A spacetime appetizer -- Relatively speaking -- Einstein on trial -- Wave talk and bar fights -- The lives of stars -- Clockwork precision -- Laser quest -- The path to perfection -- Creation stories -- Cold case -- Gotcha -- Black magic -- Nanoscience -- Follow-up questions -- Space invaders -- Surf's up for Einstein wave astronomy

On 14 September 2015, after 50 years of searching, gravitational waves were detected for the first time and astronomy changed for ever. Until then, investigation of the universe had depended on electromagnetic radiation: visible light, radio, X-rays and the rest. But gravitational waves – ripples in the fabric of space and time – are unrelenting, passing through barriers that stop light dead. At the two 4-kilometre long LIGO observatories in the US, scientists developed incredibly sensitive detectors, capable of spotting a movement 100 times smaller than the nucleus of an atom. In 2015 they spotted the ripples produced by two black holes spiralling into each other, setting spacetime quivering. This was the first time black holes had ever been directly detected – and it promises far more for the future of astronomy. Brian Clegg presents a compelling story of human technical endeavour and a new, powerful path to understand the workings of the universe.

The detection of gravitational waves--ripples in spacetime--has already been called the scientific coup of this century. Govert Schilling recounts the struggles that threatened to derail the quest and describes the detector's astounding precision, weaving far-reaching discoveries about the universe into a gripping story of ambition and perseverance.

This book is devoted to researchers who would like to investigate interactions among gravitational waves and matter fields beyond linear order, including the phenomena of memory effects, gravitational Faraday rotation, soft theorems, and formations of spacetime singularities due to the mutual focus of gravitational waves. Readers only require a basic understanding of general relativity to understand the materials.The book starts with an overview on the fundamentals of the Newman-Penrose formalism and a brief introduction to distribution theory, with which the author systematically develops a mathematical description of spacetimes of colliding plane waves. Then, the author presents a frame-independent definition of polarization of a plane gravitational wave in a curved spacetime, studies in detail the gravitational Faraday rotation of two plane gravitational waves, and shows that each of them can serve as a medium to the other precisely due to their nonlinear interactions. Exact solutions are also presented, which represent a variety of models including the collisions of two plane gravitational waves and the collisions of a plane gravitational wave with a dust shell, a massless scalar wave, an electromagnetic wave, or a neutrino wave. The formation of spacetime singularities due to nonlinear interactions and the effects of gravitational wave polarization on the nature of singularities are also explored.

In physics, gravitational waves are ripples in the curvature of space-time which propagate as waves, travelling outward from the source. Predicted in 1916 by Albert Einstein to exist on the basis of his theory of general relativity, gravitational waves theoretically transport energy as gravitational radiation. Sources of detectable gravitational waves could possibly include binary star systems composed of white dwarfs, neutron stars, or black holes. The existence of gravitational waves is a possible consequence of the Lorentz invariance of general relativity since it brings the concept of a limiting speed of propagation of the physical interactions with it. Gravitational waves cannot exist in the Newtonian theory of gravitation, in which physical interactions propagate at infinite speed. Although gravitational radiation has not been directly detected, there is indirect evidence for its existence. For example, the 1993 Nobel Prize in Physics was awarded for measurements of the Hulse-Taylor binary system which suggest that gravitational waves are more than theoretical concept. Various gravitational-wave detectors are currently under construction or are in operation, such as The Advanced LIGO which began observations in September 2015. This book discusses the theories, concepts and experiments that pertain to gravitational waves.

Gravitational waves were first predicted by Albert Einstein in 1916, a year after the development of his new theory of gravitation known as the general theory of relativity. This theory established gravitation as the curvature of space-time produced by matter and energy. To be discernible even to the most sensitive instruments on Earth, the waves have to be produced by immensely massive objects like black holes and neutron stars which are rotating around each other, or in the extreme situations which prevail in the very early ages of the Universe. This book presents the story of the prediction of gravitational waves by Albert Einstein, the early attempts to detect the waves, the development of the LIGO detector, the first detection in 2016, the subsequent detections and their implications. All concepts are described in some detail, without the use of any mathematics and advanced physics which are needed for a full understanding of the subject. The book also contains description of electromagnetism, Einstein’s special theory and general theory of relativity, white dwarfs, neutron stars and black holes and other concepts which are needed for understanding gravitational waves and their effects. Also described are the LIGO detectors and the cutting edge technology that goes into building them, and the extremely accurate measurements that are needed to detect gravitational waves. The book covers these ideas in a simple and lucid fashion which should be accessible to all interested readers. The first detection of gravitational waves was given a lot of space in the print and electronic media. So, the curiosity of the non-technical audience has been aroused about what gravitational waves really are and why they are so important. This book seeks to answer such questions.

