The Fabric of the Cosmos

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The Fabric of the Cosmos

The Fabric of the Cosmos: Space, Time, and the Texture of Reality (2004) is the second book on theoretical physics, cosmology and string theory written by Brian Greene, professor and co-director of Columbia's Institute for Strings, Cosmology, and Astroparticle Physics (ISCAP).^[1]

1 Introduction
2 Summary
3 Reception
4 See also
5 Publication data
6 Notes

[edit] Introduction

Greene begins with the key question: What is reality? Or more specifically: What is spacetime? He sets out to describe the features he finds both exciting and essential to forming a full picture of the reality painted by modern science. In almost every chapter, Greene introduces its basic concepts and then slowly builds to a climax, which is usually a scientific breakthrough. Greene then attempts to connect with his reader by posing simple analogies to help explain the meaning of a scientific concept without oversimplifying the theory behind it.

In the preface, Greene acknowledges that some parts of the book are controversial among scientists. Greene discusses the leading viewpoints in the main text, and points of contention in the end notes. Greene has striven for balanced treatment of the controversial topics. In the end notes, the diligent reader will find more complete explanations relevant to points he has simplified in the main text.

[edit] Summary

[edit] Part 1: Reality's Arena

The main focus of part one is space and time.

Chapter one is an introduction of what is to come later in the book, such as discussions revolving around classical physics, quantum mechanics and cosmological physics.

The second chapter, The Universe and the Bucket, features space as its key point. The question posed by Greene is this: "Is space a human abstraction, or is it a physical entity?" The key thought experiment is a spinning bucket of water, designed to make one think about what creates the force felt inside the bucket when it is spinning. The ideas of Isaac Newton, Ernst Mach, and Gottfried Leibniz on this thought experiment are discussed in detail.

Chapter three, Relativity and the Absolute, makes spacetime its focal point. The question now becomes, "Is spacetime an Einsteinian abstraction or a physical entity?" In this chapter, concepts of both special relativity and general relativity are discussed as well as their importance to the meaning of spacetime.

In chapter four, Entangling Space, Greene explores the revolution of the quantum mechanical era, focusing on what it means for objects to be separate and distinct in a universe dictated by quantum laws. This chapter provides an in-depth study of quantum mechanics, including the concepts of probability waves and interference patterns, particle spin, the photon double slit experiment, and Heisenberg's uncertainty principle. The reader will also be informed of the challenges posed to quantum mechanics that were compiled by Albert Einstein, Boris Podolsky, and Nathan Rosen.

[edit] Part 2: Time and Experience

Part two begins by addressing the issue that time is a very familiar concept, yet it is one of humanity's least understood concepts.

Chapter five, The Frozen River, deals with the question, "Does time flow?" One of the key points in this chapter deals with special relativity. Observers moving relative to each other have different conceptions of what exists at a given moment, and hence they have different conceptions of reality. The conclusion is that time does not flow, as all things simultaneously exist at the same time.

Chapter six, Chance and the Arrow, asks the question, "Does time have an arrow?" The reader learns that the laws of physics apply both moving forward in time and backwards in time. Such a law is called time-reversal symmetry. One of the major subjects of this chapter is entropy. Various analogies are given to illustrate how entropy works and its apparent paradoxes. The climax of the chapter is the co-relation between entropy and gravity, and that the beginning of the universe must be the state of minimum entropy.

In chapters five and six, time has been explained only in terms of pre-modern physics. Chapter seven, Time and the Quantum, gives insights into time's nature in the quantum realm. Probability plays a major role in this chapter because it is an inescapable part of quantum mechanics. The double slit experiment is revisited in a stunning way that reveals both interesting and shocking things about the past. Many other experiments are presented in this chapter, such as the delayed choice quantum eraser experiment. Other major issues are brought to the reader's attention, such as quantum mechanics and experience, as well as quantum mechanics and the measurement problem. Finally, this chapter thoroughly addresses the important subject of decoherence and its relevance towards the macroscopic world.

[edit] Part 3: Spacetime and Cosmology

Part three deals with the macroscopic realm of the cosmos.

Chapter eight, Of Snowflakes and Spacetime, tells the reader that the history of the universe is in fact the history of symmetry. Symmetry and its importance to cosmic evolution becomes the focus of this chapter. Again, general relativity is addressed as a stretching fabric of spacetime. Cosmology, symmetry, and the shape of space are put together in a unique way.

Chapter nine, Vaporizing the Vacuum, introduces the theoretical idea of the Higgs boson. This chapter focuses on the critical first fraction of a second after the big bang, when the amount of symmetry in the universe was thought to have changed abruptly by a process known as symmetry breaking. This chapter also brings into play the theory of grand unification and entropy is also revisited.

Chapter ten, Deconstructing the Bang, makes inflationary cosmology the main point. General relativity and the discovery of dark energy (repulsive gravity) are taken into account, as well as the cosmological constant. Certain problems that arise due to the standard big bang theory are addressed and new answers are given using inflationary cosmology. Such problems include the horizon problem and the flatness problem. Matter distribution throughout the cosmos is also discussed, and the concepts of dark matter and dark energy come full circle.

Chapter eleven, Quanta in the Sky with Diamonds, continues with the topic of inflation, and the arrow of time is also discussed again. The chapter addresses three main developments, the formation of structures such as galaxies, the amount of energy required to spawn the universe we now see, and, of prime importance, the origin of time's arrow.

[edit] Part 4: Origins and Unification

Part four deals with new theoretical aspects of physics, particularly in the field of the author.

Chapter twelve, The World on a String, informs the reader of the structure of the fabric of space according to string theory. New concepts are introduced, including the Planck length and the Planck time, and ideas from The Elegant Universe are revisited. The reader will learn how string theory fills the gaps between general relativity and quantum mechanics so well.

Chapter thirteen, The Universe on a Brane, expands on ideas from chapter twelve, particularly, a branch of string theory called M-theory. This chapter is devoted to speculations on space and time according to M-theory. The collective insights of a number of physicists are presented, including those of Edward Witten and Paul Dirac. The focal point of the chapter becomes gravity and its involvement with extra dimensions. Near the end of the chapter, a brief section is devoted to cyclic cosmology, otherwise known as the cyclic model.

[edit] Part 5: Reality and Imagination

Part five deals with many theoretical concepts, including space and time travel.

Chapter fourteen, Up in the Heavens and Down on the Earth, is about various experiments with space and time. Previous theories are brought back from previous chapters, such as Higg's theory, supersymmetry, and string theory. Future planned experiments are described in an attempt to verify many of the theoretical concepts discussed, including the constitutes of dark matter and dark energy, the existence of the Higg's boson, and the verification of extra spacial dimensions.

Chapter fifteen, Teleporters and Time Machines, is about travelling through space and time using intriguing methods. Quantum mechanics is brought back into the picture when the reader comes across teleportation. Puzzles of time travel are posed, such as the idea of time travel to the past being a possibility. The end of the chapter focuses on worm holes and the theory behind them.

Chapter sixteen, The Future of an Allusion, focuses on black holes and their relationship to entropy. The main idea of this chapter is that spacetime may not be the fundamental make up of the universe's fabric.