Comments about the article in Nature: Why bad philosophy is stopping progress in physics

Following is a discussion about this article in Nature Vol 641 15 May 2025, by Carlo Rovelli
To study the full text select this link: https://www.nature.com/articles/d41586-025-01465-6

• The text in italics is copied from the article
  
• Immediate followed by some comments
  

In the last paragraph I explain my own opinion.

Reflection

• Reflection 1 -
• Reflection 2 -
• Reflection 3 -

Introduction

Nature seems to have played us for a fool in the past few decades. Much theoretical research in fundamental physics during this time has focused on the search 'beyond' our best theories: beyond the standard model of particle physics, beyond the general theory of relativity, beyond quantum theory. But an epochal sequence of experimental results has proved many such speculations unfounded, and confirmed physics that I learnt at school half a century ago. I think physicists are failing to heed the lessons — and that, in turn, is hindering progress in physics.

It shows that progress in physics, if it exists, is much more difficult as assumed.

Take the 2012 discovery of the Higgs boson using the Large Hadron Collider (LHC) at CERN, Europe's particle-physics laboratory near Geneva, Switzerland. Peter Higgs and François Englert, two of the theorists who had established the underlying theory almost 50 years earlier, shared the 2013 Nobel Prize in Physics for this feat. The Higgs boson was the last particle of the standard model of particle physics to be discovered, and spectacularly confirmed that model, rather than the dozens of theories beyond it. Meanwhile, the apparent absence of evidence for 'supersymmetric' particles in LHC data has disappointed a generation of theoretical physicists who had bet on such particles existing, motivated by speculative theories, including string theory.
Or take the first direct detection of gravitational waves in 2015. This was a spectacular confirmation of Albert Einstein's century-old theory of gravity, general relativity. The 2017 physics Nobel went to three physicists who had made decisive theoretical and experimental contributions to the discovery.
That same year, the near-simultaneous detection of gravitational and electromagnetic signals from the fusion of two neutron stars (the event GW170817) improved scientists' knowledge of the ratio between the speeds of gravitational and electromagnetic waves (which general relativity implies should be the same) by some 14 orders of magnitude. In one fell swoop, this excluded a huge domain of theories beyond general relativity. In a similar vein, the 2020 Nobel Prize in Physics was awarded for work showing that the existence and phenomenology of black holes were in complete agreement with general relativity.
And, finally, take the 2022 physics Nobel, awarded for experiments performed over decades that verified phenomena such as quantum entanglement over great distances, falsifying speculation about theories beyond quantum mechanics. These results are often presented as surprising, but in fact they just confirmed what I was taught in school.

The question is here: what is quantum entanglement and what it is not.
A related question is: When quantum entanglement is observed (established, measured) does that do anything with the mirror particle?

And yet, for decades, every new data point in particle physics or astronomy that seemed to be in some slight tension with established ideas has been announced as a hint of physics 'beyond' current theories. Large communities of physicists have used such hints as a springboard for speculations, producing a forest of papers in the process. But these new data have always turned out to be explicable by established physics, by statistical fluctuations — or even by experimental error.

You might think that this repeated 'no' to wild speculations beyond our best theories would encourage a certain humility in our methodological attitude. Yet I see little evidence for that among many of my fellow theorists, who remain intent on pursuing the next big theory 'beyond' those we have today. Why?

A theory is always(?) some sort of summary.

1. Bad digestion

My hunch is that it is at least partly because physicists are bad philosophers. Scientists' opinions, whether they realize it or not (and whether they like it or not), are imbued with philosophy. And many of my colleagues — especially those who argue that philosophy is irrelevant — have an idea of what science should do that originates in badly digested versions of the work of two twentieth-century philosophers: Karl Popper and Thomas Kuhn.
From Kuhn comes the idea that new scientific theories are not grounded in previous ones: progress instead comes about through 'paradigm shifts', the scientific equivalents of revolutions. Popper, meanwhile, supplies the notion that a theory is scientific only if it is 'falsifiable': if it can be proved wrong by empirical evidence. Superficial readings of Popper and Kuhn, I think, have encouraged several assumptions that have misled a good deal of research: one, that past knowledge is not a good guide for the future and that new theories must be fished from the sky; and two, that all theories that have not yet been falsified should be considered equally plausible and in equal need of being tested.
The history of science suggests that such attitudes are wrong-headed. It is difficult, if not impossible, to think of a major advance in fundamental physics that has emerged from arbitrary hypotheses. They have instead come from two sources, both empirical.
A mirrored view of the countryside with a apple tree. Successful theories of reality are rarely fished from the sky.Credit: Silvia Otte/Getty
The first is new data. Johannes Kepler's insight in the early seventeenth century that the planets move in elliptical, rather than circular, orbits around the Sun, came from observations of anomalies in the movement of Mars. James Clerk Maxwell's nineteenth-century equations of classical electromagnetism stemmed from earlier experiments by Michael Faraday and others. The founding idea of quantum mechanics came in around 1900 from studies of atomic spectroscopy. Quantum chromodynamics, the theory of the strong nuclear force that is one of the underpinnings of the standard model of particle physics, emerged from attempts to bring order to a zoo of newly discovered 'hadron' particles in the 1950s and 1960s. And so on.
The second source of advances is the study of apparent inconsistencies or incoherencies in established knowledge: taking this knowledge seriously, and trying to make it consistent. A celebrated example is Einstein's 1905 special theory of relativity. Special relativity was born from the observation that Maxwell's equations account very well for electromagnetic phenomena, but say that they travel at an absolute velocity: the speed of light. This seemed to be incompatible with a fact understood since investigations by Galileo Galilei in the seventeenth century: that velocity is a relative quantity.
Why even physicists still don't understand quantum theory 100 years on Following the naive reading of Popper and Kuhn, Einstein should have explored modifications of Maxwell's equations or forgone the relativity of velocity. He did the opposite. He trusted past scientific knowledge, kept both Maxwell's equations and the relativity of velocity, and got rid of the apparent contradiction between the two by assuming that both were right and changing something else: the idea that time and simultaneity are absolute. Einstein made the idea that simultaneity depends on how an observer is moving the foundation of a new theory of relativity.
General relativity, which Einstein introduced in 1915, is a product of a similar strategy. It is based on confidence in fundamental knowledge that had already been acquired: special relativity; Newtonian gravity in the relatively weak fields in which it had so far been tested; and Maxwell's theory as a model for circumventing a problem with Newton's gravity, that it seemed to act instantaneously over distances.

