La scienza avanza facendo capriole

Revolutions as Changes of World View – The Structure of Scientific Revolutions: 50th Anniversary Edition di Thomas S. Kuhn

Vuoi capire come avanza la scienza? Pensa ad un’esperienza gestalt.

4676_ea6979872125d5acbac6068f186a0359

Quel fenomeno per cui, per esempio, nello stesso disegno è possibile vedere cose differenti…

… In their most usual form, of course, gestalt experiments illustrate only the nature of perceptual transformations. They tell us nothing about the role of paradigms or of previously assimilated experience in the process of perception. But on that point there is a rich body of psychological literature, much of it stemming from the pioneering work of the Hanover Institute…

L’innovatore è colui che percepisce cio’ che nessuno vede.

Provate a indossare gli occhiali invertiti. Prima tutto sembra strano, non vi raccapezzate. Ma poi, piano piano, prenderete le misure del nuovo mondo capovolto e lo abiterete con disinvoltura. Non solo: salteranno al vostro occhio aspetti nuovi che prima non vedevate…

… An experimental subject who puts on goggles fitted with inverting lenses initially sees the entire world upside down. At the start his perceptual apparatus functions as it had been trained to function in the absence of the goggles, and the result is extreme disorientation, an acute personal crisis. But after the subject has begun to learn to deal with his new world, his entire visual field flips over, usually after an intervening period in which vision is simply confused…

Entrare in un nuovo mondo, ecco cosa significa cambiare paradigma scientifico.

Nel nuovo mondo percepirete cose nuove che prima non vedevate. Dubbio: non è che il paradigma indirizza la visione?…

… Surveying the rich experimental literature from which these examples are drawn makes one suspect that something like a paradigm is prerequisite to perception itself….

La scienza cambia non per cumulo di conoscenze ma per slittamenti di percezione.

L’unico cumulo è quello delle anomalie che favoriscono il cambio di paradigma.

Detto questo, il gestalt non è ancora un’analogia perfetta del cambio di paradigma: nel gestalt le percezioni possono viaggiare avanti e indietro

…. The subject of a gestalt demonstration knows that his perception has shifted because he can make it shift back and forth repeatedly while he holds the same book or piece of paper in his hands. Aware that nothing in his environment has changed, he directs his attention increasingly not to the figure (duck or rabbit) but to the lines on the paper he is looking at… With scientific observation, however, the situation is exactly reversed. The scientist can have no recourse above or beyond what he sees with his eyes and instruments…

Quando uno scienziato entra in un nuovo paradigma la marcia indietro è molto difficile.

L’esempio del copernicano

… Copernicanism does not say, “I used to see a planet, but now I see a satellite.” That locution would imply a sense in which the Ptolemaic system had once been correct. Instead, a convert to the new astronomy says, “I once took the moon to be (or saw the moon as) a planet, but I was mistaken.”…

Esempio: Sir William Herschel scopre Urano.

Prima, tutti guardavano il pianeta dicendo “ecco una stella“…

… On at least seventeen different occasions between 1690 and 1781, a number of astronomers, including several of Europe’s most eminent observers, had seen a star in positions that we now suppose must have been occupied at the time by Uranus…

WH pasticcia sul suo telescopio e dice “non è una stella semplice, è una cometa”. Poi apporta altre modificazioni e dice “forse è un pianeta”…

… Herschel, when he first observed the same object twelve years later, did so with a much improved telescope of his own manufacture. As a result, he was able to notice an apparent disk-size that was at least unusual for stars. Something was awry, and he therefore postponed identification pending further scrutiny. That scrutiny disclosed Uranus’ motion among the stars, and Herschel therefore announced that he had seen a new comet! Only several months later, after fruitless attempts to fit the observed motion to a cometary orbit, did Lexell suggest that the orbit was probably planetary…

Le anomalie riscontrate da WH cambiarono la percezione: molte stelle sparirono e molti pianeti comparvero…

… When that suggestion was accepted, there were several fewer stars and one more planet in the world of the professional astronomer. A celestial body that had been observed off and on for almost a century was seen differently after 1781 because, like an anomalous playing card, it could no longer be fitted to the perceptual categories (star or comet) provided by the paradigm that had previously prevailed…

Il paradigma ti cambia l’occhio.

