Existential Physics (Hossenfelder 2022)

     Sabine Hossenfelder. Existential Physics (2022) Hossenfelder has made a YouTube reputation as a disturber and explainer. Search for her videos; they’re fun and enlightening. She believes that modern physics is in crisis because it claims more insight and understanding than is warranted by experiment and observation, especially when it comes to dark matter and energy. The theories, the sets of interlocking equations, describe what’s measured, but for consistency’s sake, theorists have added entities that haven’t been observed to interact with the entities that we know about. In her Warning, she says, “Science has limits, and yet humanity has always sought meaning beyond those limits.” Quite so.
     Then Hossenfelder goes on to show how science can inform some of the answers to the questions that exceed the limits of science. Science can clarify and disambiguate some of those questions. For example, do we have free will? The scientific answer (summarised) is: “No, if by free will you mean the ability to choose without being subject to the laws of physics.”

     For choosing is a brain-function, and brains function according the laws of physics. This fact has funked recent philosophers, who see no way out of the answer. But there is one: when we deliberately choose we figure alternatives, and weigh their desirability. We may choose differently than we chose in the past or will choose in the future. We will often choose differently than others choose. Thus, while our choices may not be freely willed, neither are they automatic. We aren’t automatons; we are agents. But we can’t choose without preferring one alternative to the others. Since our preferences are shaped by our genetics and our experience, in that sense, the choice is not “free”. However, we can choose to change our preferences. Odd, that. Is the choice to change our preference free or not? At the neurological level, I think no. At the psychological level, I think yes. And then there's  the spoiler question: How would you distinguish between free and determined choice?
     Hossenfelder does fall into what I think is the common philosophical error of physicists: She believes that physics reveals reality as it really is. Or at least that it is closer to doing so than the messier, less abstract sciences such as chemistry, biology, psychology, and so on. She reminds us that every "emergent property" that biology describes can be explained by chemistry and physics, and that everything that chemistry describes can be explained by physics. Neurology is solving some of the puzzles of psychology by showing how brain function varies with different behaviours, and emotions. Or at least suggesting how to reframe the puzzles.
     In short, she says, no so-called “emergent” phenomenon has (so far) been found to be inexplicable by the lower level from it which supposedly emerged. AFAIK, she’s right. But since the more abstract theories are derived from and explain the less abstract ones, that’s not, I think, a surprise.
     As I see it, physics describes the structure of reality. Einstein’s space-time makes this absolutely clear: What we observe depends on where in space-time we are relative to other entities, and how we are moving relative to other entities. General relativity (GR) describes how one observer’s worldview (measurements) is precisely transformable into another observer’s worldview: a clock runs fast from one POV, runs slow from another, and we can calculate exactly how much the measurements differ. (These calculations are necessary for GPS systems to function.)
     Quantum mechanics (QM) shows that what we observe depends on the event’s context: Electrons behave like particles in some contexts, and like waves in others. Or better, wave equations describe some electron behaviours, and particle equations describe others. None describe electrons. And those equations are the best descriptions we have, so far. There are probably better ones “out there”, and maybe they’ll be discovered. But not in my lifetime, I think. Bummer.

     The fact that GR and QM cannot (at present) be reconciled should not surprise us either, I think. Both are highly abstract descriptions of what’s common and different in our perceptions of reality. Our experience of reality is a simulation created by our brains. We can compare each other’s perceptions, and note whether we perceive the same differences and similarities. That’s the beginning of science, and it’s already at least one level of abstraction away from the simulation which is our experience of the world around us. But that simulation is itself an abstraction, constructed (computed?) by our brains. It’s sufficiently accurate that we can navigate the world, get our food, find our mates, etc. It must be structurally similar to reality, else we could not survive. It may make sense to say that the topology of our experience (the simulation) must be similar enough to the topology of reality to enable our survival. I don’t know enough about topology or brain function to be able to say. I also haven’t a clue how the brain’s simulation becomes what “I” experience. I suspect it’s because “I” is part of the simulation, probably the essential part, but how would one test that notion?
     I enjoyed this book, because (as the above may show) it prompted rethinking many of my ideas. I will read it again. Hossenfelder is an excellent explainer.
     Recommended. ****