Questions and Answers What Is Physics?Throughout this book we shall be concerned greatly with questions and answers.The subject that an observer asks a question of will be denoted by a bold symbol such as Ψ.On the other hand, the question that is asked of a subject will be denoted by a barred bold symbol such as Q.Then the answer A that is obtained when that question is asked of that subject will be denoted by A ≡ QΨ.This notation will be used to explain what quantized detector networks (QDN) is all about and in its mathematical implementation.Note that the left-right ordering here is significant: ΨQ will mean something very different.If I, the author, were asked the question Q ≡ What is physics?, my answer QI would be QI = Physics is the process whereby observers first formulate, then ask, and then answer, empirical questions.We need to clarify some points about this answer.By empirical, we mean according to the established principles of science, whereby theorists make propositions or assertions and then establish the truth values of those propositions relative to experiments carried out by unbiased experimentalists.This is done to acquire information about systems under observation (SUOs) in order to add to our knowledge about the relative physical Universe (that part of the Universe empirically accessible to us).We are motivated to do all this for numerous reasons, not the least of which is basic curiosity.This is the view of physics taken in this book.Physics is emphatically not a discipline that philosophers and metaphysicists can meaningfully contribute to, because without empirical testing, any proposition has to be regarded as scientifically vacuous (empirically meaningless).The questions relevant to physicists are posed through experiments and consequently will be referred to as empirical questions.Other sorts of questions will be referred to as theoretical questions.
Questions and Answers What Is Physics?Throughout this book we shall be concerned greatly with questions and answers.The subject that an observer asks a question of will be denoted by a bold symbol such as Ψ.On the other hand, the question that is asked of a subject will be denoted by a barred bold symbol such as Q.Then the answer A that is obtained when that question is asked of that subject will be denoted by A ≡ QΨ.This notation will be used to explain what quantized detector networks (QDN) is all about and in its mathematical implementation.Note that the left-right ordering here is significant: ΨQ will mean something very different.If I, the author, were asked the question Q ≡ What is physics?, my answer QI would be QI = Physics is the process whereby observers first formulate, then ask, and then answer, empirical questions.We need to clarify some points about this answer.By empirical, we mean according to the established principles of science, whereby theorists make propositions or assertions and then establish the truth values of those propositions relative to experiments carried out by unbiased experimentalists.This is done to acquire information about systems under observation (SUOs) in order to add to our knowledge about the relative physical Universe (that part of the Universe empirically accessible to us).We are motivated to do all this for numerous reasons, not the least of which is basic curiosity.This is the view of physics taken in this book.Physics is emphatically not a discipline that philosophers and metaphysicists can meaningfully contribute to, because without empirical testing, any proposition has to be regarded as scientifically vacuous (empirically meaningless).The questions relevant to physicists are posed through experiments and consequently will be referred to as empirical questions.Other sorts of questions will be referred to as theoretical questions.
ConclusionsIn the Preface to this book, we started with Alice and Bob having very different views of their observations.Alice used an optical telescope and reported nothing unusual about a distant galaxy that she could see.Bob, on the other hand, detected intense radio activity in that galaxy.Our question was: who has the true view of that galaxy?We advised the reader that the answer is not Alice.Neither is it Bob.The answer is not both of them, nor is it neither of them.It is not a trick question either.So what is the answer that this book would supply?Our answer will come presently.While this book has set forth a definite mathematical perspective on empirical physics, it has contained quite a lot of commentary that might be disparaged as metaphysics or philosophy.Such commentary is generally frowned on in science, because it has no empirical content.It is vacuous.In our defense, we point out the obvious: science is not a robotic activity; it is carried out by humans and these are driven by their metaphysical, philosophical, and emotional imperatives.For instance, the hard-core scientific view that quantum theory needs no interpretation but only application is itself a philosophy.It is no more than a conditioned response, based on opinion and subscription to current scientific norms.It is, indeed, a philosophy of how to do quantum mechanics.So we all do it, in one way or another.Our concern in this book is that the way that we do it should be based soundly on scientific principles.The quantized detector approach that we describe and use in this book is our attempt to do just that.There is an excellent paper on all of this that has the provocative title "Quantum Theory Needs No Interpretation," by Fuchs and Peres (2000).It seems on the face of it to dismiss any sort of "interpretation" of quantum mechanics.In fact, close reading of it confirms (to us at least) the agenda that we have set out in this book.Yes, quantum mechanics needs no interpretation, when it is being applied to processes that take place in the information void.