Entra il paradigma di Copernico e vedi movimento dove c’era fissità

… Can it conceivably be an accident, for example, that Western astronomers first saw change in the previously immutable heavens during the half-century after Copernicus’ new paradigm was first proposed?…

L’ “occhio cinese” – restio alla fissità – vedeva a occhio nudo cio’ che noi non vedevamo con i telescopi…

… The Chinese, whose cosmological beliefs did not preclude celestial change, had recorded the appearance of many new stars in the heavens at a much earlier date. Also, even without the aid of a telescope, the Chinese had systematically recorded the appearance of sunspots centuries before these were seen by Galileo and his contemporaries….

Dopo Copernico gli astronomi cominciarono a vivere in un mondo differente sotto un cielo differente.

***

Altro caso: l’elettromagnetismo.

Le particelle che prima rimbalzavano o “cadevano” ora vengono “respinte”…

… During the seventeenth century, when their research was guided by one or another effluvium theory, electricians repeatedly saw chaff particles rebound from, or fall off, the electrified bodies that had attracted them. At least that is what seventeenth-century observers said they saw, and we have no more reason to doubt their reports of perception than our own. Placed before the same apparatus, a modern observer would see electrostatic repulsion (rather than mechanical or gravitational rebounding), but historically, with one universally ignored exception, electrostatic repulsion was not seen as such until Hauksbee’s large-scale apparatus had greatly magnified its effects…

Altro caso: Lavoisier. Dove gli altri vedevano aria de-fligistizzata, lui vede ossigeno…

… Shifts of this sort are not restricted to astronomy and electricity. We have already remarked some of the similar transformations of vision that can be drawn from the history of chemistry. Lavoisier, we said, saw oxygen where Priestley had seen dephlogisticated air and where others had seen nothing at all. In learning to see oxygen, however, Lavoisier also had to change his view of many other more familiar substances. He had, for example, to see a compound ore where Priestley and his contemporaries had seen an elementary earth, and there were other such changes besides. At the very least, as a result of discovering oxygen, Lavoisier saw nature differently…

Altro caso Galileo: dove gli altri vedono un corpo che tenta disperatamente di cadere ostacolato da una corda, lui vede un pendolo perpetuo…

… Since remote antiquity most people have seen one or another heavy body swinging back and forth on a string or chain until it finally comes to rest. To the Aristotelians, who believed that a heavy body is moved by its own nature from a higher position to a state of natural rest at a lower one, the swinging body was simply falling with difficulty… Galileo, on the other hand, looking at the swinging body, saw a pendulum, a body that almost succeeded in repeating the same motion over and over again ad infinitum. And having seen that much, Galileo observed other properties of the pendulum as well and constructed many of the most significant and original parts of his new dynamics around them…

Il nuovo occhiale galileiano consente di elaborare la nuova dinamica dei corpi. Sia Galileo che gli aristotelici percepiscono lo stesso fenomeno ma lo vedono in modo differente.

Si potrebbe minimizzare parlando di semplici interpretazioni differenti

… Many readers will surely want to say that what changes with a paradigm is only the scientist’s interpretation of observations… On this view, Priestley and Lavoisier both saw oxygen, but they interpreted their observations differently; Aristotle and Galileo both saw pendulums, but they differed in their interpretations of what they both had seen…

Ma dire che si “vedono cose diverse” è più esplicativo, si rende conto meglio della rivoluzione in atto di lì a poco, delle nuove scoperte apportate dal nuovo occhiale. Non c’è interpretazione diversa ma visione diversa. Si realizza una sorta di incomunicabilità tra il prima e il dopo…

… What occurs during a scientific revolution is not fully reducible to a reinterpretation of individual and stable data. In the first place, the data are not unequivocally stable. A pendulum is not a falling stone, nor is oxygen dephlogisticated air….

