Key Moments
What's Going Wrong in Particle Physics? (This is why I lost faith in science.)
Sabine HossenfelderKey Moments
Particle physics relies on overcomplicated models and unsupported predictions, failing to progress.
Key Insights
Particle physics has a long history of making predictions for new particles (supersymmetry, dark matter, etc.) that have consistently failed to be observed.
The Standard Model of particle physics is well-tested and agrees with all available data, yet physicists continue to develop complex, unfalsifiable extensions.
Many proposed 'problems' in particle physics, such as 'grand unification' or the 'hierarchy problem,' are aesthetic preferences rather than genuine scientific issues.
The practice of constantly modifying theories to accommodate failed predictions, rather than learning from them, resembles overfitting data and is not good science.
Genuine progress in physics has historically come from necessary changes to theories to resolve inconsistencies, not from adding complexity without evidence.
The current approach in particle physics is financially unsustainable and risks collapsing funding due to a lack of demonstrable progress.
A Pattern OF FAILED PREDICTIONS
News from particle physics often revolves around either the failure to find expected particles or the lack of findings from new searches. For about 50 years, starting in the 1970s with the completion of the Standard Model, physicists have predicted the existence of numerous particles like supersymmetric partners, axions, sterile neutrinos, and WIMPs. Despite extensive experimental searches across decades and various facilities, none of these predicted particles have ever been detected, leading to a long list of unfulfilled expectations.
THE STANDARD MODEL AND THE LURE OF NEW SYMMETRIES
The Standard Model, which successfully describes fundamental particles and their interactions, was experimentally confirmed with the discovery of particles like the W and Z bosons, the top quark, and the Higgs boson. Despite its success, many particle physicists felt it was incomplete, particularly its inability to unify the electromagnetic, strong, and weak nuclear forces into a single Grand Unified Theory (GUT). This desire for unification, driven by a belief in the power of symmetry principles in physics, led to theories that made predictions beyond the Standard Model's tested ranges.
THE RISE OF PSEUDO-PROBLEMS AND CONVOLUTED THEORIES
Attempts to address perceived shortcomings, like the 'strong CP problem' or the 'hierarchy problem,' led to the postulation of new particles and theories, such as axions and supersymmetry (SUSY). The strong CP problem, concerning a parameter being zero or very small, spurred the axion hypothesis, which was quickly ruled out by observations but subsequently modified. Similarly, supersymmetry, initially predicting partner particles with similar masses to known ones, was amended to higher masses to escape early experimental falsification, yet consistently failed to be detected at higher-energy colliders.
OVERFITTING AND THE DEPARTURE FROM SCIENTIFIC METHOD
The core issue, as illustrated by the concept of overfitting in data analysis, is that particle physicists often create overly complex models that fit existing data but make numerous, unfalsifiable predictions. When these predictions fail, instead of discarding the model, it is modified or complicated further to accommodate new, limited experimental ranges. This iterative process, where theories are constantly adjusted to avoid direct contradiction with data rather than driven by new evidence or internal inconsistencies, deviates from sound scientific practice, resembling the creation of 'made-up stories'.
THE DISTINCTION BETWEEN REAL AND PSEUDO-PROBLEMS
Many of the problems particle physicists attempt to solve are not fundamental issues preventing progress but rather aesthetic preferences or 'pseudo-problems.' These include the desire for grand unification or explanations for why certain parameters have specific values, which do not hinder the predictive power of the well-verified Standard Model. Real problems in physics are typically those that manifest as inconsistencies with data or internal contradictions within a theory, which, when addressed, lead to genuine theoretical advancements, as seen with the Higgs boson or neutrinos.
CONSEQUENCES AND THE UNSUSTAINABLE FUTURE
The current methodology in particle physics, characterized by a high volume of papers, conferences, and numerous wrong predictions, is not a sustainable path for scientific discovery. While some argue that progress takes time, the issue is not the duration but the consistent failure of predictions. The lack of robust, successful predictions means that funding for particle physics is increasingly at risk. Without a return to rigorous methods focused on necessary theoretical changes, the field may face a collapse in funding and interest.
