Chiara Marletto

Cynic Alter-Ego: “Nice SF. So now we want to explain nature without equations of motion. I will go back to study my Aristotle book. Science fiction in academy goes on. After the multiverses we go for no equations... in addition to title "Beyond Quantum Computation"... still there no real quantum computer (apart from some big claims but nothing more than 50qubits doing little tasks) and very from a real one .... but they already speak about beyond quantum computing... how these people can have success , it is a shame.”

Constructor Theory Fan: The amount of comments like this is astounding. You know you can literally read the paper pre-prints on the website, right? Nobody is suggesting to do away with equations of motions - i.e. dynamics - as a fundamental tool in the physics arsenal. The point of this theory as far as I can see, on a very rough level, is to provide a mechanism for the introduction of counterfactual knowledge into physical theories. By doing so you can reduce the size of the admissible solution space when it comes to exploring those new theories. It's not that magical or complicated... but again understanding this would require approximately 30-40 seconds of googling followed by maybe 10-15 minutes of light reading, so it is understandable that people might struggle with that.”

Cynic Alter-Ego: Well, Deutsch and Marletto claim to have new physics . A new theory , deeper than quantum mechanics, that allow to deduce things like thermodynamics. From this new physics in their papers there is no trace how you deduce Schrödinger’s or Einstein’s equations from these new principles. Neither trace on how you are expected to solve the measurement problem, so mysterious what is deeper than quantum mechanics. Neither rigorous derivation of chaos, and this makes it quite mysterious how they can derive thermodynamics. You can all ignore me but I'll warn you all here: Constructor Theory is (another) dead end like String Theory. It is asking us to be Oracles. We just cannot know what is possible and what is impossible until we know the physical laws. Even if the laws are written in Holy Granite Marble in terms of "can" and "can't" we cannot discover them efficiently without a deeper theory that derives for us what is possible to construct and what cannot be constructed (a theory of the Marble Itself, so to speak). So at best, CT is like a symbiotic living off a deeper sort of theory of physics or metaphysics, so CT is not fundamental, it is post-fundamental. But that's just MHO. Seems to me, much like QIT, this bunch of principles of CT is useful as a window onto fundamental physics, a new way of seeing the world, and that's highly valuable, but in the end it will still lead to a dead end, much like the "It from Bit" meme. It is still not clear to anyone whether a physical theory of everything, or even a sweeping neo-positivist instrumentalist view (Sabine Hossenfelder), can do without some metaphysics. To me, just my opinion, a physics theory of everything is a misnomer, it can only ever be a theory of everything physical which will always beg the question, "are there realities which cannot be described by physics and require some sort of metaphysics?" And as Noam Chomsky would say, that means things that are not in-principle mathematically describable (because once you can mathematicize a phenomena it really "becomes physics" --- you tack it on to what you now redefine as "physics".) Consciousness (the Chalmers definition at least, not the Minsky-Dennett impoverished instrumentalist definition) is a candidate for a phenomenon we "detect" that is not in-principle mathematically describable.”

Constructor Theory Fan: “Seems to me it's not true that Constructor Theory has no dynamics. You cannot get any emergence of phenomena not implicit in the system from foundations. Principle 1 of Constructor Theory says ‘Laws of physics are expressible entirely in terms of statements about which physical transformations are possible and which are impossible, and why.’ Any transformation is dynamics. What would be ‘emergent’ in Constructor Theory is time & length scale and particular laws like causality (special relativity) and the like. All that has to be implicit though in the principles. Laws cannot emerge as novelties. People misunderstand the whole idea of emergent complexity in this way. What is genuine novel emergence cannot be physical law baked into the ‘marble’, it can only be a pattern that persists for limited time, and thus is merely an approximate high-level ’aw-like’ feature of certain constrained systems (e.g., the biological "laws" of genetics, or mitosis, etc --- they're not fundamental laws of physics nor Constructor Theory because if there were no biological entities (which is conceivable) then mitosis etc., would not exist).”

Cynic Alter-Ego: “It might not even be possible to ever "scientifically prove" that the Chalmers-Gödel idea of consciousness - if we suppose it's what our subjective consciousness instantiates - is mathematically describable or not. Note to prove it so, without circularity, requires you cannot assume consciousness emerges from just brain processes, nor can you assume it doesn't. In other words it cannot be accomplished by pure logic (logic can only ever tell you the consequences of your axioms, so your axioms implicitly include an assumption about the consequences of any derivation, if you overlay a phenomenal interpretation). That in turn means you need a theory along with empirical data for a "scientific proof." That's a touch of why such a "scientific proof" might be impossible: what empirical data is ever going to be able to "prove" (when attached to a theory) that a phenomenon is mathematically describable or not? For one thing, that presumes we know, or have a meta-theory, of what is "mathematically describable." At present we do not, and likely never will. We generally only find out a complex system is mathematically describable when we find an effective description/model. We’re really in a new dark age of Stupidity.”

