The popular view that physics has shown everyday reality to be an illusion is deeply flawed. Understanding how macroscopic phenomena emerge helps dispel this myth, writes Alexander Franklin.
Popular science often tells us that we are radically deceived by the commonplace appearance of everyday objects and that colour and solidity are illusions. For instance, the physicist Sir Arthur Eddington distinguished in 1928 between two tables: the familiar table and the scientific table, while the former is solid and coloured, the scientific table “is nearly all empty space”. Eddington then makes the striking claim that “modern physics has by delicate test and remorseless logic assured me that my second scientific table is the only one which is really there”.1
The idea that everyday objects are not really there is, of course, nonsense! There are few claims of which I am more certain than that the chair on which I’m currently seated is solid and brown.
The contradiction between these two sets of views prompts two questions, which we’ll explore in this article: why do some thinkers claim that we are radically deceived about everyday reality? And, given that they are mistaken, how is it that the nature of the objects that we can see and touch emerges from the very unfamiliar particles that make them up?
Eddington then makes the striking claim that “modern physics has by delicate test and remorseless logic assured me that my second scientific table is the only one which is really there”
The implication of claims like Eddington’s is that familiar objects are in some significant sense illusory, but how could that be? The philosopher Susan Stebbing critiques Eddington by noting that whenever we make the claim that some object is real, we do so in contrast to some illusory object, like an artificial apple: “It is quite sensible to contrast this ingenious fake with a ‘real’ apple, for a ‘real’ apple just is an object that really is an apple and not only seems to be one”.2 Unlike with artificial apples, it is misleading to claim that familiar tables are illusions. One could, sensibly, claim that some specific table has illusory properties – say it was coated in the highly light-absorbing material Vantablack and so its contours were obscured – but it is meaningless to claim that all tables and, worse, that all familiar objects aren’t real.
1 – Illusory properties: wrinkled aluminium foil with a portion – equally wrinkled – coated in Vantablack3
[It is, therefore, an error to claim that we are radically mistaken about the properties of everyday objects. When I claim that my chair is solid, I am surely right, as long as it continues to support my weight and prevent my falling through it. Likewise, in the absence of hallucinations or optical illusions I can be very confident in correctly discerning the colour of the objects around me.
I am opposing the view that the world deceives us as to the true properties of familiar objects and that much of what we think we observe are illusions, that my chair is really neither solid nor brown. Let’s call advocates of this view ‘Illusionists’.
The mistake that the Illusionists make is the assumption that everyday objects have just the same features as their fundamental constituents – so, if their constituents are colourless they infer that the object itself must also be colourless; any apparent colour is then written off as an illusion. This can be called the ‘Lego principle’. The idea is that physical objects, like objects made of Lego bricks, are such that if you take them apart they are just like their constituents. So, the pieces that make up a Lego dinosaur will be hard and colourful with various different small circular knobs on horizontal surfaces and smooth vertical surfaces. And, while the dinosaur will have a different shape from its components, it will inherit their colour and hardness.
I am opposing the view that the world deceives us as to the true properties of familiar objects and that much of what we think we observe are illusions
Illusionists assume the Lego principle applies to more than just Lego: they think that everyday objects should have similar properties to their parts. Eddington should be considered an Illusionist in this sense. The atomic theory of matter tells us that atoms are nearly all empty space – the nucleus is as tiny relative to the atom as a fly is to a cathedral. On that basis, Eddington supposed that his table is also “nearly all empty space”. Likewise, he would suggest that, since my chair is made up of lots of parts that lack solidity and colour, the chair itself cannot possibly be solid and brown.
The best response to the Illusionists is to deny the Lego principle and accept that the relation between the properties and features of fundamental particles and those of everyday objects is far more subtle and complex. The brownness and solidity of my chair are not illusory, they are real. To say otherwise is an abuse of language: to give another example in support of Stebbing’s point – if I were to claim that my chair is nearly all empty space, this would suggest that it is hollow, or has the structure of Swiss cheese. However, my chair is solid, and the fact that its atoms are, in some sense, rather empty, does not undermine its solidity! The right question is: how do these features of the chair emerge out of the underlying non-brownness and non-solidity of the particles that make up the chair? That question is addressed by the Emergentists.
In contrast to the Illusionists, Emergentists accept that my chair really is brown and solid. They then have a much more difficult challenge: how do everyday objects gain such features while these are lacked by their constituent parts?
