Multi-level emergence

"Emergence" is a term for the way a large system with simple rules can give rise to more complex behaviour. Our universe has multiple levels of emergence:

• We start with the fact that space-time is full of fields. The Higgs field is a scalar, meaning that it is just a number that varies smoothly between points. Other fields are more complex things.
• From the fields emerge particles: photons, electrons, quarks and more.
• From the particles emerge a useful collection of atoms.
• From the atoms emerge a dizzying set of molecules,
• From some of the atoms, life emerges.
• From some of the life, intelligent cooperating lifeforms emerge.
• Also the gravitational field is just right to create stars and planets and other stuff out of the atoms.
• And nuclear interactions in stars, and when stars explode, is just right to create all those useful atoms.

The scientific solution to this fortuitous situation is backward causation. We're here, so the universe has to be complex enough to create us. We think therefore there has to be a route to thinking.

But this is, however, very unsatisfactory. There are multiple ways that we can go outside of science to guess a solution that doesn't involve backward causation. The traditional one is to postulate a designer, but that breaks Ockham's razor by trying to solve the unlikely complexity by postulating something even harder to explain.

We know our Universe does spontaneous symmetry breaking. The easy way to understand that is to imagine a pencil perfectly balanced on its point. This is an unstable position. The slightest movement of air will make it fall to a stable position on its side, but we can't predict which direction. Another example is that when a liquid gets cold enough it has a lower energy state as a solid, but the order in which molecules join the solid, and hence the shape of the solid, is unpredictable. An example of this in the creation of the Universe is that the Weak Force and Electromagnetism were initially, at high energy, united as one, but they split in a symmetry breaking way.

So my non-science explanation for our amazing multi-level emergent universe is that there are a very large number of universes which are not in causal contact with ours, and hence not amenable to scientific study. Each universe has properties that we can imagine arise in an unpredictable way, like the direction of our falling pencil. Universes with no emergent properties are much more common than those with one level. Universes with one level of emergence are much more common than those with two levels, and so on. And then, there is our unimaginably unlikely and interesting universe. All those universes with less levels of emergence don't have anyone to notice how boring they are.

Which brings us to the title of John Barron's book. We are "The Universe that Discovered Itself".