Why physics still matters
Part 1 of 5: What is physics?
[Part 2 →]
What is physics? In a world of machine learning, results-oriented education, and growing skepticism about the value of basic research, this question daily takes on increasing urgency. Why should billions of dollars continue to flow from taxpayers into physics departments, when big data and machine learning promise quicker answers to immediate technological challenges? Why should a bright undergraduate choose to pursue a physics PhD, instead of making much more money in finance, or directly improving people’s lives through biology or medicine? If physics is to survive as a discipline, we need compelling answers to these questions.
The standard answer rests on two claims. First of all, physics is intrinsically valuable, because it reveals the most fundamental principles that govern how the whole world works. This is in fact the reason why most people study physics -- especially theoretical physics. They want to unlock the mysteries of the cosmos. The second claim is that this kind of understanding is required for technological advancement. All of modern life, from airplanes to iPhones, depends on the application of principles discovered by physicists. This is the justification typically given to funding agencies and the general public, which met with great success particularly during the Cold War.
The growing crisis in physics comes from the fact that the actual activity of physicists appears increasingly irrelevant to both of these stated goals.1 The abstractness of cutting-edge theory, which requires years of advanced mathematical training to begin to be comprehended, makes the connection between the fundamental principles and the everyday facts they are supposed to explain seem almost implausibly tenuous to the beginner. Added to this is a cultural context in which the very idea of a rational system of “laws” mysteriously governing the inanimate world seems absurd. Where are these laws located? And who gave them their authority?
The distance between current theoretical advances and everyday phenomena also weakens the second claim. It is difficult to explain to the general public how a billion-dollar investment in a particle accelerator will lead to technology that makes life tangibly better for them. Physicists often find themselves forced to fall back on vague generalities about how science necessarily produces technological progress. When you are competing against biologists who can show videos of human tissues they are growing on plastic chips, this argument starts to look pretty weak.
For physics to continue to flourish in the 21st century, we need a stronger argument for each of these two claims. A robust account of the kind of knowledge that physics produces is required not only to recruit graduate students and secure funding, but also to help us set our own priorities as physicists in a way that leads to lasting and meaningful results.
This situation presents us with a marvelous opportunity for growth in methodological self-awareness. The challenge of defending the intrinsic and the instrumental value of the discipline forces us to shed a whole collection of problematic assumptions that we have unquestioningly absorbed over the course of our education. Unlearning dogmas that have become second-nature is always painful, but this pain is a necessary step towards a mature and nuanced defense of the enduring significance of our field.
The core of the account to be presented in the next four installments will be drawn from Aristotle’s classification of the types of knowledge, as developed by Boethius and Aquinas over the course of the Middle Ages and applied to modern physics by the philosophers Jacques Maritain, Nancy Cartwright and Stanley Jaki. The Aristotelian tradition has the advantage of a broad and immediate appeal across cultures and centuries, with major contributions made by Jews, Muslims and Christians throughout the Middle Ages, and a recent resurgence within academic philosophy both in the West and in China. This universality stems from the emphasis this tradition gives to immediate experience as the starting point for all philosophical reflection, providing a basis for synthesizing the highest reaches of philosophical and scientific investigation with the ordinary “common-sense” perspective on the world that governs the way people actually behave and work.
The final section on the new directions of 21st-century physics comes out of my own research experience, applying the philosophical framework of the first three chapters to explain what I find important and exciting about the areas of physics to which I have personally contributed. The major external source for that chapter is a famous essay by physicist Philip Anderson, whose content has yet to be fully digested.
[Part 2 →]
See Sabine Hossenfelder, Lost in Math (New York: Basic Books, 2018) for a compelling and accessible inside perspective on this “crisis.”