Let’s think about how my chair holds me up and consider a small part of the complex array of processes, features, and mechanisms responsible for that. Like many scientific inquiries, there are many ways to proceed. One way to go is to think about how the chair is held together – so, if my chair is made of wood, we would need to think about the screws that connect the pieces and the fibres that underlie the structural integrity of each piece. A wonderful aspect of this kind of investigation is that it prompts a long chain of further questions concerning how each sub-part of each part of my chair is held together. What this demonstrates is that the subject matter of all the sciences is beautifully interconnected. A question as seemingly straightforward as one about how my chair holds me up can, with the right degree of perseverance, take us from an inquiry into the organic processes that make wood so robust, down to the strong nuclear force which holds the quarks together in the atomic nucleus!
To consider just one link in this chain, we could focus on the structure of the atom. In order for my chair to hold me up, the atoms that comprise the chair have to take up space and prevent some other particles from sharing that space. While it used to be thought that the electrons orbit the atomic nucleus much like planets orbit the sun, there are aspects of this picture which are misleading. In particular, something like the Lego principle seems to be involved in the idea that the very small – the atom – so closely resembles the very large – the solar system.
What that picture gets wrong is the idea that electrons have determinate positions that are changing as they ‘go round’ the nucleus. In fact, that wrong idea makes it seem utterly mysterious how atoms take up space – if electrons were just particles in orbit then it would be very surprising that many other electrons couldn’t overlap those orbits.
However, according to the mainstream interpretations of Quantum Mechanics, there are no facts about where any electron is located at any time. Electrons should rather be thought of as spread out and occupying the entire path of the orbit at once – as such, electrons occupy a shell around the nucleus. To get from the existence of electron shells to the stability of matter, one further ingredient is the Pauli exclusion principle – a law that prohibits any two electrons (or other fermions) with exactly the same properties from being in the same location as one another. Together with the fact that only certain orbits are allowed by the theory, the Pauli exclusion principle prevents outer electrons from ‘falling in’ to the orbits of inner electrons. Thus, atoms take up space by forcing electrons into orbiting shells of increasing size and limiting the number of electrons that can share those shells. This, then, is part of what allows the atom to take up space, and, after many more steps, to my chair keeping me aloft! This is, of course, just one small part of the total story, but it gives us an idea as to the complexity and subtlety involved in the emergence of everyday features like solidity.
What this demonstrates is that the subject matter of all the sciences is beautifully inter-connected
I have argued that we should not be Illusionists – that is, we should accept that the features we normally take everyday objects to possess are, in fact, possessed by such objects. We should rather be Emergentists who contemplate the tremendous complexity involved in joining together the myriad parts of everyday objects to generate their observed features.
The story of how we get to solidity helps undermine the Lego principle: once we understand how features of everyday objects can come out of components that are so different, we should no longer be attracted to the thought that objects are similar to their parts. But why is Illusionism so attractive in the first place? While I don’t think that we are radically deceived about the features of everyday objects, I think we are often deceived by the simplicity of our familiar world into thinking that its parts and processes are likewise simple. One of the most interesting projects involved in the study of emergence is to explain what gives rise to the relative simplicity of everyday objects. The answer to this is the cooperation of parts.
A nice analogy comes from picturing a crowd executing a Mexican wave (or stadium wave): when they are coordinated in their actions, the description of what’s going on is very simple, one can simply identify the position of the peak of the wave. However, where coordination fails, it becomes much more complex and no simple description of the crowd is possible. Like a Mexican wave in a crowd, the simplicity and the stable patterns we observe in everyday objects are the result of a huge number of interactions between individual elements or components. We are terribly lucky to live in a world where such interactions characteristically result in coordination, for in the absence of such coordination we would have no stable structures and no entities like ourselves!
Returning to the question we started with, we are not radically deceived about the nature of everyday objects so long as we avoid the Lego principle. On the other hand, those who endorse the Lego principle are radically deceived, and the emergent simplicity of the world around us makes such a principle rather beguiling.
 Eddington, Arthur Stanley. “The Nature of the Physical World” (1928). Dent.
 Stebbing, Susan L. “Philosophy and the Physicists” (1937). Methuen. https://en.wikipedia.org/wiki/Vantablack#/media/File:Vantablack_01.JPG]
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