Ancora oggi l’uomo della strada, ingenuo copernicano, non comprende appieno l’errore del tolemaico. Lo pensa come un errore di ortografia più che come un modo diverso di percepire gli stessi identici fenomeni.

Così come non c’è la scoperta di qualcosa in più, non ci sono “dati fissi” suscettibili di reinterpretazione, non c’è una base comune

… the transition from constrained fall to the pendulum or from dephlogisticated air to oxygen is not one that resembles interpretation. How could it do so in the absence of fixed data for the scientist to interpret?…

Per questo parliamo di incommensurabilità dei paradigmi.

Oltretutto: ciò non toglie che vi sia anche un lavoro di reinterpretazione. Ma resta ben distinto dal cambio di paradigma…

… None of these remarks is intended to indicate that scientists do not characteristically interpret observations and data. On the contrary, Galileo interpreted observations on the pendulum, Aristotle observations on falling stones, Musschenbroek observations on a charge-filled bottle, and Franklin observations on a condenser… But that interpretive enterprise—and this was the burden of the paragraph before last—can only articulate a paradigm, not correct it…

Altro esempio? Dalton, con la sua teoria atomica, ridusse la chimica alla fisica conoscendo ben poco di chimica.I chimici, fino ad allora, interpretavano i “composti” come amalgami di particelle “affini”. La nuova proposta atomica di Dalton fu una rivoluzione, un modo diverso di vedere le stesse cose, un linguaggio diverso di descrivere gli stessi fenomeni. Dalton non scoprì nuove realtà ma fornì gli occhiali per rivoluzionare la disciplina e scoprirle in seguito.

***

Morale: c’è qualcosa di non neutrale nell’esperienza. Noi indossiamo occhiali…

… But is sensory experience fixed and neutral? Are theories simply man-made interpretations of given data? The epistemological viewpoint that has most often guided Western philosophy for three centuries dictates an immediate and unequivocal, Yes! In the absence of a developed alternative, I find it impossible to relinquish entirely that viewpoint. Yet it no longer functions effectively, and the attempts to make it do so through the introduction of a neutral language of observations now seem to me hopeless…

L’esperienza è veicolata dal paradigma…

… Far more clearly than the immediate experience from which they in part derive, operations and measurements are paradigm-determined. Science does not deal in all possible laboratory manipulations…

Morale: il sapere scientifico è olistico, mai riduzionista.

Noi conosciamo un contesto, mai un singolo fatto. E’ la tesi Duhem-Quine.

Tesi Duhem-Quine: le ipotesi non sono mai verificabili isolatamente…… All of this may seem more reasonable if we again remember that neither scientists nor laymen learn to see the world piecemeal or item by item. Except when all the conceptual and manipulative categories are prepared in advance—e.g., for the discovery of an additional transuranic element or for catching sight of a new house—both scientists and laymen sort out whole areas together from the flux of experience…

I paradigmi condizionano le nostre verifiche. Ipotesi e verifiche non sono mai indipendenti.

Annunci

Un pensiero riguardo “La scienza avanza facendo capriole”

Rispondi

Inserisci i tuoi dati qui sotto o clicca su un'icona per effettuare l'accesso:

Logo WordPress.com

Stai commentando usando il tuo account WordPress.com. Chiudi sessione / Modifica )

Foto Twitter

Stai commentando usando il tuo account Twitter. Chiudi sessione / Modifica )

Foto di Facebook

Stai commentando usando il tuo account Facebook. Chiudi sessione / Modifica )

Google+ photo

Stai commentando usando il tuo account Google+. Chiudi sessione / Modifica )

Connessione a %s...