Daniel's Blog · Most Theoretical Physicists Are Doing Engineering

Most Theoretical Physicists Are Doing Engineering

Qian Xuesen, while under house arrest during the McCarthy era, wrote Engineering Cybernetics in 1954, drawing the line between a scientist and an engineer. The book was later incorporated deeply into Chinese missile and aerospace doctrine when he successfully returned to China to head the Fifth Academy of the National Defense Ministry (now CASC), and Pakistan’s reported 6:0 air-engagement result against India in May 2025, run on the KJ-500 + J-10C + PL-15 networked kill chain that Chinese systems engineering inherits directly from Qian, is one downstream receipt. The scientist analyses a system that exists. An engineer designs a system that does not. The two are different jobs with different success criteria. The scientist is constrained by what reality returns when you ask it questions. The engineer is constrained by what they want the system to do. The output of one is a description, and the other, an artifact.

Most of what is currently called “theoretical physics” is engineering. The people doing it call themselves scientists but they are not, on Qian Xuesen’s definition, doing the scientist’s job. They are designing models and treating the design as a description of reality. The tell is the moment of “choice of formalism”, when the proposal foregrounds the mathematics’ internal consistency or its aesthetic merit as the reason it should be taken seriously. String theory, ahem. A scientist does not have a choice of formalism. The formalism is whatever it has to be to recover what nature returned. An engineer chooses one because the choice is the work.

The scientist’s job, in fundamental physics, is harder than this and not negotiable. You take the system (the experimental results, the catalogue, all of it) and you ask hard questions about what it means. In fundamental physics those questions are ontological by construction. You cannot conjure a model out of thin air and decide post-hoc what its variables refer to. The variables refer to whatever the experiments forced them to refer to. A proposed equation has to be empirically grounded and rationalised on what reality returned, and its ontology has to stay consistent with itself across the catalogue. If a discipline pretends ontology is “philosophy” and not its problem, it has stopped doing science. We ran the experiments. The data came from nature. Nature has some sort of consistent structure or we would not exist to ask about it. The anti-realist move (“the formalism predicts, the rest is metaphysics”) is defeatism. As one distillation of Jensen Huang’s recent pushback put it, tongue in cheek, I did not wake up a loser.

In my previous essay, The Century-Long Pause in Fundamental Physics, I pointed to how fundamental physicists have stopped pursuing ontology as part of science. Most of the BSM and quantum-gravity programs of the last fifty years are engineered systems being presented as descriptions of reality. Below I list several major programmes that one may have heard in podcasts and YouTube channels like Theory of Everything or Institute of Art and Ideas (IAI). Instead of pursuing the hard problem of ontology, they offer three moves to "solve" the hard problems in fundamental physics. We either add free parameters and fit them, extend an existing symmetry and wait for an experiment that never arrives, or pick a different substrate and hope physics falls out.

Free parameters do the work

Non-local and “plastic” spacetime gravity. These are reformulations of GR with non-local kernels or deformable spacetime structure. The kernel acquires a non-trivial tree of solutions, and the model is then “made to work” by parameter fitting on the kernel, fitting that is never derived but only chosen so the answer comes out. There is no working interface to QM. The engineering tell is that the parameters doing the load-bearing work do not come from anywhere outside the requirement that the output match observation.

Symmetry extension without an empirical anchor

SUSY and GUT. These are motivated proposals (symmetry-completion of the SM, gauge-coupling unification) that had no empirical anchor at the time of proposal. They were dead on arrival in the strict empirical sense, and were kept alive sociologically while the field waited for experiments to formally rule out a sequence of specific predictions. People insisted. We waited. The predictions failed. If these proposals had been presented by non-institutional researchers they would have been dismissed as pure fiction.

Substrate by choice

Superstring and M-theory. It was a cute proposal that was never going to recover from a landscape on the order of 10⁵⁰⁰ vacua. Narrowing that landscape is an unlikely task when the theoretical anchor is neither empirical nor ontologically consistent. There is no rule for picking the vacuum because the construction was never designed to have one.

AdS/CFT....