Sbagliando s'impera

Baeyer, Hans Christian von (2003). Information: The New Language of Science. London: Phoenix. 2003.

Non sono sicuro di aver capito tutto. Mentre sulla teoria classica dell’informazione mi sento abbastanza sicuro (in fin dei conti il mio Shannon l’ho letto), la parte dedicata alla Quantum Information mi mette in difficoltà. Ma apparentemente sono in buona compagnia:

If anybody says he can think about quantum physics without getting giddy, that only shows he has not understood the first thing about them. [Niels Bohr]

If quantum mechanics hasn’t profoundly shocked you, you haven’t understood it yet. [Niels Bohr]

If someone says that he can think or talk about quantum physics without becoming dizzy, that shows only that he has not understood anything whatever about it. [Murray Gell-Mann]

I think it is safe to say that no one understands quantum mechanics. Do not keep saying to yourself, if you can possibly avoid it, ‘But how can it possibly be like that?’ because you will go down the drain into a blind alley from which nobody has yet escaped. Nobody knows how it can be like that. [Richard Feynman]

Per non parlare dei dubbi di Einstein.

Il libro di von Baeyer è un tour de force, e mi sento di raccomandarlo vivamente, anche se non tutto mi sembra egualmente convincente. Ma è certo che von Baeyer ha il raro dono della divulgazione (quello che gli anglosassoni chiamano, capovolgendo la nostra prospettiva, public understanding of science), e sono rimasto impressionato dal modo fresco e nuovo di illustrare e far comprendere cose che già conoscevo. Basti per tutti la spiegazione del “problema di Monty Hall” [pp. 69-72].

Von Baeyer fa un uso ampio ed efficace di quelle che Daniel Dennett chiama intuition pumps.

Sotto il profilo filosofico (che è quello in cui, tutto considerato, mi sento più a mio agio), mi sembra che von Baeyer sia vicino al punto di vista di Bohr, che affermava:

“Our task is not to penetrate into the essence of things, the meaning of which we don’t know anyway, but rather to develop concepts which allow us to talk in a productive way about phenomena in nature.”
“There is no quantum world. There is only an abstract quantum physical description. It is wrong to think that the task of physics is to find out how nature is. Physics concerns what we can say about nature.” [citato a p. 65]

Von Baeyer aderisce apparentemente alla soluzione proposta da Anton Zeilinger:

Its crucial, underlying assumption is Bohr’s proclamation that physics in general, and quantum mechanics in particular, do not describe the world itself, only what we are able to say about it. Bohr demands that we wake up from the spell of Democritus – the illusion that we can come to grips with the objective material world, without acknowledging, or even trying to understand, the mediating role of information. We never see a chair, Bohr would say: we receive senso impressions that give us information which our brains somehow process into the idea (an Aristotelian ‘Form’) of chair. We don’t see, or detect, or measure an atom: we gather information about the atom and encode it in a mathematical construct called a wave function, which enables us to make predictions about information we may gather in future experiments. [p. 227]

Why does nature seem granular, discontinuous, quantized into discrete chunks like sand – instead of smooth and continuous like water? The answer is that while we have no idea how the world is really arranged, and shouldn’t even ask, we do know that knowledge of the world is information; and since information is naturally quantized into bits, the world also appears quantized. If it didn’t, we wouldn’t be able to understand it. It’s both as simple, and as profound, as that. [p. 229]

Ecco, io non so voi, ma a me questa spiegazione ha lasciato con un grande senso di pace interiore, “un grande senso di dolcezza…”. LA sensazione di essermi avvicinato un po’ a una verità.

E mi è venuta in mente una cosa molto personale. Io sono molto miope, pochi possono immaginare quanto. E fin da bambino, senza occhiali, nella penombra, quello che vedevo (e vedo) mi appariva granulare, come dipinto da Seurat. La spiegazione di von Baeyer– nell’unificare teoria quantistica e teoria dell’informazione – risuona in me con questa sensazione consueta.