Where is physics going? | Sabine Hossenfelder, Bjørn Ekeberg and Sam Henry

The discussion begins with Philip Ball introducing the topic of whether the standard model, which has been the foundation of our understanding of the universe since the 1970s, needs revision. Despite its success in predicting the existence of quarks, force particles, and the Higgs boson, the standard model fails to explain gravity, dark energy, and dark matter. Recent evidence suggests a new force that could potentially overturn the entire theory. The panel includes Sam Henry, a particle physicist; Sabina Hossenger, a theoretical physicist; and Bjorn Eckebech, a philosopher of science. They will explore the possibility of a paradigm shift in physics and the implications of the standard model's limitations.

Sam Henry discusses the lack of discoveries beyond the standard model, such as supersymmetric particles and dark matter, despite expectations. He highlights the muon g-2 experiment, which found a discrepancy between the measured value of the muon's magnetic moment and the standard model prediction, potentially indicating new physics. However, Henry also notes that the lack of clear predictions from theories like supersymmetry has made it difficult to find evidence for new physics, and there's a need for more exciting developments in the field.

Sabina Hossenger argues that calling the standard model 'flawed' is too harsh, as it works perfectly well within its domain. However, she acknowledges its shortcomings, such as the lack of a gravitational component and the mystery surrounding neutrinos, which come in only one handedness, unlike other particles. Hossenger suggests that the real paradigm shift might come from a better understanding of quantum mechanics and the measurement process, which are foundational to the standard model but not fully understood.

Bjorn Eckebech points out the existence of two standard models: one in particle physics and another in cosmology, based on the big bang theory and including dark matter and dark energy. He argues that the cosmological standard model appears deeply flawed, yet persists due to its entrenchment and the difficulty of developing an alternative. Eckebech suggests that physics, particularly cosmology, has become path dependent on the standard model, making it challenging to consider fundamental changes.

The panelists discuss the perceived crisis in physics and the slowdown in progress, particularly in fundamental physics and particle physics. Sabina Hossenger explains that as scientific disciplines mature, progress becomes harder to achieve. She criticizes the theoretical physics community for not being careful enough in developing theories, leading to a disconnect between theory and experiment. Sam Henry adds that while progress hasn't stalled, it's not as rapid or as groundbreaking as hoped, and there's a need for reflection on the relationship between experimental and theoretical physics.

The conversation turns to the impact of astrophysical observations, such as those related to dark energy, on theoretical physics. The panelists agree that these observations have introduced new problems for high-energy physicists, who were unprepared for the discovery of dark energy in the 1990s. The discussion highlights the challenge of reconciling theoretical predictions with observational data and the need for new theories to explain these discrepancies.

The panelists delve into the muon g-2 anomaly, which suggests the presence of new physics beyond the standard model. Sam Henry explains the significance of the muon as a probe for new physics and the challenges in interpreting the g-2 results. Sabina Hossenger criticizes the theoretical community's ability to quickly provide explanations for anomalies, arguing that this flexibility renders predictions worthless. The discussion underscores the need for a more rigorous approach to theory development.

Bjorn Eckebech discusses the role of the philosophy of science in addressing fundamental questions in physics and cosmology. He highlights the importance of questioning core assumptions and the limitations of current theoretical frameworks. Sabina Hossenger agrees, emphasizing the need for more critical examination of theory development methods. The panelists consider the value of philosophical insights in guiding the direction of future research and the potential for paradigm shifts in physics.

The discussion focuses on the dark matter problem, with Sabina Hossenger explaining the indirect evidence for its existence and the challenges in detecting it. She criticizes the theoretical motivations behind dark matter candidates like WIMPs and axions, arguing that they are based on theoretical convenience rather than empirical evidence. The panelists consider alternative theories like Modified Newtonian Dynamics (MOND) and the need for more fundamental questions in physics.

Bjorn Eckebech discusses the potential implications of a paradigm shift in physics, arguing that minor changes, like replacing one block in a Jenga tower, may not affect many lives outside the scientific community. However, more radical shifts, like a new understanding of fundamental forces or the universe's origin, could have significant cultural impacts. He notes that the power of a theory lies in its ability to explain phenomena, and modern physics has become less effective in this regard.

Sam Henry shares his perspective on the quest for discovery in particle physics, acknowledging that while scientists hope for unexpected findings, they do not expect to fundamentally upend our understanding of the universe. He recalls the短暂的 excitement around the OPERA experiment's neutrino anomaly and the potential for a similar paradigm shift in the future. Sabina Hossenger emphasizes the need for more critical reflection on scientific methods and theory development in fundamental physics.

The discussion concludes with a reflection on the importance of the conversation and the need for more physicists to engage in such discussions. Sabina Hossenger highlights the evolving nature of the scientific method and the importance of being more careful in theory development. The panelists agree that while new discoveries may not immediately impact daily life, they could have significant long-term consequences and contribute to a deeper understanding of the universe.