Experiments since 1911 prove that the distance between nuclear particles constituting atomic bodies is a hundred thousand times larger than the diameters of these particles. Hence the volumes of all atomic bodies including ourselves are space-like empty, a hundred times more empty than the volume of the solar system. Scores of experiments also prove that space contains electrons and positrons bound to each other by energies of a million electron volts per pair, and form a cubic lattice, named the epola.Based on the epola model of space, this book reveals the physical nature of inertia, gravitation, the spreading of electromagnetic and gravitational actions in space with the velocity of light, and derives their laws. The postulates of quantum and relativity theories are also derived and turned into explainable physical laws. Thus physics is restored as the natural science it had been before it was turned into a science of axiomatic statements and calculations.The book will appeal both to serious scientists and students as well as the general reader interested in scientific explanations of the physical world. Since as a natural science physics deals with the simplest and most basic natural phenomena, this book will be as accessible to the general public as biology books.