A couple of months ago my book Cosmological Koans was released. Since I started this book before Max and I started FQXi in 2006, FQXI and the foundational questions community has obviously played a huge role in my thinking and what in the book. So I thought it would be nice to blog about it here and create some conversation. If you've not read it, I (surprise!) strongly recommend it. Limited spoilers to follow ;-)
I would say there are three overall aims of the book:
- Convey a lot of solid physics in a way that is (a) somewhat unusual in approach, (b) "real" in the sense of being conceptually solid such that with effort even someone with pretty limited background can get a real understanding of many core issues, (c) in a way that is tied to vivid stories rather than just text, so as perhaps to make things more immediate and memorable, and (d) in a way that highlights personal experience and at some level philosophical foundations rather than straight-up conventional physics concepts.
- Attempt to convey some of the sense of mystery, wonder, confusion and clarity that studying foundational physics contains. Despite a huge amount physics now describes very well, I wanted to get across in a visceral way that there are still deep and perplexing mysteries.
- Assemble something resembling a world-view that is rigorous in its physics, and in which observers play a key role, by highlighting how -- to varying degrees -- our description of the universe is a co-creation of the universe and the minds describing it.
Along the way, there are a number of science (and other) arguments to be made, including:
- My take on free will, which is that first one should clearly define what it would actually mean to have it (or not), then decide if that is a property of the relevant systems. I, for example, take free will to be the absence of a sense of coercion, an inability, even in principle, to perfectly predict one's decisions/actions, decisions being made for reasons that the decider endorses, and the decisions being unknown without (the decider or another agent) going through the deciding process. I think humans have all of these properties (though that's a long discussion, and not something I'd say I can prove.). Note that this definition does not require any sort of a-corporeal decision-making stuff outside the realm of physics (which there almost certainly is not), nor does it preclude there being influences on our decisions of which we are not consciously aware (which there almost certainly are.)
- Relatedly, my take on determinism. It drives my nuts when people say that the physics governing macroscopic systems (including humans) is deterministic. It's just not. Schrödinger's equation is deterministic, but it maps one current macroscopic configuration to many different future macroscopic configurations -- like any other statistical theory (which may or may not be time-reversible). Whether you consider all of those distinct macro-outcomes to be equally real or only one to be real, the fact is that many of them exist in the evolved state. (And as for the argument that human brains are based on neurons that are essentially classical objects, that's just not right thinking either -- signaling is clearly affected by thermal noise, which is ultimately quantum in nature, so I think it's very clear that one current brain state (or density matrix) corresponds to many distinct future ones, though we don't know what the timescale for that divergence is.)
- My take on entropy and information. I and collaborators have spent a lot of time sorting out what I (now) think is the right way to think about Boltzmann vs. Gibbs entropy, in classical and quantum systems, in and out of equilibrium. Using the same word "entropy" for tho rather distinct concepts, as well as often using it interchangeably with "information" makes a lot of literature on the topic really confusing. But it need not be! I'll write a separate blog about this but for those interested check out this paper, which spells things out fairly clearly (on the entropy side).
- An argument that sorting things into those that are "objective" and "not objective" is too simple and is misleading -- it's a sliding scale. There's essentially nothing, I'd argue, that is totally objective. Even the mathematics we use is based on a set of axioms that we have selected out of many possibilities, and in which we have selected a tiny subset of all possible consequences of these axioms as "mathematics" (even though all are "true"). This selection corresponds to the creation of mathematical information. And admitting that things are not totally objective is OK -- liberating even!
- An anti-reductionist thread pointing out that when we talk about one description being more "fundamental" than another (and don't get me wrong, I'm a big fan of those descriptions!), it's pretty hard to put a finger on exactly what we mean. And relatedly there's almost always a whole lot of stuff (coarse-grainings, boundary conditions, assumptions about the state, indexical information, etc.) that must be added to a "fundamental" description, which undermine any idea that everything is in principle derivable just from the Hamiltonian. It's just not.
And lots more! I had a great time writing and thinking it all through; for those who read it I hope you enjoy it and get provoked in various ways; and to everyone in the FQXi community thanks again for the support and inspiration!