[...]... and correspondingly ur theory) If the ur hypothesis is correct, the symmetry of urs must play a distinguished role in physics At this point the second pillar of the ur theoretic structure comes in: the quantum theory of alternatives, ur theory, is the theory of three-dimensional space Mathematically, Weizs¨cker had come across the known fact that SU (2), a the basic symmetry group of urs, is locally isomorphic... early a The Structure of Physics is therefore in many respects still an important book: as an eyewitness to the physics of the twentieth century, due to his personal acquaintance with physicists like Heisenberg and Bohr, Weizs¨cker’s a observations, especially in the third part of the book, are of extraordinary value for the history of science The physical core of the book, the presentation of ur theory... here, and of the entire subsequent reconstruction of physics, was an analysis of Boltzmann’s derivation of the second law of thermodynamics by means of statistical mechanics (Chap 7) The derivation is consistent only if the concept of probability is applied there exclusively to future events As a consistency check one can then show afterwards that the facticity of the past and the openness of the future... overview It remains for the reader either to read it immediately as an introduction to the entire book, to use it as a “road map” while perusing the book, or treat it as a review at the end 1.2.1 Methodology The theme of this book is the unity of nature as manifested to us by the unity of physics The historical form of the unity of physics (Chap 2) is a sequence or system of closed theories Following Heisenberg... Heisenberg at the head of the book Einstein was the genius of the century The theory of relativity is his work, and it was on his account that quantum theory got under way All younger workers remain under the spell cast by his insights Bohr was the inquiring master of atomic theory He pressed onward into realms from which Einstein shut himself off; the completion of quantum theory was the handiwork of his... is the fact that both themes play a central role in present-day fundamental physics The first assumption, before the background of quantum theory, is nothing but an anticipation of the concept of qubits of present quantum information theory Nevertheless, Weizs¨cker a goes in a decisive manner beyond the usual (quantum) information theory: he wants to consider the “abstract structure of quantum theory... lessons learned from the facts of the past to the open questions of the future The use of time as parametertime—i.e., within the concept “spacetime”—is therefore to be distinguished from the asymmetric directedness of time This basically corresponds to McTaggart’s distinction between B- and A-series of time.16 The two essential a priori assumptions of Weizs¨cker’s philosophy of physics may therefore be a... Introduction 1.1 The question Sapere aude What is the truth of physics? Physics is based on experience Theories formulate laws that apply to experience The system of physical theories developed over the past few centuries is converging to a unified, comprehensive theory Quantum theory is presently the closest approximation to such a general theory of physics known This theory appears to be valid for all of nature,... is well known that the set of subspaces of a Hilbert space form a nondistributive lattice, generally referred to as quantum logic If one interprets quantum theory abstractly as the (meta-)theory of empirical theories, as Weizs¨cker does, then the most general form of an ema pirical theory of predictions can be expressed in quantum logic—specifically, the structure of the lattice of empirically verifiable... by the school of Ashtekar Ashtekar recognized that spin variables permit important progress in the canonical quantization of gravity.26 The transition to the loop representation of Rovelli and Smolin, and the geometric interpretation of models of canonical quantum gravity, underscore the significance of spinorism for these programs.27 In contrast to the “heavy machinery” of string theories, all of the . h0" alt="" The Structure of Physics Fundamental Theories of Physics An International Book Series on The Fundamental Theories of Physics: Their Clarification,. 234 viii Contents Part III On the interpretation of physics 9 The problem of the interpretation of quantum theory 243 9.1 About the history of the interpretation