Constructor Theory Fan: (*sigh*)

SF = Speculative Fiction.… (plus d'informations)

Chiara Marletto is a delight. A theoretical physicist, she has written a book that makes it stimulating, varied, exciting and real. Plus, it is a genuine, innovative gamechanger. Plus, every chapter begins with a story she has made up, because her father was a fascinating storyteller. On their daily walks, he would make up stories about anything and everything they saw along the way. And passed this talent and tradition on. And one more thing. Marletto is Italian. English is not her first language. All these things combine to make The Science of Can and Can’t an unexpected treasure.

The issue she tackles is that physics has prescribed itself into a dead end. Not for the first time, Man thinks he has discovered everything that is discoverable. At the end of the 19th century, it was recommended that the patent office be shut down, as everything that could possibly be invented had already been. Marletto faces a similar attitude in her field. The book is her refutation of that stance, but it is not a negative one. Instead, she has the answer. She wants to expand the scope of physics laws and principles, by allowing the consideration of the kinds of things that could possibly be as well those that could not possibly be. She calls them counterfactuals, and there is simply no room in dynamical laws of physics for them. Today. Hers is a mind-expanding exercise of great importance. Great premise and great promise, that she pulls off beautifully.

These counterfactuals are given life in every chapter, from quantum theory to quantum computers, to information and knowledge, to work and heat, and all the major laws that apply to them. It can be a challenge to follow, so there is always a diverting short story between the chapters, a kind of amuse-bouche, or in this case, and amuse-cerveau to reset and reboot before the next intellectual leap of faith.

I think I can explain her frustration this way: The universe is a big, messy thing, but physics is all about elegant, compact and streamlined, universal laws. These contradictions and constraints can be lessened if physics were to admit counterfactual principles to the mix. It could lead to a far better understanding of the whole universe.

She explains that like everything else, physics is constantly changing, or should be. The iron-clad laws of the 1700s, like gravity, have proven to be incorrect or at very least insufficient, and new laws have replaced them. That the Earth was flat and the center of the universe was settled science for centuries, until those laws were replaced. The current state of the art, quantum theory and relativity, are incompatible, and one or both of them have to go. Soon, she hopes. But the next level will require far more flexible thinking, and that’s where counterfactuals come in. They expand the possibilities by reframing things in terms of what is possible, not just what can be measured. Or that are impossible, measured or not.

Marletto has set herself a monumental task, one she has been working out with David Deutsch, who it came from. She has to explain everything from basic points, something which I suspect helped them in understanding what they were undertaking. The result is she must explain things like information and knowledge in terms of how they work in physics. It is not always easy, and certainly far from intuitive, but she actually makes it entertaining:

“Something can hold information only if its state could have been otherwise. A computer memory is useless if all the changes in its contents are predetermined in the factory. The user could store nothing in it. And the same holds if you replace ‘factory’ with the Big Bang.” For example.

Knowledge, she says, is resilient information. It is transferable, copiable, and flippable. For her, knowledge is the most resilient stuff that can exist in our universe. The two known processes of creating knowledge are by conjecture and criticism in the mind, and by variation and natural selection in the wild.

For Marletto, physics laws are no-design laws. The randomness of evolution and natural selection rule the universe, and there is no overall scheme behind them. They do not revert to the mean so much as keep changing. Only elementary particles are unchanging. So physicists focus on them, the building blocks of everything else. But the deeper physics looks at them, the more it appears inadequate to describe and compartmentalize them. Reductionism is a curse in physics as much as it is (probably better known) in medicine.

But because of scientists’ insistence on measuring everything and putting it away forever, they have instead discovered that some elemental particles don’t want to be measured, or refuse to be measured, or can’t be measured if their location is known. Physics is waking up to the fact that sleek universal laws are neither. And it seems to be stuck there, awaiting release.

Readers will have to cut her some slack, too. Her examples can stretch credulity. In her discussion of knowledge, she conjures the existence of a hard drive that is full and that cannot be erased (we used to call these ROMs, read-only memory chips, and we used to joke about WOMs, write-only chips that could accept changes but could never be read. Government systems seemed to run on these. But I digress.) These vehicles cannot be carriers of information, because they cannot be copied or flipped, she says. But in practically the next breath, she cites vinyl discs (LPs) as sources of information. Spot the difference? Neither could I. But if you want to understand information and knowledge as they factor in theoretical physics, you have to go along.

The book is as wide-ranging as any good philosophy text. It touches on free will vs. determinism, ancient Greek myths, Aristotle teaching Alexander, and a grumpy old Italian woman fixing a game so Marletto would have to help on the farm. This is not the daily-bread physics 101 text that made you hate physics. And she has a story about that, too.

Marletto saves the big guns for the end, where she reframes the second law of thermodynamics in terms of counterfactuals. She takes 30 pages to do it, bashing it from every conceivable angle so that counterfactuals become the obvious saviors to a system crippled by its self-regulation and restrictions, patching over inconsistencies and the inexplicables. She says counterfactuals do a far better job describing it and making it work. I leave it to theoretical physicists to agree or disagree. But she makes the sale for me. Marletto is a great new voice

David Wineberg… (plus d'informations)