In July 2012, after I sent the first-draft manuscript for a book titled God and the Atom: From Democritus to the Higgs Boson to the publisher, a dramatic news conference was held at the European Organization for Nuclear Research (CERN) in Geneva that made headlines around the world. It was announced that two experiments, each costing about a billion dollars and involving thousands of scientists from dozens of nations, had independently confirmed, with high empirical significance, the existence of an elementary particle called the Higgs boson.

This Higgs boson had been proposed forty-eight years earlier to provide the mechanism by which other elementary particles obtain mass. Its discovery corroborated the standard model of elementary particles, which was developed in the 1970s. Since then, the standard model has successfully described the basic constituents of subatomic matter and the forces by which they interact to construct the physical universe. No empirical violation of the standard model has yet been reported.

Fortunately, I was able to work a full account of the Higgs discovery into God and the Atom, which was published in 2013.

In March 2014, I had submitted the first draft of the manuscript for the present book to the publisher when this story was repeated. A news conference at Harvard attracted similar worldwide attention, making front pages everywhere. An international collaboration working at the South Pole announced that it had observed, with high significance, a type of polarization in the cosmic microwave background called “B-mode” that was interpreted as a signal for gravitational waves produced by quantum fluctuations in space-time when the universe first came into existence 13.8 billion years ago.

Most media reports failed to mention that the result was provisional, that all other explanations have not been ruled out, and that the result remains to be independently verified. However, if the observation passes these tests, the implication is momentous.

B-mode polarization in the early universe had been predicted by a cosmological model, first proposed in 1980, called inflation. According to inflation, during the first tiny fraction of a second after it came into being, the universe expanded exponentially by many orders of magnitude. The model solved a number of outstanding problems in cosmology and has since passed several rigorous tests that could have falsified it.

Inflation strongly implies that our universe is not alone but is just one of an unlimited number of other universes in what has been termed the multiverse. This multiverse exists endlessly in space and time. It had no beginning, no creation. It always existed and always will.

Once again I was able to include this discovery in the present book, which contains a detailed discussion of the cosmic microwave background (CMB). We will see how precise measurements of the CMB by extraordinary instruments in space and on Earth have provided us with a deep knowledge of the earliest moments of our universe and its evolution to the present day.

The aim of God and the Multiverse is to show how the current picture of our vast universe and the real possibility of multiple universes developed over the millennia since humans first looked at the sky and asked what was out there. We will examine how the ancient notion of a supernatural creation arose to explain what eventually became explicable by purely natural processes.

The story is necessarily a long one, and the reader is asked to be patient and follow step-by-step the chronological progression as humanity's view of the cosmos expanded from a flat Earth with the heavens above and waters below to a hundred billion galaxies, each with a hundred billion stars, and countless planets capable of sustaining life, and then on to an infinite and eternal multiverse.