Newton's gravity, observed in houshold applications, seems to act instantaneous. In reality this assumption is wrong.

Gravity, like electromagnetism, could also be assumed to have an absolute speed: the speed of light.

Electromagnetism is propagated with the speed of light. Electromagnetic phenomena are typical local phenomena.
Gravity, the speed of gravitational waves, acts over very large distances, has physical nothing to do with the speed of light or photons, but that does not mean that both cannot be the same. IMO the speed of gravity should be identified as cg.

In these and similar cases, progress was made mostly without new data. When, in the sixteenth century, Nicolaus Copernicus explored the possibility that Earth spins and moves around the Sun, rather than the Sun around Earth, he had practically nothing more to lean on than anyone else in astronomy had in the previous millennium. Einstein said that the result of the 1887 Michelson–Morley experiment, which did indeed seem to show that the speed of light is absolute, regardless of who is observing it, was not important to him in deriving special relativity. This assertion is credible, because the Michelson–Morley result is actually irrelevant for deriving special relativity (although it is a validation of the theory). Similarly, the ability of general relativity to explain the anomalous movement of Mercury's perihelion (its point of closest approach to the Sun), which Newtonian gravity could not, worked as a validation of the new theory, but not as a source.
The fabulous case of classical electromagnetism is a little different. Fresh data from Faraday and others were essential, but Maxwell constructed his final synthesis by looking for consistency with previously discovered laws. The new physics was again born from previous knowledge — from taking it seriously as reliable information about reality.

1. Open challenges

'Revolutions' in the history of fundamental physics are thus more conservative than they are often depicted. Kuhn's emphasis on discontinuity has led many scientists to devalue the relevance of past knowledge in making sense of what we do not yet know. Popper's emphasis on falsifiability, meanwhile, originally intended only as a criterion for demarcating a scientific theory, has been misinterpreted as legitimizing the idea that all speculation is equally plausible.
Is there something that we can learn from all of this? What should theoretical physicists do to avoid the miscues, and latch on to the successes, of the past? There I can supply no certain prescription: if there were a known formula for discovery, it would already have been applied.
'Shut up and calculate': how Einstein lost the battle to explain quantum reality

Yet I do think that some reflection on methodology is due. Take the case of supersymmetry. This theory predicted a panoply of particles — one for each particle of the standard model — that the LHC should have found. Supersymmetry had several good motivations; it could, for example, tidy up some of the seemingly arbitrary parameters, including the strength of various forces, needed to make the standard model work. And it could, perhaps, provide an identity for the 'dark' matter that seems to strongly outweigh standard-model matter in the Universe. But now that experimental results from the LHC have clearly shown that these particles are not where so many scientists expected them to be, I think it is fair to say that the enormous amount of human and intellectual resources concentrated on a single, speculative idea was a mistake.
My own view is that there are two clear open challenges for fundamental physics. One comes from observational data: the unknown nature of dark matter. The other comes from the incompleteness of current physics: the lack of an agreed account of what happens in situations in which the quantum aspects of gravity cannot be disregarded. These situations include those inside a black hole where general relativity predicts space-time becomes infinitely curved, or as time is wound back to the very early, hot and compressed Universe. Unlike other problems addressed in fundamental physics, these two open issues are based not on speculations about possibilities beyond what we know, but on actual phenomena we do not understand.
At present, we do not have a consensus on the solution to either problem. But both might be solvable in terms of known physics: general relativity and quantum mechanics. Some tentative quantum theories of gravity such as loop quantum gravity, which I played a part in developing, and the idea that dark matter could be formed by tiny black holes, perhaps stabilized by quantum theory, for instance, are a proof of concept for this possibility.
Does quantum theory imply the entire Universe is preordained? Research directions such as these are not based on guessing new physics. That is the approach taken by string theory, say, which seeks to create a quantum theory of gravity by reinventing the point-like particles of the standard model as one-dimensional objects called strings. Rather, these more conservative approaches are based on trying to extract more from established physics, in the same way that special relativity successfully extracted new knowledge from Galilean relativity and the Maxwell equations.
Like special relativity, these research directions demand conceptual leaps and unfamiliar formalisms to make progress. Both deter many theoretical physicists. Loop quantum gravity, for instance, does away with fields depending on space and time coordinates. But my opinion is that it is in changing concepts and theoretical habits that science can be radical.
There is a healthy sense of crisis in fundamental theoretical physics. Crises are good because they make scientists question underlying assumptions and approaches. It has at times been fashionable to say in theoretical physics that there is a lack of sufficiently wild, completely new ideas. But perhaps the problem is physicists running too much after wild new ideas. New knowledge will come when new data are shown truly not to fit with what we know; or by reflecting in depth on what established theories, such as general relativity and quantum theory, imply when taken together.