In the Preface to this book, we started with Alice and Bob having very different views of their observations. Alice used an optical telescope and reported nothing unusual about a distant galaxy that she could see. Bob, on the other hand, detected intense radio activity in that galaxy. Our question was: who has the true view of that galaxy? We advised the reader that the answer is not Alice . Neither is it Bob . The answer is not both of them , nor is it neither of them . It is not a trick question either. So what is the answer that this book would supply? Our answer will come presently. While this book has set forth a definite mathematical perspective on empirical physics, it has contained quite a lot of commentary that might be disparaged as metaphysics or philosophy. Such commentary is generally frowned on in science, because it has no empirical content. It is vacuous. In our defense, we point out the obvious: science is not a robotic activity; it is carried out by humans and these are driven by their metaphysical, philosophical, and emotional imperatives. For instance, the hard-core scientific view that quantum theory needs no interpretation but only application is itself a philosophy. It is no more than a conditioned response, based on opinion and subscription to current scientific norms. It is, indeed, a philosophy of how to do quantum mechanics. So we all do it, in one way or another. Our concern in this book is that the way that we do it should be based soundly on scientific principles. The quantized detector approach that we describe and use in this book is our attempt to do just that. There is an excellent paper on all of this that has the provocative title “Quantum Theory Needs No Interpretation,” by Fuchs and Peres (2000). It seems on the face of it to dismiss any sort of “interpretation” of quantum mechanics. In fact, close reading of it confirms (to us at least) the agenda that we have set out in this book. Yes, quantum mechanics needs no interpretation, when it is being applied to processes that take place in the information void .
What is time? This book explores the hypothesis that time is discrete rather than continuous. Time is an enigma, so we should expect some metaphysics and philosophy to creep into the discussion. Our inclination is to avoid those disciplines as much as possible, so let us deal with them right now. Metaphysics and philosophy deal with statements and conjectures that cannot be empirically validated. In those disciplines there are constant references to absolutes such as existence, good and bad, and suchlike without further qualification, as if everyone accepted them as meaningful concepts. Absolutes are the key things we wish to avoid. For the record, we define an absolute statement as one that is considered to be true regardless of any caveats or criteria, i.e., context-free. In contrast, a contextual statement has a truth value that is meaningful only relative to its particular context. The idea that physical truth can be contextual is an unfamiliar and uncomfortable one to physicists conditioned to believe that the laws of physics transcend the context of observation because they can be empirically validated. In fact, that is a circular line of reasoning. Every experiment is defined by its own context and experimentalists have to work hard to create that context: the search for the Higgs particle at the Large Hadron Collider did not happen overnight.
Scientists have been debating the meaning of quantum mechanics for more than a century. This book for graduate students and researchers gets to the root of the problem: how the contextual nature of empirical truth and the laws of observation impact on our understanding of quantum physics. Bridging the gap between non-relativistic quantum mechanics and quantum field theory, this novel approach to quantum mechanics extends the standard formalism to cover the observer and their apparatus. The author demystifies some of the aspects of quantum mechanics that have traditionally been regarded as extraordinary, such as wave-particle duality and quantum superposition, emphasizing the scientific principles rather than the mathematical modelling. Including key experiments and worked examples throughout, the author encourages the reader to focus on empirically sound concepts and avoid metaphysical speculation. Originally released in 2017, this title has been reissued as an Open Access publication on Cambridge Core.
Mathematicians really understand what mathematics is. Theoretical physicists really understand what physics is. No matter how fruitful the interplay between the two subjects, the deep intersection of these two understandings seems to me to be quite modest. Of course, many theoretical physicists know a lot of mathematics. And many mathematicians know a fair amount of theoretical physics. This is very different from a deep understanding of the other subject. There is great advantage in the prospect of each camp increasing its appreciation of the other's goals, desires, methodology, and profound insights. I do not know how to really go about this in either case. However, the book in hand is a good first step for the mathematicians. The method of the text is to explain the meaning of a large number of ideas in theoretical physics via the splendid medium of mathematical communication. This means that there are descriptions of objects in terms of the precise definitions of mathematics. There are clearly defined statements about these objects, expressed as mathematical theorems. Finally, there are logical step-by-step proofs of these statements based on earlier results or precise references. The mathematically sympathetic reader at the graduate level can study this work with pleasure and come away with comprehensible information about many concepts from theoretical physics … quantization, particle, path integral … After closing the book, one has not arrived at the kind of understanding of physics referred to above; but then, maybe, armed with the information provided so elegantly by the authors, the process of infusion, assimilation, and deeper insight based on further rumination and study can begin.
Why does observing a particle change an experiment? What gives matter its mass? How do clocks respond to motion and gravity? And what can we really know about the beginning of the universe? Modern Physics Through Questions explores these puzzles through experiments, diagrams and simple arithmetic before introducing compact mathematical notation. Its four parts cover quantum physics, particles and interactions, spacetime and gravity, and cosmology. Each chapter explains the physical setting before asking its questions. Prediction prompts and 87 worked exercises invite readers to test their reasoning; optional mathematical chapters provide a route into more formal treatments. Written for able graduates, undergraduates, researchers entering a new field and curious readers, the book distinguishes established results, assumptions used in examples and questions that remain unsettled. Includes 30 diagrams, a glossary and guided further reading. This combined edition brings together the four source books into a single 182-page print layout, with 87 questions and worked exercises, 30 diagrams, a 40-term glossary and 33 references. The text is the combined edition also published on Kindle. Print navigation, pagination and monochrome artwork have been adapted for paperback. Paperback ISBN: 9798163906604 (Amazon KDP-assigned ISBN; imprint: Independently published). This Zenodo deposit is the digital companion PDF and is linked to the paperback as an alternative format. The four source volumes remain available at their existing DOIs. OpenAI's Codex assisted with organisation, prose, diagrams and teaching checks. Responsibility for the content rests with the author.