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This book is unique and exceptional in dealing with the notion of physical time rigorously, both logically and empirically. The central theme is the intimate relation between physical time and cosmic gravity. It establishes and explains, in an accessible manner, the one crucial physical fact that has been missed in the development of modern physics—that the enormous gravity of the matter and energy in the Universe is the controller and cause of the relativistic time. The material in the book is accurate and free of the ambiguities in the discussion of time and its modifications (dilation), synchronization of clocks, and simultaneity. The contents go beyond the current theories of relativity that fail to incorporate the cosmic gravity in their structure. The discussion of clocks in satellite navigational systems (like the GPS) is the most complete and accurate. The book offers several new insights, and it is the only available treatise on the complete physical truth about time. The contents are addressed to a wide range of readers, from general readers and students to experienced researchers, and will also appeal well to philosophers and historians of physics. This book has the enabling quality to deal with difficult questions about physical time, with unprecedented clarity and without paradoxes.

This book shows how one can combine Yang-Mills gauge symmetry and effective Einstein-Grossmann metric tensors to tackle physical problems at microscopic, macroscopic and super-macroscopic length scales in inertial frames, including the late-time accelerated cosmic expansion due to baryon masses and charges. The combination of gauge symmetry and effective metric tensor provides a framework and leads to an alternative dynamics of cosmic expansion based on quantum Yang-Mills gravity at a super-macroscopic limit. Together with cosmological principle, one can investigate and derive expanding scale factors, the age of the universe, the cosmic redshift, and the Hubble recession velocity with an upper limit. All these discussions are based on inertial frames with operationally defined space and time coordinates.

A sweeping account of the century of experimentation that confirmed Einstein's general theory of relativity, bringing to life the science and scientists at the origins of relativity, the development of radio telescopes, the discovery of black holes and quasars, and the still unresolved place of gravity in quantum theory.Albert Einstein did nothing of note on May 29, 1919, yet that is when he became immortal. On that day, astronomer Arthur Eddington and his team observed a solar eclipse and found something extraordinary: gravity bends light, just as Einstein predicted. The finding confirmed the theory of general relativity, fundamentally changing our understanding of space and time.A century later, another group of astronomers is performing a similar experiment on a much larger scale. The Event Horizon Telescope, a globe-spanning array of radio dishes, is examining space surrounding Sagittarius A•, the supermassive black hole at the center of the Milky Way. As Ron Cowen recounts, the foremost goal of the experiment is to determine whether Einstein was right on the details. Gravity lies at the heart of what we don't know about quantum mechanics, but tantalizing possibilities for deeper insight are offered by black holes. By observing starlight wrapping around Sagittarius A•, the telescope will not only provide the first direct view of an event horizon—a black hole's point of no return—but will also enable scientists to test Einstein's theory under the most extreme conditions.Gravity's Century shows how we got from the pivotal observations of the 1919 eclipse to the Event Horizon Telescope, and what is at stake today. Breaking down the physics in clear and approachable language, Cowen makes vivid how the quest to understand gravity is really the quest to comprehend the universe.

This book presents an overview of the current understanding of gravitation, with a focus on the current efforts to test its theory, especially general relativity. It shows how the quest for a deeper theory, which would possibly incorporate gravity in the quantum realm, is more than ever an open field.The majority of the contributions deals with the manifold facets of “experimental gravitation”, but the book goes beyond this and covers a broad range of subjects from the foundations of gravitational theories to astrophysics and cosmology. The book is divided into three parts. The first part deals with foundations and Solar System tests. An introductory pedagogical chapter reviews first Newtonian gravitational theory, special relativity, the equivalence principle and the basics of general relativity. Then it focuses on approximation methods, mainly the post-Newtonian formalism and the relaxed Einstein equations, with a discussion on how they are used in treating experimental tests and in the problem of generation and detection of gravitational waves. Following this is a set of chapters describing the most recent experiments, techniques and observations on the testing of gravity theories in the laboratory, around the Earth and in the Solar System.The second part is dedicated to astrophysical topics deeply linked with the study of gravitation, namely binary pulsars and the perspective of direct detection of gravitational waves. These cases are paradigmatic in that the gravitational signals act at the same time as messengers helping us to understand the properties of important and wide classes of astrophysical objects. The third part explores the many open issues in current knowledge of gravitation machinery, especially related to astrophysical and cosmological problems and the way possible solutions to them impact the quest for a quantum theory of gravitation and unified theory. Included is a selection of the many possiblepaths, giving a hint to the subtleties one is called upon. Whenever possible, a close link to observational constraints and possible experimental tests is provided. In selecting the topics of the various contributions, particular care has been devoted to ensure their fit in a coherent representation of our understanding of gravitational phenomena. The book is aimed at graduate level students and will form a valuable reference for those working in the field.

