EVERY age in history has its own ideas about what makes up the universe. “Questions about what kinds of things exist go all the way back to the earliest philosophical texts,” says .
For many ancient peoples, basic elements such as earth, air, wind and fire formed the essence of the cosmos. In the past century or so, we have concluded that matter is built from atoms, that atoms are constructed from a small set of elementary particles, and that those particles are fluctuations in a melee of quantum fields pervading empty space (see “Why is there something rather than nothing“).
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So, job done – reality explained? Not so fast, says Westerhoff. “You need to be absolutely clear about the sense of the word ‘reality’ – otherwise the discussion is going to be all over the place.” For a start, do only physical objects like earth or atoms count towards reality – or things like minds and consciousness, too?
Although the scope of our definition determines the complexity of the puzzle, physics should still supply the solution, says philosopher University. Physics is about just two questions, he says: “what exists?” and “what does it do?”. “If you answer both of those questions, then I think you have answered the question ‘what is reality?’.”
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If so, we’re still a country mile from a resolution. Modern physics supplies answers for only about 4 per cent of material reality – the other 96 per cent exists as mysterious “dark” matter and energy. Essential components of reality such as space and time also remain unexplained (see “Is time an illusion“).
The problems are deep-rooted. Quantum theory is the best description of material reality ever devised, yet we cannot get our heads around what it says. It seems to imply all possible states of a quantum object are equally real until a measurement forces a single state to exist – a bizarre state of affairs pilloried by Austrian physicist Erwin Schrödinger in the 1930s, with his quantum cat that was simultaneously dead and alive until someone looked at it.
The questions that raises are legion. Why is one version of the cat chosen over the other, and what determines which one? What happens to the other version – does it simply cease to exist, or do both persist in parallel versions of reality? The mathematics of quantum theory, while providing a flawless description of the outcomes of measurements, is silent on these crucial questions. And so we hit a brick wall – or do we?
The other possibility is that we are glimpsing something very profound. If the mathematical description is precise but the physical interpretation is messy, might mathematics be the only real thing? In this picture, you can forget matter and energy, whether conventional or dark. The most fundamental things are the 1s and 0s of information, and the universe is nothing but a gigantic data-processing machine. A star, for example, is not a nuclear fusion reactor building successively heavier atomic nuclei, but a computer processing information into more complex forms.
“What we perceive as the physical world is a kind of crystallisation of abstract mathematical structures,” says Westerhoff. Follow this creed, and the ultimate theory of physical reality must come from the mathematical discipline of information theory, with space and time, particles and energy, forces and fields dropping out naturally from this magnum opus.
We then have to ask why our brains construct physical entities from the underlying numerical reality. An answer to that one, and indeed any true understanding of reality’s essence, may require understanding the prism that is consciousness, too (see “What is consciousness“). Until then, we may remain like the prisoners in Plato’s allegory of the cave who, unable to turn their heads to see the objects casting shadows on the cave wall, believe that the shadows themselves are the true reality. Our age’s idea of what makes up the world may be no less flawed than those that came before.
This article appeared in print under the headline “What is reality made of?”
