Beyond the Book
In addition to what you're reading right now, this book also comes with a free access-anywhere Cheat Sheet. To get it, simply go to www.dummies.com and look for String Theory for Dummies Cheat Sheet in the Search box.
If you want to learn more about some of the ideas that laid the basis or string theory, you can also check out Einstein for Dummies by Carlos I. Calle.
Where to Go from Here
The For Dummies books are organized in such a way that you can surf through any of the chapters and find useful information without having to start at Chapter 1. We (naturally) encourage you to read the whole book, but this structure makes it very easy to start with the topics that interest you the most.
If you have no idea what string theory is, then we recommend looking at Chapter 1 as a starting point, then moving through Chapters 2-3 for a basic overview of what we’re talking about. Chapter 4 focuses on laying some foundational ideas about how theoretical science advances. If your physics is rusty, pay close attention to Chapters 5–9, which cover the history and current status of the major physics concepts that pop up over and over again.
If you’re familiar with string theory but want some more details, jump straight to Chapters 10 and 11, where we explain how string theory came about and reached its current status. Chapters 12 and 13 go a bit deeper into the specifics, including the recent insights from the holographic principle. Chapter 14 offers some ways of testing the theory, while Chapters 15–17 take concepts from string theory and apply them to some fascinating topics in theoretical physics.
Some of you, however, may want to figure out what all the recent fuss is with people arguing across the blogosphere about string theory. For that, we recommend jumping straight to Chapter 18, which addresses some of the major criticisms of string theory. Chapters 19 and 20 focus heavily on other theories that may either help expand or replace string theory, so they’re a good place to go from there.
Part 1
Introducing String Theory
IN THIS PART …
Understand the basics of string theory.
Grasp the fundamentals of quantum gravity.
Explore the accomplishments and failures of string theory.
Chapter 1
So What Is String Theory Anyway?
IN THIS CHAPTER
String theory is a work in progress, so trying to pin down exactly what string theory is, or what its fundamental elements are, can be kind of tricky. Regardless, that’s exactly what we try to do in this chapter.
In this chapter, you gain a basic understanding of string theory. We outline the key elements of string theory, which provide the foundation for most of this book. We also discuss the possibility that string theory is the starting point for a “theory of everything,” which would define all of our universe’s physical laws in one simple (or not so simple) mathematical formula. Finally, we look at the reasons why you should care about string theory.
String Theory: Seeing What Vibrating Strings Can Tell Us about the Universe
String theory is a physics theory that models the fundamental particles and interactions in the universe by representing everything in terms of vibrating filaments of energy, called strings. Like all modern physical theories, this image is actually expressed in a precise mathematical language that eventually results in quantitative as well as qualitative predictions.
In this theory, strings of energy represent the most fundamental aspect of nature. String theory also predicts other fundamental objects, called branes, which emerge as a natural generalization of the strings. All the matter in our universe consists of the vibrations of these strings (and branes). One important result of string theory is that gravity is a natural consequence of the theory, which is why scientists believe that string theory may hold the answer to possibly uniting gravity with the other forces that affect matter.
