Physics and Philosophy: The Revolution in Modern Science

Loved this book that exposits physics and philosophy (what used to be called natural science), from one of the leading theoretical physicists of the last century. We may have made a mistake in our materialistic view of the world, our apparent sense of rationality driven by subject-object boundaries that have taken place in the last 4 centuries since Newton. This has been a subject of intense interest to me last few years and this book was like having a conversation with a friend with similar interests. There are no pretensions, no hiding behind abstractions - just simple, plain speak from the scientist who formulated the uncertainty principle. My notes - • Strange ideas in relativity - time dilation and length contraction, curved spaces and black holes. There is no absolute universal time and no concept of simultaneity in the universe • The deepest philosophical problem with theory of relativity is the possibility that the universe came into existence at a finite moment in the past and with it were born not just matter and energy but also space and time (Time may not stretch back to all eternity) • Its easy to see what the theory predicts (quantum mechanics) but hard to understand what it “means” • Heisenberg’s uncertainty principle - all physical quantities observed are subject to unpredictable fluctuations, their values are not precisely defined. Uncertainty in position x Uncertainty in momentum = Planck’s constant (So there’s a trade-off in precision when measuring one over the other). The particle simply does not posses simultaneously precise values of position and momentum (with respect to us, the observers - akin to ‘if a tree falls in a forest…’ problem) • Uncertainty in physical processes (markets/thermodynamics) is due to missing information rather than a fundamental limitation as in quantum particles • The popular model of atom with electrons circling the nucleus is badly misleading as its impossible to know precise trajectory of electron from point A to point B • Two quantum systems initially identical may go on and do different things (all else remaining equal) - its still not complete anarchy as these different things can be defined by probabilities • quantum mechanics is a statistical theory - definite predictions about ensembles but not of individual systems • weather prediction is also statistical mechanics - but chance element is “inherent” in quantum systems, rather than our limited grasp of information of variables • Einstein hoped that beneath the quantum chaos might lie a familiar deterministic dynamic (hence “god does not play dice”). Heisenberg and Bohr strongly opposed Einstein on this • EPR paradox - A system of two particles that interact and fly apart that carry information of the other - by measuring one particle, it would be then possible to know either position of momentum of the other - speed of light prohibits such measurement as information cannot carry faster than “c”- heart of the conflict between Einstein’s classical worldview (dogmatic realism) and Heisenberg and Bohr’s uncertain one • In classical world, our observations do not “create” reality - merely “uncovers” reality. According to Copenhagen interpretation of quantum mechanics, there’s no objective reality in the quantum world - nothing is well-defined. It is our observations that create the reality we perceive (An electron is not a “thing”, as a billiard ball may be) • Bohr’s principle of complementarity - same system can display apparently contradictory properties - like electron behaving as both a wave and a particle - this ambiguity is not contradictory but is complementary faces of a single reality - its up to the experimenter to expose the aspect he so chooses to (position vs momentum, wave vs particle) - so observation/experiment is a crucial part of the observation - the transition from the possible to the actual happens in the act of observation • Our language is limited by our real-world and limits our imagination. any attempt to explain what really happens in the quantum world is thus limited by our limits of imagination based on the real-world we observe (hence intuition doesn’t work!) • Blackbody radiation, photoelectric effect, electromagnetic waves - were some of the earliest precursors that led to definition of quantum theory • Asking the right question is frequently more than halfway to the solution of the problem (well stated is half solved) • Quantum properties arise due to our deficiency in knowledge of the electron, than as an inherent property of the electron (same as in weather systems - epistemology vs ontology) • Thales of Miletus in 6th Century BC thought Water was the fundamental material. Anaximander, pupil of Thales denied it could be water or any known substance. He taught the primary substance was infinite, eternal and ageless - Being and Becoming - the primary substance infinite and ageless was “Being” and it degenerates into various forms (“Becoming”) leading to endless struggles and returns back into that which is shapeless and characterless (Sort of Hindu philosophy, sort of pre-empted big bang) • Throughout history we have had an obsession to find the fundamental particle - we thought it was water (Thales), then air (Anaximenes), then fire (Heraclitus), pluralism from monism (earth, water, air and fire) of Empedocles, an infinitely small seed from which everything was made of (Anaxigoras) - sort of precursor to atom, and so on • Modern physics is closer to Heraclitus - replace “fire” with “energy” - that which makes all elementary particles, that which moves - causes all change in the world • Plato - prisoners in a cave thought experiment - men bound in a cave looking in only one direction with fire behind them see objects behind them and themselves only as shadows on the wall • Descartes - in “Discourse on method” - not believing senses, driven by doubt and thus thought - the famous “cogito ergo sum” - he thus made the triangle of “God-World-I” - separating and elevating God from the world - here on philosophy and natural science separated ‘res cogitans’ and ‘res extensa’ - me and my world - subject and object - cartesian division between self and the world - the world was then described by physics and chemistry and same applied to the mind led to concept of “free will” and that one can speak about the world without speaking about God or ourselves (God here in my opinion is nothing but probability) - we need to get back to “practical realism” of natural science from the “dogmatic realism” of modern physics concerning the material world. • Locke, Berkeley, Hume - empiristic philosophy - All knowledge is ultimately founded in experience (Locke). If all knowledge is founded in experience, there’s no meaning to the statement that things really exist (Berkeley). Hume denied induction and causation which when taken seriously would destroy the basis of all empirical science • If we attach symbols to phenomena, the symbols can then be combined by certain rules (as in math) and statements about the phenomena can be represented as combinations of symbols. Now, a combination of symbols that doesn’t comply with rules is not wrong but conveys no meaning (like complex numbers) • Kant - ‘Critique of pure reason’ - Our knowledge is in part ‘a priori’ and not inferred inductivity from experience - he also distinguished analytic (what follows from logic) and synthetic propositions (empirical knowledge) • It will never be possible by pure reason to arrive at some absolute truth • Space and time belonged both to newtonian mechanics and theory of relativity - in the former they were independent and in the latter, they were connected by Lorentz transofmration • Newtonian mechanics, theory of heat, electricity and magnetism, quantum theory - all arose as closed system of concepts with their own axioms - there may arise a 5th set in the future with theory of elementary particles • While chemistry can be understood as a limiting case of physics, biology and living organisms display a degree of stability that cannot be explained by physical and chemical laws alone - its the stability of process or function, rather than stability of form (as in atoms/crystals) • Some scientists were inclined to think psychology could be explained by physical and chemical phenomena - from quantum-theoretical standpoint, there’s no reason for such an assumption. Quantum theory does not allow a completely objective description of nature. • Every energy carries some mass with it but it is miniscule and that’s why it was not observed before *(E = mc^2 for intuition). The binding energy of particles in the nucleus of an atom is what shows up in their masses (and in the atomic bomb) • The concepts of space and time belong to our relation to nature, not to nature itself (Kant) • Every act of observation is by its very nature, an irreversible process • Matter in itself is not a reality but only a possibility (potentia) - Aristotle. The statue is potentially in the marble, before it is cut out by the sculptor • Our natural language and concepts of classical physics can only apply to phenomena for which velocity of light can be considered infinite - a mathematical language is necessary for everything else in the universe. With expansion of scientific knowledge, our language also expands and with it the word’s applicability in a wider sense (Eg. energy, electricity, entropy are widely used in different contexts in natural language) • Most fruitful developments frequently take place when two different lines of thought meet It is always lovely when a scientist tries to unify disparate modes of thought, history, philosophy and is so open to ideas from different disciplines. This is like reading the diary of such a great scientist and if the topic of uncertainty/probability, subject-object boundaries, what makes up the fabric of reality and who we are, interests you, then this book is a must read. 11/10

