain to make the lenses required for its own account (not manual tasks employment were considered worthy by the scholars of his time) and in 1609 finally built a telescope of sufficient quality, it pointed skyward.



Certainly this first telescope of Galileo was imperfect, but allowed him to carry out a campaign of systematic observations which are included in the publication, in 1610, the book "Starry Messenger," where exactly " announces "his findings. Discoveries recently:

- The Moon is not perfectly round: has "mountains" that under conditions of light grazing (eg lunar dawn) give rise to a light-shade boundary line jagged. This refutes the old theory that all heavenly bodies must be perfectly spherical.

- Jupiter has four satellites: another refutation of the ancient theories according to which the circular motion of all celestial bodies must be centered on Earth.

- The Milky Way is made up of myriads of stars, and the rest of the universe contains far more than had ever been seen before.



(From left: the Moon in an original design of Galileo, published in his "Starry Messenger", a photo-NASA Jupiter with his spot, from the satellites Io, Europa, Ganymede and Callisto, and finally, again from the site of NASA, the Milky Way).

... and this is just the beginning! In later writings, Galileo will be exhibiting its comments on Mercury and Venus, whose steps can be justified only by admitting their rotation around the Sun, not Earth (further refutation of the geocentric), describe the "strange form" of Saturn (there Huygens will take to identify this strange shape, with the famous rings).

Galileo was also the first to observe the planet Neptune, in December 1612. By coincidence, at that moment the apparent motion of Neptune was almost none, since he was just "reverse" their march to begin a process of "motion retrograde. " Galileo then exchanged it for a fixed star ... in short, Neptune will have to wait until 1846 to finally be discovered!

course, after listing all these scientists were trying to get a telescope, even if it was not easy, for there were very few craftsmen capable of building quality specimens. Moreover, even the Princes and Nobles, curious, wanted to make their views known: and, of course, between Princes and astronomers ... were the first to take precedence! ▲

the microscope

Negli anni successivi un altro strumento iniziava a svelare un mondo totalmente nuovo: il Microscopio, che consentiva di esplorare le cose piccole, invisibili a occhio nudo.
Chi aveva mai sospettato l'esistenza dei batteri? Forme di vita, indubbiamente (si muovono, mangiano, si moltiplicano)... possibile che nella Creazione fossero stati considerati anche questi esseri minuscoli, di cui dall'inizio del mondo non era mai stata neanche sospettata l'esistenza?

Insomma il Creato stava dimostrando di essere molto più vasto e complesso (sia nel grande che nel piccolo) di quanto si fosse immaginato fino al secolo precedente!    ▲   

Spherical aberration

Telescopes and microscopes ... two instruments that have many things in common, and that at that time suffered from the same flaws: as we find new ways to get better lenses, the focus remained a perfect chimera. It was the need to obtain better tools to push many scientists to work on optics.

One of the causes of errors in optical instruments was the so-called "spherical aberration": the classic biconvex lenses, bounded by two spherical surfaces, did not allow a perfect focus.



The parallel rays, from left, are refracted by convex lens, but not all converge in the same place as they should. Things improve a bit 'using plano-convex lenses:



refracted rays converge a bit' better, but without achieving perfection. It was soon discovered that this phenomenon becomes less, the greater the focal length lens (the distance from the lens to the point of convergence of rays refracted), but at long focal lengths mean instruments in large proportion. In fact, it came like this also tools built by Johannes Hevelius (1611-1687): 45 meters in length!    ▲   



Lenti asferiche

La soluzione definitiva al problema dell'aberrazione sferica si ebbe, una volta note le leggi di rifrazione, con la costruzione delle lenti "asferiche": lenti le cui superfici non sono più a forma di calotta sferica, ma hanno un profilo a forma di parabola o di iperbole.

I primi tentativi di costruzione di questo nuovo tipo di lenti (a parte il matematico arabo Ibn Sahl che ci lavorò prima dell'anno 1000 ma di cui non si sapeva niente nell'Europa del XVII secolo) sono ascrivibili a Cartesio e a Constantijn Huygens (il padre del Christiaan di cui abbiamo già parlato nella puntata precedente, e di cui parleremo ancora) intorno agli anni 1620-1630. Per ottenere lenti asferiche di qualità si dovette però aspettare l'opera di Francis Smethwick, che ne produsse a partire dal 1666.

Per quanto i telescopi fabbricati con queste nuove lenti fossero sensibilmente migliori di quelli costruiti con lenti tradizionali, un alone variamente colorato si veniva sempre a creare all'intorno dei punti luminosi (ovvero intorno a ciascuna stella), riducendo il potere di risoluzione dello strumento. Anche il microscopio risentiva di problemi analoghi, e a lungo andare il problema cominciava ad essere considerato irrisolvibile.

Luckily ... Next Chapter: Dispersion and Newtonian