Ebook The Causal Universe mobi,epub

as investigated by other physical theories. We start with quantum mechanics, general relativity and astrophysics, and then go to more exotic research areas: physical theories based on noncommutative geometry and the multiverse idea. Very interesting, and well experimentally documented, things related to causality happen in quantum mechanics. Any discussion of causality would remain incomplete without even a brief presentation of the problems of causal relations and causal explanations specific to quantum mechanics. This task has been taken up by Marek Kuś (The Uncertain Future and the Ambiguous Past in Classical, Quantum and General Non-signaling Settings). With only a slight exaggeration, one can say that physics is the art of determining correlations between various parts of the physical world. Kuś gives a short but very lucid presentation of some aspects of this topic exhibited by recent developments in the theory of quantum correlations. Local theories, admitting only local correlations put some limits on possible correlations among results of measurements called Bell inequalities. Their violation, confirmed experimentally, testifies to the nonlocal character of the quantum world, and should be regarded as proof of the nondeterministic nature of quantum mechanical reality and its intrinsic, ontological randomness. In the classical setting, uncertainty about future events had an epistemological character - an event is random for us due to our lack of knowledge about all of its causes, whereas in quantum physics the future seems ontologically undetermined. The issue of causality and the emergence of structures is strictly linked with the problem of reductionism. If its strong version is true, we should exclude top-down causality and reduce complex structures to their simplest elements. The problem, as it appears in general relativity, is considered by Julian Barbour (Reductionist Doubts). He notices that if general relativity implements Machs principle, reductionism is challenged. Machs principle asserts that parts of the universe and their interactions do not determine the whole; on the contrary, the whole determines the way the parts behave. Whether general relativity implements Machs principle has been a matter of controversy every since Einstein created his theory of gravitation. Barbour has given what he believes is the correct definition of Machs principle and proposes an alternative interpretation of general relativity in which this theory appears much more holistic than in the usual interpretation. The Machian interpretation of general relativity radically changes the way we conceive of the parts and not just the way they interact. At the end, Barbour discusses the possible implications of a holistic quantum view of the universe. In the last hundred years, many branches of astrophysics have contributed to the advancement of cosmology. For instance, the hot beginnings of the Universe were confirmed observationally in the 1960s with the discovery of cosmic microwave background (CMB) radiation. Investigation of CMB, in turn, has allowed us to develop the Big Bang theory further. The X-ray background (XRB) constitutes another section of quasi-isotropic radiation flux reaching the Earth. The X-ray window was opened for astrophysics 50 years ago. The goal of Andrzej M. Sołtans paper (X-ray Background and Cosmology) is to inform us how this window has contributed to our understanding of the universe. One of the revolutionary turns which changed our perception of galaxies as the basic building blocks in the Universe, was due to X-ray observations of quasars and Seyfert galaxies and the activity of their nuclei. These two classes of extragalactic objects were known of earlier, but neither optical nor radio data provided an inkling that supermassive black holes are responsible for virtually all kinds of the nuclear activity of galaxies. Clusters of galaxies were the first extragalactic objects which were clearly recognized as X-ray sources. The detection of X-ray emissions from clusters bolstered the idea of dark non-baryonic matter as a dominating component of the matter density of the Universe. X-ray observations of hot intracluster gas allowed for the quantitative investigation of a gravitational field within clusters and the common acceptance of the reality of dark matter. Until recently, the question of dark matter was accompanied by similar one of dark baryons. This term was used to label a discrepancy between the density estimates of the baryonic matter in the early Universe and the present-day observations in the local Universe. X-ray observations have also alleviated this problem. It was possible because in soft X-rays, below 1 keV, a fraction of missing baryons are not completely dark. With the chapter by Andrzej Sitarz (Causality and Noncommutativity) we turn from the world of quasars and black holes to the most fundamental level of physics. In contemporary physics reigns a certain schizo