Excellent book. All science students should read

Reality

I think every engineer, every student of science could benefit from the wisdom this book has to offer. The author goes back and forth between the development of quantum theory and its causal connection to the history of (mostly western) scientific thought process. For its size, it touches on many topics concerning not just science & technique but also its relationship with the 'human condition'. For someone studying quantum theory on their own, I would recommend this book as a well motivating precursor to more technical books.

Heisenberg explained the philosophical development in history that gradually gave rise to the scientific world view today we have. being neutral, he presented all the different perspectives of big figures of history and showed how they were similar or way form each other. the language he used was very technical which added to its good flavour. i really enjoyed reading it.

Variety of subjects

Beautiful book from one of the great minds of the twentieth century.

Packaging and the book quality is really really bad. This is the worst book quality I've ever seen. Looks like it was printed from used recycled low quality paper and very bad binding. BUT GREAT BOOK CONTENT! Legendary and renowned scientist Werner Heisenberg. One of kind mind. Rare even among the top scientists.

Preso come regalo di Natale per mio genero, ingegnere cervellone che quando lo ha visto ne è rimasto entusiasta. Contento lui….

Some of the most interesting books about physics are not the ones filled with equations, but the ones written by the scientists who stepped back and asked what those discoveries actually mean. I bought this copy of Physics and Philosophy: The Revolution in Modern Science by Werner Heisenberg in 2000 as part of a long-term personal reading project exploring the thinkers who reshaped modern scientific thought. Few scientists were better placed to write such a reflection. Heisenberg was not only one of the principal architects of quantum mechanics, he was also deeply aware that the scientific revolution of the twentieth century forced a reconsideration of many philosophical assumptions that had guided science since the time of Newton. What makes this book particularly valuable is that it explains those conceptual shifts in clear and accessible language. Rather than presenting physics purely as technical theory, Heisenberg explores the deeper implications of modern science: the role of the observer, the limits of determinism, and the surprising ways in which measurement itself influences what we know about the physical world. Reading the book today is striking. Many of the questions raised by quantum physics — about uncertainty, observation, and the nature of knowledge — remain central to contemporary discussions about science and technology. Readers interested in the philosophy of science, the intellectual history of modern physics, or the deeper conceptual foundations of scientific discovery will find this book especially rewarding. It is one of those rare works written by a scientist who fully understood the philosophical significance of the discoveries he helped create. I purchased this copy myself and continue to revisit it as part of a long-term reading archive documenting the thinkers who shaped modern knowledge.

