Preface

  This is a book about gravity. Gravity is what causes massive objects to fall towards each other. It's gravity that causes apples to fall from trees, and it was gravity that caused the Earth to form. Gravity is the most familiar of all the fundamental forces of nature, yet the true way in which gravity works is far from obvious. In reality, the phenomenon we refer to as 『gravity』 is deeply tied up with the nature of space and time. This means that a modern understanding of gravity doesn’t just tell us how objects in the Universe move, it also allows us to understand the behaviour of the very space and time that make up the fabric of the Universe itself.

  The purpose of this book is to give the reader a very brief introduction to various diferent aspects of gravity. We start by looking at the way in which the theory of gravity developed historically, before moving on to an outline of how it is understood by scientists today. We will then consider the consequences of gravitational physics on the Earth, in the Solar System, and in the Universe as a whole. The final chapter describes some of the frontiers of current research in theoretical gravitational physics.

  By the end, I intend to have conveyed to the reader not only what gravity is, but how the study of gravity has led scientists to reach extraordinary conclusions about the nature of space, time, and the Universe in which we live.