The holy grail of theoretical physics is to find the theory of everything that combines all the forces of nature, including gravity. This book addresses the question: how far are we from such discovery? Over the last few decades, multiple roads to finding a quantum theory of gravity have been proposed but no obvious description of nature has emerged in this domain. What is to be made of this situation? This volume probes the state-of-the art in this daunting quest of theoretical physics by collecting critical interviews with nearly forty leading theorists in this field. These broad-ranging conversations give important insights and candid opinions on the various approaches to quantum gravity, including string theory, loop quantum gravity, causal set theory and asymptotic safety. This unique, readable overview provides a gateway into cutting edge research for students and others who wish to engage with the open problem of quantum gravity.

‘The two great achievements in fundamental physics of the 20th century are quantum mechanics, embodied in the standard model of particle physics, and general relativity, Einstein’s theory of gravity. Their reconciliation is the challenge that is addressed in these fascinating interviews with many of the leading experts. Superstring theory, also developed in the 20th century, is the leading candidate to provide the answer, but other ideas are being explored. The wide range of viewpoints presented gives the reader a sense of this profound challenge.’

John H. Schwartz - Harold Brown Professor of Theoretical Physics, Emeritus, Caltech

‘Conversations on Quantum Gravity is a unique resource for students and researchers of quantum gravity, for philosophers and sociologists of science, and for future historians of physics. Jácome Armas has admirably accomplished a herculean task: 37 interviews, peppered with his provocative questions informed by a broad appreciation of the scope of the physics problems and the panoply of approaches to solving them, and copiously referenced to the relevant literature.’

Ted Jacobson - Distinguished University Professor, University of Maryland

‘This book presents an unconventional ten-year ‘long-exposure photograph’ of the evolving research field of quantum gravity. In this field, there is potential for breakthroughs in interlinking diverse approaches, many of which are covered in this book. Thus the book provides an informative read to complement more specialised textbooks. It is suitable for students, researchers and anyone interested in learning what practitioners of quantum gravity consider as the critical obstacles to understanding quantum spacetime.’

Astrid Eichhorn - CP3-Origins, University of Southern Denmark

‘… students and professionals will find the book an excellent portal into the field … Highly recommended.’

A. Spero Source: Choice Magazine

‘As the title states, it consists of experts discussing their research, but at a level which should be accessible to all physicists who have a basic idea as to why a theory of quantum gravity is worth looking for. I recommend it highly to those and to future historians who want to know what those people were really thinking.’

Phillip Helbig Source: The Observatory

‘… excellent for quantum gravity researchers, especially young ones …’

Alexander S. Blum Source: Foundations of Physics