This book gives a survey of astrophysics at the advanced undergraduate level, providing a physics-centred analysis of a broad range of astronomical systems. It originates from a two-semester course sequence at Rutgers University that is meant to appeal not only to astrophysics students but also more broadly to physics and engineering students. The organisation is driven more by physics than by astronomy; in other words, topics are first developed in physics and then applied to astronomical systems that can be investigated, rather than the other way around. The first half of the book focuses on gravity. The theme in this part of the book, as well as throughout astrophysics, is using motion to investigate mass. The goal of Chapters 2-11 is to develop a progressively richer understanding of gravity as it applies to objects ranging from planets and moons to galaxies and the universe as a whole. The second half uses other aspects of physics to address one of the bigquestions. While “Why are we here?” lies beyond the realm of physics, a closely related question is within our reach: “How did we get here?” The goal of Chapters 12-20 is to understand the physics behind the remarkable story of how the Universe, Earth and life were formed. This book assumes familiarity with vector calculus and introductory physics (mechanics, electromagnetism, gas physics and atomic physics); however, all of the physics topics are reviewed as they come up (and vital aspects of vector calculus are reviewed in the Appendix).

The book points out what has gone wrong with physics since Einstein's formulation of this theory of general relativity a century ago. It points out inconsistencies and fallacies in the standard model of the big bang and the inflationary scenario which was supposed to have overcome those shortcomings, the evolution of string theory from a theory of the strong interaction to a theory of gravitation and quantum mechanics which has not produced a single verifiable prediction, and what it has accomplished is reaffirming wrong results like the entropy of a black hole, which is not an entropy at all. There have even been attempts to demote gravity to an emergent phenomenon with catastrophic effects. We know exactly what happened at 10-34 seconds after the big bang, but do not know how fast gravity propagates, whether gravitational waves exist, and what are the limits of Newton's law. Attempts to rectify this are the prediction of dark energy/matter, which has never been observed nor ever will, and MOND. The latter is really not a modification of Newtonian mechanics, but a transformation of a dynamical law into a statistical one.

This book deals with the relationship between gravitation and elementary particle physics, and the implications of these subjects for astrophysics. There has, in recent years, been renewed interest in theories that connect up gravitation and particle physics, and in the astrophysical consequences of such theories. Some of these accounts involve a time-variation of the Newtonian gravitational parameter, G. In this respect, the present book may be regarded as a companion to my Cosmology and Geophysics (Hilger, Bristol, 1978). There is some overlap as regards the discussion of G-variability, but the emphasis in the present book is on astrophysics while the emphasis in the other one is on geophysics. The subject is a very broad one indeed, and in giving a review of it I have adopted a somewhat unorthodox way of presenting the material involved. The main reason for this is that a review of such a wide subject should aim at two levels: the level of the person who is interested in it, and the level of the person who is professionally engaged in research into it. To achieve such a two-level coverage, I have split the text up into two parts. The first part (Chapters 1-7) represents a relatively non-technical overview of the subject, while the second part (Chapters 8-11) represents a technical examination of the most important aspects of non-Einsteinian gravitational theory and its relation to astrophysics.

This book comprises expository articles on different aspects of gravitation and cosmology that are aimed at graduate students. The topics discussed are of contemporary interest assuming only an elementary introduction to gravitation and cosmology. The presentations are to a certain extent pedagogical in nature, and the material developed is not usually found in sufficient detail in recent textbooks in these areas.

“Newton's Gravity” conveys the power of simple mathematics to tell the fundamental truth about nature. Many people, for example, know the tides are caused by the pull of the Moon and to a lesser extent the Sun. But very few can explain exactly how and why that happens. Fewer still can calculate the actual pulls of the Moon and Sun on the oceans. This book shows in clear detail how to do this with simple tools. It uniquely crosses disciplines – history, astronomy, physics and mathematics – and takes pains to explain things frequently passed over or taken for granted in other books. Using a problem-based approach, “Newton's Gravity” explores the surprisingly basic mathematics behind gravity, the most fundamental force that governs the movements of satellites, planets, and the stars. Author Douglas W. MacDougal uses actual problems from the history of astronomy, as well as original examples, to deepen understanding of how discoveries were made and what they mean. “Newton's Gravity” concentrates strongly on the development of the science of orbital motion, beginning with Galileo, Kepler, and Newton, each of whom is prominently represented. Quotes and problems from Galileo's Dialogs Concerning Two New Sciences and particularly Newton's Principia help the reader get inside the mind of those thinkers and see the problems as they saw them, and experience their concise and typically eloquent writing. This book enables students and curious minds to explore the mysteries of celestial motion without having to know advanced mathematics. It will whet the reader's curiosity to explore further and provide him or her the tools (mathematical or physical) to do so.

