String Theory For Dummies. Andrew Zimmerman Jones
String theory, the driving force of 21st-century theoretical physics, could prove to be nothing more than a mathematical illusion that provides some approximate insights into science but isn’t actually the theory that drives the forces of nature.
It’s unclear how long the search for a theory can last without some specific breakthrough. There’s a sense (among some) that the most brilliant physicists on the planet have been spinning their wheels for decades, with only a handful of significant insights, and even those discoveries don’t seem to lead anywhere specific.
The theoretical implications of string theory are addressed in Chapters 10 and 11, while the criticism of the theory rears its ugly head in Chapter 18.
Experimental complications: Can we prove string theory?
Even if a precise version of string theory (or M-theory) is formulated, the question then moves from the theoretical to the experimental realm. Right now, the energy levels that scientists can reach in experiments are probably way too small to realistically test string theory, although aspects of the theory can be tested today.
Theory moves forward with directions from experiment, but the last input that string theory had from experiment was the realization that it failed as a theory in describing the scattering of particles within particle accelerators. The realm string theory claims to explain involves distances so tiny that it’s questionable whether scientists will ever achieve a technology able to probe at that length, so it’s possible that string theory is an inherently untestable theory of nature. (Some versions of string theory do make predictions in testable ranges, however, and string theorists hope that these versions of string theory may apply to our universe.)
You find out some ways to possibly test string theory in Chapter 14, although these are only speculative because right now science doesn’t even have a theory that makes any unique predictions. The best physicists can hope for are some hints that would give some direction to the theoretical search, such as the discovery of certain types of extra dimensions, new cosmological predictions about the formation of our universe, or evidence of the missing supersymmetric particles.
Part 2
The Physics Upon Which String Theory Is Built
IN THIS PART …
Understand the method of science.
Review elements of classical physics.
Apply Einstein’s work in relativity.
Grasp quantum theory basics.
Dive into the Standard Model of particle physics.
Explore cosmology and astrophysics.
Chapter 4
Putting String Theory in Context: Understanding the Method of Science
IN THIS CHAPTER
String theory is at the cutting edge of science. It’s a mathematical theory of nature that, at present, makes few predictions that are directly testable by empirical experiments. This brings up the question of what it takes for a theory to be scientific.
In this chapter, we look a bit more closely at the methods scientists use to investigate nature’s structure. We explore how scientists perform science and some of the ways their work is viewed. We certainly don’t solve any big, philosophical issues in this chapter, but our goal is to make it clear that scientists have differing views about how the nature of science is supposed to work. Although we could write volumes on the evolution of scientific thought throughout the ages, we touch on these topics in just enough detail to help you understand some of the arguments in favor of and against string theory.
Exploring the Practice of Science
Before you can figure out whether string theory is scientific, you have to ask, “What is science?”
Science is the methodical practice of trying to understand and predict the consequences of natural phenomena. This is done through two distinct but closely related means: theory and experiment.
Not all science is created equal. Some science is performed with diagrams and mathematical equations. Other science is performed with costly experimental apparatus. Still other forms of science, while also costly, involve observing distant galaxies for clues to the mystery of the universe.
String theory has spent more than 40 years focusing on the theory side of the scientific equation and, sadly, is relatively lacking on the experimental side, as critics never hesitate to point out. Ideally, the theories developed would eventually be validated by experimental evidence. (See the later sections “The need for experimental falsifiability” and “The foundation of theory is mathematics” for more on the necessity of experimentation.)
The myth of the scientific method
In school, many of us were taught that science follows nice, simple rules called the scientific method. These rules are a classical model of scientific investigation based on principles of reductionism and inductive logic. In other words, you take observations, break them down (the reductionism part), and use them to create generalized laws (the inductive logic part). String theory’s history certainly doesn’t follow this simple model.
The steps of the scientific method students are taught actually change a bit depending on the textbook schools use in a given year, though they generally have mostly common elements. Frequently, they are delineated as a set of bullet points:
Observe a phenomenon: Look at nature.
Formulate a hypothesis: Ask a question (or propose an answer).
Test the hypothesis: Perform an experiment.
Analyze the data: Confirm or reject the hypothesis.
In