Since Einstein first described them nearly a century ago, gravitational waves have been the subject of more sustained controversy than perhaps any other phenomenon in physics. These as yet undetected fluctuations in the shape of space-time were first predicted by Einstein's general theory of relativity, but only now, at the dawn of the twenty-first century, are we on the brink of finally observing them. Daniel Kennefick's landmark book takes readers through the theoretical controversies and thorny debates that raged around the subject of gravitational waves after the publication of Einstein's theory. The previously untold story of how we arrived at a settled theory of gravitational waves includes a stellar cast from the front ranks of twentieth-century physics, including Richard Feynman, Hermann Bondi, John Wheeler, Kip Thorne, and Einstein himself, who on two occasions avowed that gravitational waves do not exist, changing his mind both times. The book derives its title from a famously skeptical comment made by Arthur Stanley Eddington in 1922--namely, that "gravitational waves propagate at the speed of thought." Kennefick uses the title metaphorically to contrast the individual brilliance of each of the physicists grappling with gravitational-wave theory against the frustratingly slow progression of the field as a whole. Accessibly written and impeccably researched, this book sheds new light on the trials and conflicts that have led to the extraordinary position in which we find ourselves today--poised to bring the story of gravitational waves full circle by directly confirming their existence for the very first time.

The sixteen papers collected in this volume are expanded and revised versions of talks delivered at the Second International Conference on the Ontology of Spacetime, organized by the International Society for the Advanced Study of Spacetime (John Earman, President) at Concordia University (Montreal) from 9 to 11 June 2006. Most chapters are devoted to subjects directly relating to the ontology of spacetime. The book starts with four papers that discuss the ontological status of spacetime and the processes occurring in it from a point of view that is first of all conceptual and philosophical. The focus then slightly shifts in the five papers that follow, to considerations more directly involving technical considerations from relativity theory. After this, Time, Becoming and Change take centre stage in the next five papers. The book ends with two excursions into relatively uncharted territory: a consideration of the status of Kaluza-Klein theory, and an investigation of possible relations between the nature of spacetime and condensed matter physics, respectively. - Space and time in present-day physics and philosophy - Relatively low level of technicality, easily accessible - Introduction from scratch of the debates surrounding time - Broad spectrum of approaches, coherently represented

This fascinating book provides an accessible and up-to-date overview of modern cosmology. In particular, the book discusses the formation of the Cosmic Microwave Background and the evolution of large scale structures in the universe, the distribution of galaxies and clusters of galaxies on very large distance scales. Following a brief introduction, the authors describe the scientific method – how science is done. They then discuss observational cosmology, the instruments and what observations can be done with them, and what is derived from those observations. After discussing the constituents of the universe, including dark matter and dark energy, the authors provide an outline of the forces that shape the universe, with particular emphasis on gravitation. Following this, the reader is taken on a journey in time from the present day back to the very beginning of the universe, a period called inflation, which sets the initial conditions for the subsequent evolution of the universe. The book ends with a brief chapter on what lies beyond. Written by two experts, the book is aimed at the interested lay-person with little or no physics background, but an interest in modern cosmology.

Quantum gravity (QG) is a field of theoretical physics that seeks to describe the force of gravity according to the principles of quantum mechanics. The current understanding of gravity is based on Albert Einstein's general theory of relativity, which is formulated within the framework of classical physics. On the other hand, the nongravitational forces are described within the framework of quantum mechanics, a radically different formalism for describing physical phenomena based on probability. The necessity of a quantum mechanical description of gravity follows from the fact that one cannot consistently couple a classical system to a quantum one. In physics, gravitational waves are ripples in the curvature of space-time which propagate as waves, travelling outward from the source. Predicted in 1916 by Albert Einstein to exist on the basis of his theory of general relativity, gravitational waves theoretically transport energy as gravitational radiation. Sources of detectable gravitational waves could possibly include binary star systems composed of white dwarfs, neutron stars, or black holes. The existence of gravitational waves is a possible consequence of the Lorentz invariance of general relativity since it brings the concept of a limiting speed of propagation of the physical interactions with it. Gravitational waves cannot exist in the Newtonian theory of gravitation, in which physical interactions propagate at infinite speed. Although gravitational radiation has not been directly detected, there is indirect evidence for its existence. For example, the 1993 Nobel Prize in Physics was awarded for measurements of the Hulse-Taylor binary system which suggest that gravitational waves are more than theoretical concept. Various gravitational-wave detectors are currently under construction or are in operation, such as The Advanced LIGO which began observations in September 2015. This book discusses the current theories, concepts and experiments that pertain to quantum gravity and gravitational waves.