Veteran plasma physicist John Brandenburg reveals the new theory that finally accomplishes what Einstein failed to do: the GEM Unification Theory proves the mathematical and physical interrelation of the forces of gravity and electromagnetism! This theory vindicates Einstein's dedication to unifying the fields in the final labor of his life. His quest became legendary, then mythic, until the whole idea was dismissed as myth by other physicists; the gravity-electromagnetism problem pursued by Einstein until his death became regarded like the ancient Greek problem of squaring the circle-an epic puzzle with no solution. But the other physicists were wrong, as Brandenburg shows. It turns out the fields can be unified-the circle can be squared-and this has vast implications for the future of humankind. Brandenburg starts out by tracing the evolution of thought on the two long-term forces of nature, gravity and electromagnetism, from ancient times to the modern day. He shows the intricate interweaving of Einstein's work with that of other physicists, including Sarkharov and his'zero point” theory of gravity and the hidden fifth dimension of Kaluza and Klein. He also traces the surprising, hidden influence of Nikola Tesla on Einstein's life. This book shows how, despite Einstein's errors in the details, the successful GEM Unification Theory is built on his basic hypothesis that gravity and electromagnetic forces could be unified, and that both controlled gravity and a new view of the cosmos follow: hydrogen, the basic building block of the universe, can be unified with the vacuum itself! The universe is self-renewing, a sort of'evergreen cosmos.” Brandenburg describes control of space-time geometry through electromagnetism, and states that faster-than-light travel will be possible in the future. Anti-gravity through electromagnetism is possible, which upholds the basic'flying saucer” design utilizing'The Tesla Vortex.” A must read for any person interested in UFOs and leading-edge physics. See the physics used at Area 51 explained!

Magnetic fields permeate our vast universe, urging electrically charged particles on their courses, powering solar and stellar flares, and focusing the intense activity of pulsars and neutron stars.Magnetic fields are found in every corner of the cosmos. For decades, astrophysicists have identified them by their effects on visible light, radio waves, and x-rays. J. B. Zirker summarizes our deep knowledge of magnetism, pointing to what is yet unknown about its astrophysical applications. In clear, nonmathematical prose, Zirker follows the trail of magnetic exploration from the auroral belts of Earth to the farthest reaches of space. He guides readers on a fascinating journey of discovery to understand how magnetic forces are created and how they shape the universe. He provides the historical background needed to appreciate exciting new research by introducing readers to the great scientists who have studied magnetic fields. Students and amateur astronomers alike will appreciate the readable prose and comprehensive coverage of The Magnetic Universe.

This book brings Einstein's general relativity into action in new ways at scales ranging from the tiny Planck scale to the scale of immense galactic clusters. It presents the case that Einstein's theory of gravity can describe the observed dynamics of galaxies without invoking the unknown “dark matter” required in models based on Newtonian gravity.Drawing on the author's experience as a lecturer and on his own research, the book covers the essentials of Einstein's special and general relativity at a level accessible to undergraduate students. The early chapters provide a compact introduction to relativity for readers who have little or no background in the subject. Hermann Bondi's very transparent approach to special relativity is expanded to resolve the “twin paradox” using only elementary mathematics. In later chapters, general relativity is used to extend the concept of the Planck scale, to address the role of the cosmological term and to analyze the concept of “time machines”.

This is a book that fills the gap between Newtonian gravitation and sophisticated, relativistic theories. It will enable the advanced undergraduate or beginning graduate student to learn the postnewtonian theory that is necessary to account for precise, modern observations. No knowledge of differential geometry is assumed — the required, geometrical ideas are dealt with, as they arise, in their physical context. The book will be useful as an introduction to relativistic theories. Professional physicists and astronomers will be interested in the way the postnewtonian theory is derived as an almost trivial generalization of the Newtonian.