Vesselin Petkov - Böcker

All physicists would agree that one of the most fundamental problems of the 21st century physics is the dimensionality of the world. In the four-dimensional world of Minkowski (or Minkowski spacetime) the most challenging problem is the nature of the temporal dimension. In Minkowski spacetime it is merely one of the four dimensions, which means that it is entirely given like the other three spacial dimensions. If the temporal dimension were not given in its entirety and only one constantly changing moment of it existed, Minkowski spacetime would be reduced to the ordinary three-dimensional space.But if the physical world, represented by Minkowski spacetime, is indeed four-dimensional with time being the fourth dimension, then such a world is drastically different from its image based on our perceptions. Minkowski four-dimensional world is a block Universe, a frozen world in which nothing happens since all moments of time are given ‘at once', which means that physical bodies are four-dimensional worldtubes containing the whole histories in time of the three-dimensional bodies of our everyday experience. The implications of a real Minkowski world for physics itself and especially for our world view are enormous.The main focus of this volume is the question: is spacetime nothing more than a mathematical space (which describes the evolution in time of the ordinary three-dimensional world) or is it a mathematical model of a real four-dimensional world with time entirely given as the fourth dimension? It contains fourteen invited papers which either directly address the main question of the nature of spacetime or explore issues related to it.

The book presents seven fundamental concepts in spacetime physics mostly by following Hermann Minkowski’s revolutionary ideas summarized in his 1908 lecture "Space and Time."

This expanded second edition of Relativity and the Nature of Spacetime c- tains several major changes and a number of additions to different ch- ters. Two chapters (Chaps. 6 and 7), which discussed two speci?c groups of arguments against the reality of spacetime, have been transformed into - pendices (A and B). Two new chapters (Chaps. 6 and 10) have been added. Chapter 6, entitled Why Is the Issue of the Nature of Spacetime So Imp- tant?, elaborates on what was Sect. 5. 6 of the ?rst edition, and addresses some recent work on the nature of spacetime – for example, the growing (or evolving) block universe model of the world, which has recently been - vived by several physicists as what appears to be the last remaining alter- tive to the Minkowski absolute four-dimensional world (after it had become an undeniable fact that three-dimensionalism, or presentism, contradicts the relativistic experimental evidence). Chapter 10, entitled Spacetime and the Nature of Quantum Objects and based on what used to be Sects. 6. 2 and 6. 3 in the ?rst edition, explores the implications of the issue of the nature of spacetime for quantum physics, in order to see whether it can provide some insight into the nature of quantum objects. Two new sections have been included, namely, Sect. 5. 6 entitled Re- tivization of Existence and Observers in General Relativity and Sect. 7. 6 - titled Probing the Anisotropic Velocity of Light by a Terrestrial Experiment.

In 1908 Hermann Minkowski gave the four-dimensional(spacetime) formulationof special relativity[1]. In fact,HenriPoincare[ ' 2] rst noticedin1906that the Lorentz transformations had a geometric interpretation as rotations in a four-dimensional space with time as the fourth dimension. However it was Minkowski, who succe- fully decoded the profound message about the dimensionality of the world hidden in the relativity postulate, which re ects the experimental fact that natural laws are the same in all inertial reference frames. Unlike Poincare, ' Minkowski did not regardspacetime - the uni cation of space and time - as a convenientmathematical space, but insisted that this absolute four-dimensional world, as Minkowski called it, represents physical phenomena and the world more adequately than the relativity postulate: "the word relativity-postulate...seems to me very feeble. Since the pos- late comes to mean that only the four-dimensional world in space and time is given by the phenomena...I prefer to call it the postulate of the absolute world"[3].The impact of Minkowski's ideas on the twentieth century physics has been so immense that one cannot imagine modern physics without the notion of spacetime. It would hardly be an exaggeration to say that spacetime has been the greatest discoveryinphysicsofall times. Theonlyotherdiscoverythatcomesclosetospa- time is Einstein's general relativity, which revealed that gravity is a manifestation of the curvature of spacetime. But it was the discovery of spacetime, which paved the way for this deep understanding of what gravity really is. Einstein saw the link betweenthegeometryofspacetimeandgravitationonlyafterheovercamehis initial hostile attitude toward the notion of spacetime.

This expanded second edition of Relativity and the Nature of Spacetime c- tains several major changes and a number of additions to different ch- ters. Two chapters (Chaps. 6 and 7), which discussed two speci?c groups of arguments against the reality of spacetime, have been transformed into - pendices (A and B). Two new chapters (Chaps. 6 and 10) have been added. Chapter 6, entitled Why Is the Issue of the Nature of Spacetime So Imp- tant?, elaborates on what was Sect. 5. 6 of the ?rst edition, and addresses some recent work on the nature of spacetime – for example, the growing (or evolving) block universe model of the world, which has recently been - vived by several physicists as what appears to be the last remaining alter- tive to the Minkowski absolute four-dimensional world (after it had become an undeniable fact that three-dimensionalism, or presentism, contradicts the relativistic experimental evidence). Chapter 10, entitled Spacetime and the Nature of Quantum Objects and based on what used to be Sects. 6. 2 and 6. 3 in the ?rst edition, explores the implications of the issue of the nature of spacetime for quantum physics, in order to see whether it can provide some insight into the nature of quantum objects. Two new sections have been included, namely, Sect. 5. 6 entitled Re- tivization of Existence and Observers in General Relativity and Sect. 7. 6 - titled Probing the Anisotropic Velocity of Light by a Terrestrial Experiment.

In 1908 Hermann Minkowski gave the four-dimensional(spacetime) formulationof special relativity[1]. In fact,HenriPoincare[ ' 2] rst noticedin1906that the Lorentz transformations had a geometric interpretation as rotations in a four-dimensional space with time as the fourth dimension. However it was Minkowski, who succe- fully decoded the profound message about the dimensionality of the world hidden in the relativity postulate, which re ects the experimental fact that natural laws are the same in all inertial reference frames. Unlike Poincare, ' Minkowski did not regardspacetime - the uni cation of space and time - as a convenientmathematical space, but insisted that this absolute four-dimensional world, as Minkowski called it, represents physical phenomena and the world more adequately than the relativity postulate: "the word relativity-postulate...seems to me very feeble. Since the pos- late comes to mean that only the four-dimensional world in space and time is given by the phenomena...I prefer to call it the postulate of the absolute world"[3].The impact of Minkowski's ideas on the twentieth century physics has been so immense that one cannot imagine modern physics without the notion of spacetime. It would hardly be an exaggeration to say that spacetime has been the greatest discoveryinphysicsofall times. Theonlyotherdiscoverythatcomesclosetospa- time is Einstein's general relativity, which revealed that gravity is a manifestation of the curvature of spacetime. But it was the discovery of spacetime, which paved the way for this deep understanding of what gravity really is. Einstein saw the link betweenthegeometryofspacetimeandgravitationonlyafterheovercamehis initial hostile attitude toward the notion of spacetime.