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 langua 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 voiceDavid Wineberg 。。。more