I vaguely remember back in my preteen years asking my mother what nature was, but not her reply. I suspect it was similar to the one she gave when I asked why it’s often said time is money. To that, I distinctly recall her answer: ‘You’ll understand some day.’ That was her way of deferring what would have been a complicated explanation of economics with the expectation that I would one day figure it out myself. Unlike my mother, The Big Picture: On the Origins of Life, Meaning and the Universe Itself, by Sean Carroll, does offer an answer to an equally complex question, ‘what is nature?’—a satisfyingly simple and concrete one: a quantum wave function.
As a pop science reader, I have cobbled together a misshapened understanding of quantum mechanics from such books, Quora, Wikipedia; and Lawrence Krauss, Leonard Susskind and Minute Physics videos on YouTube. It was not until I read this book that I had a comprehensive, big-picture view that held together, and that is the value of this read: it so congeals all the factoids and bits of information you already know about science.
It was not until I read this book that I had a comprehensive, big-picture view that held together…
Apart from the easy-to-understand explanation of this view of nature, and the startling though carefully crafted claim that the laws of physics underlying everyday life are completely known, there are other major takeaways in the book that are just as clarifying, benefiting from Caroll’s concise, uncondescending treatment.
Why time exists: Because entropy
There are two reasons why time exists and always marches forward: the universe began to exist, and at low entropy. Entropy is a measure of how much disorder, or randomness, there is in a system. Because of this, things are more likely to develop over time in a certain way than others. That gives us an arrow of time: you remember your past but never your future; a vase can fall upwards but it’s exceedingly unlikely. The physical equations do not prefer any direction of time, but because the universe started in a certain state, that binds us to a certain sequence of events.
To illustrate this limitation, Carroll uses the example of a messy bedroom: there are many more places where your socks shouldn’t be—underneath your bed, atop the bar fridge, on your work desk—than there are areas where they should, precisely one: your socks drawer. So over time your bedroom becomes messy as entropy increases. It could undo its own mess, but that requires a prohibitive amount of energy. So in physical systems in this universe, A tends to cause B, B tends to causes C; and things move from high order to high disorder and not the other way around.
Multiple realisability: A theory within a theory
A remarkable fact of nature is that we can explain many aspects of it using various spheres of vocabularies. The trick is to understand that these spheres overlap only to some extent, not completely, and not to mix up these vocabularies where they don’t overlap. For example, we can use the less granular theory of fluid dynamics to explain to a good approximation the movement of gas in a room. If we wanted to be more precise, we would calculate the individual energies (mass and velocity) of each particle in the room and add them up. So you can talk about the gas in a room using both sets of ideas, the granular one scaling up to the generalised one, though with some loss of information.
Another example is that the structure of the atom can be explained sufficiently (the sufficiency of which explanation depends on what you want to do with the information) using the Bohr model and quantum mechanics. Computers operate on quantum mechanics, but we didn’t need to know quantum mechanics to build computers. There is more than one way to describe a system, which leads us to the next topic.
Ontologies: The many levels of description
Reality is a complex phenomenon and varies depending on what is looking at it. The set of ideas or vocabulary we use to describe certain aspects of reality is called ontology. You can think of yourself as both a human being or a collection of atoms. Both views are correct in their domain of applicability but you can’t mix them up because you’ll end up with absurd results, like this misguided statement: ‘If I’m merely a collection of atoms, why do I have desires and dreams? Do atoms dream?’ SMH
Planets of belief: Beliefs are more comfortable than truth
People have the unfortunate tendency to take as truth what is more comfortable to us, either because we were raised a certain way or because we identify with certain tribes. Steven Pinker, a cognitive scientist and prolific writer on language cognition and how the mind works, asserts that we often believe in particular sets of ideas because we found a home among people who believe the same thing rather than because we independently arrived at those beliefs purely on their merit.
Knowledge, according to this view, is composed of a set of beliefs held together by their mutual consistency. People hold onto views so long as they have coherent propositions. These planets can churn and change, but this is more likely to happen to recently acquired beliefs, not those baked in from a young age. The real problem is, says Carroll, people have multiple sets of beliefs that are internally consistent but can be inconsistent with each other. That’s another way of describing cognitive dissonance.
The case against God: Because it’s not science!
Carroll takes numerous pages to show that the idea of a god is untenable and offends the most basic ideas we confidently know about how the universe works. I skipped most of these pages not because I was offended—I’m agnostic—but because I think attempting to speak about supernatural agents, specifically as they are described in major religious traditions, diminishes the wonder of science and gives too much credit to such ideas. The conversation is already over at ‘Now faith is the substance of things hoped for, the evidence of things not seen’ (Hebrew 11:1). The believer has immediately claimed themselves unreachable through reason, so why waste your time talking physics? Ben Goldacre in his book Bad Science says you can’t reason people out of positions they didn’t reason themselves into.