Published on August 3, 2025
The Trouble with Physics reads like both a love letter to the field of physics and a pointed indictment of how institutional forces may have misdirected the discipline.
While the book focuses heavily on string theory, it gestures toward a deeper problem within modern theoretical physics. The discipline appears to have lost its touch with reality, and, as Sabine Hossenfelder aptly puts it, many physicists now seem lost in the math. In some quarters, mathematical elegance has replaced empirical evidence as the primary criterion for theoretical validity.
Smolin notes that string theory seminars and conferences seldom discussed how to actually test the theories experimentally. That, I think, should shock every scientist out there. Yet the lack of experimental engagement doesn’t seem to trouble the community nearly as much as it should. As Feynman once remarked, string theory has not produced (i.e. predicted or explained) anything. On the contrary, the framework has been continually modified to avoid contradicting empirical observations. Why does superstring theory posit ten dimensions? Why are exactly six of them curled up?
The answer is simple: because without these assumptions, the theory collapses. String theory is constructed to accommodate existing observations; but to do so, it requires nine spatial dimensions. If we assume only the three we observe, the theory falls apart. And since we’ve never detected any extra dimensions, theorists invoke the “they’re curled up and very small” explanation as a band-aid. This idea is unfalsifiable and appears disconnected from physical reality. Yet without these kinds of ideas, string theory doesn’t work. Rather than acknowledging this failure as a physics theory, its defenders cling to it. As a mathematical framework, however, it has proven remarkably fruitful.
For me, this book highlights the problem with academic bubbles: they don’t stimulate new ideas and original thoughts. These bubbles are governed by grants, tenure and conformity. This is one of the reasons why so much time and money has been invested in (and arguably wasted on) string theory.
The book also presents a number of complex physics ideas, most of which I admittedly hardly grasp. It is definitely interesting to read about supersymmetry, D-branes and gauge theories. But when such concepts are presented without the necessary mathematics, the best you can hope for is walking away with some vague notion of these ideas. This is a problem inherent to popular science, however, and the author still mostly manages to convey the essence of these ideas in relatively clear language.
All in all, it is a genuinely enjoyable book about physics and its contemporary challenges. To finish my thoughts on this book, I’d like to include my favorite segment from the book. It’s funny, but also illustrates how being lost in the math can have quite ridiculous results.
In a supersymmetric theory there will be a fermion that partners with the Higgs, called the Higgsino. (In supersymmetry-theory convention, the superpartners of fermions begin with an ‘s,’ like the selectron, while the superpartners of bosons end in ‘ino.’) […] A theory cannot be partly supersymmetric. If one particle has a superpartner, they all must. Thus, each quark comes with a bosonic partner, a squark. The photon is partnered with a new fermion, the photino. […] Unfortunately, no one has ever successfully postulated a supersymmetry holding between two known particles … Not only are there squarks and sleptons and photinos, there are also sneutrinos to partner the neutrinos, Higgsinos with the Higgs, and gravitinos to go with the gravitons. Two by two, a regular Noah’s ark of particles. Sooner or later, tangled in the web of new snames and naminos, you begin to feel like Sbozo the clown. Or Bozo the clownino. Or swhatever.
Smolin, L. (2008). The Trouble with Physics: The Rise of String Theory, the Fall of a Science, and What Comes Next. Penguin.