Heisenburg a total genuis and started an important branch of physics quantum physics explains the old and new philosophical limitations.

Complex book. Takes some time to gasp all the concepts and links with Philosophy. But once you start to assimilate, well you’re a changed man. I would recommend to read once, then a second time with a little notebook to jot down important concepts.

On my personal journey reading 'classical' books from the past I have recently read Heisenberg's 'Physics and Philosophy' , originally published 1958. More than 50 years later this seems to be still a very remarkable book, with an easy reading and a scope of thinking which is rare today. PHYSICS Heisenberg describes in his book the modern findings in physics in a language which does not presuppose any mathematics. And he describes these central findings in a way which is even clearer than written in the complex mathematical machinery of modern physics. The detection of the atomic structure of matter, the discrete structure of the energy levels, the velocity of light as the upper limit of the velocity of all moving bodies, the uncertainty in the description of the behavior of the atomic elements caused by the inevitable interaction between observer and observed object, the equivalence of matter and energy as well as the new structure of the physical space (non-euclidean) compared to the space of our perceptions, imaginations and the everyday space of daily actions. I can not remember any other book about physics which explains these developments in such a clearness and directness. PHILOSOPHY The book gains even more because Heisenberg compares the concepts of the modern physics with the main concepts of the old Greek philosophy as well as with philosophers like Descartes, Locke, Hume, Berkeley, and Kant. It is interesting to see that human kind was more than 2000 years ago capable to develop conceptual models of matter and nature which logically come very close to the modern concepts of the atom and its parts. At the same time it is interesting to see, that despite of this astonishing conceptual thinking the lack of proper measurement instruments and the lack of a sufficient mathematical language didn't allow better theories. Thus the development of new measurement instruments, new strong languages like modern mathematics as well as the right experiments appear to play a fundamental role in the construction of better world models; they are not 'outside' of the story but a central moment of it. LANGUAGE Heisenberg describes in length the insufficiency of language to describe the new findings in physics, especially those headed under the label of quantum mechanics, not an insufficiency only of the everyday language, but also an insufficiency of the mathematical language as such. While the concrete experiments are described with everyday language expressions and the terms of classical physics do the mathematical expressions describe formal structures like probability fields which encode expectations about the behavior of the quanta which as such are not concrete objects. From the point of theory there is no complete consistent solution conceivable for this problem, only 'practically' by relating concrete experimental data with the abstract mathematical models. WELTBILD/ WORLD VIEW Heisenberg describes not only the development of modern physics but considers also the effect of this new world picture on the overall world view of mankind. He suggests that the physical world view before quantum theory was too narrow, not giving satisfying answers to central phenomena like biological life, the human mind or even the concept of human soul. Only quantum theory has -according to Heisenberg-- forced an opening of central concepts, has widened the concept of objectivity, has reinforced the awareness that the observer is a central moment of the observed object; there is no 'real objectivity'. Knowledge is always a construct under certain conditions where we have to 'extrapolate' the 'hidden' structures with some probability. With regard to biology he states explicitly "...we are obviously still very far from such a coherent and closed set of concepts for he description of biological phenomena. The degree of complication in biology is so discouraging that one can at present not imagine any set of concepts in which the connections could be so sharply defined that a mathematical representation could become possible". (PP79f)" If we go beyond biology and include psychology in the discussion then there can scarcely be any doubt but that the concepts of physics, chemistry, and evolution together will not be sufficient to describe the facts ..".(PP80) CRITICAL REMARKS If one wants to find weak points in the wonderful book, one can mention some. There is nearly no citation; this makes it difficult to follow the sources (if one wants). The look to philosophy is very narrow; many modern developments have not been cited, especially not the large amount of work in semiotics, philosophy of language, and formal logic. He mentions the limits of mathematical theories without citing the famous results of Goedel (1931) and Turing (1936/7). Or, he mentions the logic of quanta proposed by Weizsäcker which has the format of a type logic; this has been introduced by Whitehead-Russel already in 19010ff. Heisenberg argues for the limits of physics with regard to biology using arguments which resemble those of Schroedinger in his famous book of 1944, without mentioning Schrödinger. Despite all this, for me this is a very remarkable book, extremely clear, and very inspiring. FUTURE The book shows that central questions regarding man are not solved. The phenomenon of life is still the big challenge of science.