The instant New York Times bestseller Quanta and Fields , the second book of Sean Carroll’s already internationally acclaimed series The Biggest Ideas in the Universe , is an adventure into the bare stuff of reality.   Sean Carroll is creating a profoundly new approach to sharing physics with a broad audience, one that goes beyond analogies to show how physicists really think. He cuts to the bare mathematical essence of our most profound theories, explaining every step in a uniquely accessible way.   Quantum field theory is how modern physics describes nature at its most profound level. Starting with the basics of quantum mechanics itself, Sean Carroll explains measurement and entanglement before explaining how the world is really made of fields. You will finally understand why matter is solid, why there is antimatter, where the sizes of atoms come from, and why the predictions of quantum field theory are so spectacularly successful. Fundamental ideas like spin, symmetry, Feynman diagrams, and the Higgs mechanism are explained for real, not just through amusing stories. Beyond Newton, beyond Einstein, and all the intuitive notions that have guided homo sapiens for millennia, this book is a journey to a once unimaginable truth about what our universe is. Praise for Quanta and Fields: “Readers will be electrified by his discussion of wave functions, entanglement, fields, and so much more. From the most infinitesimal of subatomic particles to the seemingly vast infinities of the universe’s great expanse, Carroll’s latest inquiry illuminates, well, everything.” — Booklist "In that void between hand-wavy popular science and academic textbook, this modern, informative and engaging account of quantum physics ticks all the boxes. Carroll the Explainer at his very best." — Jim Al-Khalili Sean Carroll is Homewood Professor of Natural Philosophy at Johns Hopkins University, and Fractal Faculty at the Santa Fe Institute. He is host of the Mindscape podcast, and author of From Eternity to Here , The Particle at the End of the Universe , The Big Picture , and Something Deeply Hidden . He has been awarded prizes and fellowships by the National Science Foundation, NASA, the American Institute of Physics, the Royal Society of London, and many others. He lives in Baltimore with his wife, writer Jennifer Ouellette. ONE Wave Functions As the nineteenth century drew to a close, you would have forgiven physicists for hoping that they were on track to understand everything. The universe, according to this tentative picture, was made of particles that were pushed around by fields. The idea of fields filling space had really taken off over the course of the 1800s. Earlier, Isaac Newton had presented a beautiful and compelling theory of motion and gravity, and Pierre-Simon Laplace had shown how we could reformulate that theory in terms of a gravitational field stretching between every object in the universe. A field is just something that has a value at each point in space. The value could be a simple number, or it could be a vector or something more complicated, but any field exists everywhere through space. But if all you cared about was gravity, the field seemed optional-a point of view you could choose to take or not, depending on your preferences. It was equally okay to think as Newton did, directly in terms of the force created on one object by the gravitational pull of others without anything stretching between them. That changed in the nineteenth century, as physicists came to grips with electricity and magnetism. Electrically charged objects exert forces on each other, which is natural to attribute to the existence of an electric field stretching between them. Experiments by Michael Faraday showed that a moving magnet could induce electrical current in a wire without actually touching it, pointing to the existence of a separate magnetic field, and James Clerk Maxwell managed to combine these two kinds of fields into single a theory of electromagnetism, published in 1873. This was an enormous triumph of unification, explaining a diverse set of electrical and magnetic phenomena in a single compact theory. "Maxwell's equations" bedevil undergraduate physics students to this very day. One of the triumphant implications of Maxwell's theory was an understanding of the nature of light. Rather than a distinct kind of substance, light is a propagating wave in the electric and magnetic fields, also known as electromagnetic radiation. We think of electromagnetism as a "force," and it is, but Maxwell taught us that fields carrying forces can vibrate, and in the case of electric and magnetic fields those vibrations are what we perceive as light. The quanta of light are particles called photons, so we will sometimes say "photons carry the electromagnetic force." But at the moment we're still thinking classically. Take a single charged particle, like an electron. Left sitting by itself, it will have an