Do particles really exist? | Sabine Hossenfelder, Hilary Lawson, Tim Maudlin

Episode Overview

• The episode features a debate on the fundamental nature of reality, specifically questioning whether particles are independent entities or simply excitations of underlying fields.
• Panelists discuss the role of different scientific models (e.g., particle theory, field theory, string theory) and whether any single model can claim to represent the ultimate truth.
• The conversation explores the philosophical implications of physics, touching on concepts like scientific realism, instrumentalism, and the limits of our ability to describe what truly exists.

Key Concepts

• Particles vs. Fields: The central conflict of the discussion is whether particles are fundamental entities or merely vibrations/excitations within a more fundamental field. One view suggests particles are emergent phenomena from fields, while another argues that particles and fields can be postulated as distinct entities.
• Model-Dependent Realism: A key philosophical idea discussed is that our understanding of reality is always mediated through theoretical models. We can't step outside these models to see "what's really there," meaning multiple, different models can be considered equally valid if they accurately describe observations.
• Duality in Physics: The concept that two completely different mathematical formulations or theories can make the exact same predictions for all observable phenomena. This challenges the idea that there is only one "correct" way to describe reality.
• The Role of Evidence: The debate highlights that while multiple models can exist, scientific progress relies on empirical evidence to determine which models are more plausible or better supported. The discovery of quarks through scattering experiments is used as an example.
• Ontology and "Be-ables": The discussion grapples with the ontology of physical theories—what the theories claim actually exists. John Bell's term "be-ables" is used to describe these fundamental entities, which could be particles, fields, or something else entirely.

Quotes

• At 00:00 - "The particle is just a vibration in the field... we don't have to postulate a metaphysical other thing... [Rebuttal] No serious physical theory... says that." - This exchange between Hilary Lawson and Tim Maudlin immediately frames the central debate about the relationship between particles and fields.
• At 01:53 - "It's you can have a certain way of holding the world, and you can apply that, and you can interpret it in that light... But we shouldn't imagine that... there's one version of what's going on out there." - Hilary Lawson explains his post-realist view that science uses different, powerful models to understand the world, rather than converging on a single, final truth.
• At 08:08 - "There are always different ways to look at the same thing. So it doesn't really make sense to say... the particle is the thing that is real, if there is another description that's exactly as good, but doesn't have the particle." - Sabine Hossenfelder uses the concept of duality to argue that if multiple, equally predictive models exist, it becomes problematic to claim that the entities of just one of those models are fundamentally "real."

Takeaways

• Question the reality of scientific concepts. What we call a "particle" may be a useful concept in one successful model but an emergent property in another. Our descriptions of reality are frameworks we apply, not necessarily a direct window into ultimate truth.
• Distinguish between scientific analogy and formal theory. Physicists may use loose language like "particles are vibrations in a field," but a rigorous physical theory has precise definitions. Understanding a theory requires knowing what it formally postulates as existing versus what is simply a helpful metaphor.
• Accept that there may be multiple valid ways to describe the universe. The existence of dualities in physics shows that different, even contradictory-sounding, mathematical structures can accurately predict the same phenomena. This suggests that the quest for a single, ultimate description of reality may be misguided.