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Particle physicists often invent new particles or theories based on aesthetic preferences or 'pseudo-problems,' rather than necessary changes to existing models. When these predictions are falsified by experiments, they amend the models rather than questioning the initial premise, leading to a pattern of incorrect predictions.
Topics
Mentioned in this video
A theory that describes all known fundamental particles and their interactions. It was completed in the 1970s and has been experimentally confirmed, but physicists believe there is more to find beyond it.
Fundamental particles discovered in 1983 at CERN. Their discovery was a key confirmation of the Standard Model.
A fundamental particle discovered in 1995 at Fermilab, further confirming the Standard Model.
The last fundamental particle predicted by the Standard Model, discovered in 2012. Its discovery was seen as the final confirmation of the Standard Model.
Theoretical frameworks that aim to combine the electromagnetic, strong, and weak nuclear forces into a single unified force. They were explored in the 1970s.
A predicted phenomenon where a proton spontaneously transforms into lighter particles. Experiments since the 1980s have looked for proton decay, which is a prediction of some Grand Unified Theories, but have not found evidence for it.
A problem in particle physics concerning why the Theta parameter in the strong nuclear force is experimentally found to be zero or very small, which would otherwise violate CP symmetry.
A theoretical framework postulating that all fundamental particles have a partner particle. Initial models with similar masses were ruled out, and subsequent amendments with higher masses have also failed to yield experimental confirmation.
The question of why the mass of the Higgs boson is so much smaller than the Planck Mass. Supersymmetry was claimed to address this, but the speaker argues it does not.
A proposed fundamental unit of mass in quantum gravity theories, significantly larger than the Higgs boson mass, which is relevant to the hierarchy problem.
A popular candidate for Dark Matter particles that have not been found by experiments since the 1980s, with particle physicists repeatedly adjusting theories about their interaction strength.
An experiment that looked for light fermionic dark matter and did not find it.
An experiment that searched for light WIMPs and did not find them.
An experiment that looked for sub-GeV dark matter and did not find it.
Used as an example of a falsifiable but not scientific claim, illustrating the difference between a testable hypothesis and a scientifically valid one.
An experiment that did not find evidence for WIMP annihilation.
Mentioned as a phenomenon that took half a century to directly detect, used as an example of how long scientific discoveries can take.
A phenomenon explained by the existence of three generations of quarks, cited as an example of a necessary change to a model.
An experiment that searched for a fifth force and did not find it.
A necessary theoretical development for which certain particles (like those predicted by the Dirac equation) were required.
Fields that require explanations for observations, potentially involving dark matter or modifications to gravity.
The European Organization for Nuclear Research, where the W and Z bosons were discovered. It is also home to the Large Hadron Collider.
A particle collider at CERN that tested supersymmetric models in the 1990s, with falsified predictions.
Mentioned as a source for lists of unsolved problems in physics, many of which the speaker categorizes as 'pseudo-problems'.
Mentioned as a figure whose theories are understood as realizations of symmetries, though he didn't explicitly use symmetry arguments himself.
Physicist who proposed the Axion particle in 1978 and later, in 1982, proposed the 'femalon'.
Philosopher of science whose ideas on falsifiability are discussed. The speaker emphasizes that falsifiability alone does not make a hypothesis scientific.
A hypothetical particle proposed to solve the strong CP problem. Early versions were ruled out by experimental observations, and subsequent versions, like the 'invisible axion', have also not been detected.
Mentioned as an example of a particle whose hypothesis took over 30 years to confirm, contrasting with the current approach in particle physics.
A particle collider that was expected to find supersymmetric particles but did not.
A popular class of hypothesized particles, including WIMPs, that are theorized to exist but have not been detected by numerous experiments since the 1980s.
A hypothetical type of neutrino that experiments like Stereo have looked for without success.
A particle collider where supersymmetric particles were expected to show up but did not.
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