Void: The Strange Physics of Nothing. By James Owen Weatherall. Yale University Press; 196 pages; $26.

MOST of the universe is empty. So it is natural that a great deal of modern physics concerns nothing—or rather the precise nature of the nothing that permeates the cosmos. Work in the past century in particular has shaken up scientists’ understanding of emptiness. Ideas about gravity and motion put in place by Isaac Newton in the 17th century were overturned by the work of Albert Einstein. The dawn of quantum mechanics revolutionised physicists’ understanding of the very small, but the theory’s conclusions were so counterintuitive that Einstein was never able to reconcile himself with them. James Owen Weatherall, a philosopher, now examines how scientists’ conceptions of supposedly empty space have changed in the light of these convulsions in his latest book, “Void”.

Many people today imagine that, on a molecular scale, the air around them resembles a tumultuous three-dimensional game of billiards. Yet this picture, of molecules of nitrogen, oxygen and other gasses ricocheting through emptiness, is a mere 300 or so years old and has its roots in Newton’s theories. His law of universal gravitation described the attractive force between two masses in a void. But that void is far from obvious. Before the publication of Newton’s “Principia Mathematica” in 1687, two of the most influential thinkers of the Western world, Aristotle and René Descartes, developed theories requiring space (for different reasons) to be filled with stuff of some sort.

In the late 19th century, the work of James Clerk Maxwell also seemed to rule out the notion that a vacuum was truly empty. Maxwell discovered that electricity and magnetism were linked, but he erroneously believed light waves were vibrations in an invisible “aether”. Based on this premise, he and his contemporaries incorrectly reasoned that the speed of light measured in laboratories on Earth could not be its true value since the Earth was moving through space relative to this aether.

Einstein’s work would sweep away this view less than 50 years later. First, in his special theory of relativity, he claimed that the speed of light was the same for all observers, dispensing with the need for the aether. Next, his general theory of relativity would show that space could be curved and textured, like a taut rubber sheet stretched and formed by the masses of planets and stars. Quantum mechanics and quantum electrodynamics (a theory that merges quantum theory with Maxwell’s electromagnetism) would later reveal that even an apparently empty vacuum resembles, at small enough scales, a boiling sea of particles that constantly pop in and out of existence.

These are not easy concepts to describe, and sometimes Mr Weatherall is in danger of losing the uninitiated reader. A diagram or two would have helped. Nonetheless, sending the curious scrambling to Google is forgivable.

More difficult to understand is the book’s failure to mention the work of any female physicists in its pages. The author mentions, for instance, Paul Ehrenfest’s parrot (which the physicist trained to say “But gentlemen, this is not physics!” during discussions of quantum mechanics) but not his wife and collaborator, Tatyana. Also missing from the account is Henrietta Swan Leavitt’s work on Cepheid variables, pulsating stars which would become a yardstick for the expansion of the universe. That means a chapter discussing the possible shapes of the universe consistent with the general theory of relativity ends without discussing what its actual shape might be in the light of such discoveries. These oversights mar an otherwise engaging and interesting account, but perhaps it is natural that a history of space should have a few gaping holes.