Do Protons Exist?
by David Geelan | 27 January 2021 |
The question in the title might seem like a strange one. Most people (at least among those who know about those positive particles in the nuclei of atoms) are likely to take it for granted that they are real.
No one has ever seen a proton, though. They are far too small for us to be able to see with our eyes, and we can’t even see them directly with electron microscopes. Protons are 100 million times or so smaller than the wavelength of light, and even 1,000 or so times smaller than the wavelength of an electron microscope.
We must infer their properties—mass, charge, spin, notional size and so on—from indirect measurements.
In the philosophy of science there are realists who argue that we have enough evidence to be able to state that there are actual, physical entities that explain the readings we get in these measurements: that protons exist.
Realists and idealists
There are also idealists who consider that, while they are happy to stipulate protons as theoretical, conceptual entities, we do not have enough evidence to confidently claim that this means there actually exist entities of this kind.
These technical meanings of the terms realist and idealist within the philosophy of science shouldn’t be confused with their more usual meanings in conversation or politics, where a realist is someone who responds to the realities and features of a situation, while an idealist is someone who always seeks the perfect ideal. In philosophy of science, realism is the notion that the entities in science—protons, electrons, quarks, bosons and so on—are real things in the universe, while ‘idealism’ suggests that they are more like conceptual entities about which we can’t definitively say that they exist, but which are useful shorthand names for sets of properties that are useful to us.
The example of protons is slightly more complicated, because things at the quantum level are philosophically complicated anyway: they behave in ways that are not particularly intuitive to us based on our experiences of the world around us. That quantum uncertainty doesn’t explain the point I’m making here, though.
Let’s take a different example at a more accessible scale (or, if it’s inaccessible, in a different direction): is Earth’s inner core solid?
Our best current science says it is—but that the outer core is liquid. But we’ve never been there to see, can never conceivably go there to see, have no way to check directly. We must infer its state from patterns of seismic waves moving through the planet, as we detect them at a web of surface detector stations.
So it’s not about the domain of quantum handwaviness; it’s about things we’re confident we know in science that we do not know through direct observation.
What can we know?
While the validity of inferences in science arises often in discussions around creationism, that’s not the direction I want to take it this time. Rather, the question is about whether we have direct, unmediated access to reality, or whether all our experiences of the world are in some way filtered.
It’s not only these examples that involve indirect inference that I’m thinking of. Current science shows that our actual visual field—the area of vision where we can see clearly and in detail—is a relatively small circle at the centre of our apparent visual field, and that our brain is filling in most of the rest of what we think we’re seeing in any moment from memory, imagination, scanning beyond that small field and from much-less-precise peripheral vision which picks up motion but not a lot of detail. The very way in which we look at and observe the natural world visually is largely illusory, in that what we believe we are seeing is not the direct, raw data being generated by our eyes.
We are subject to optical illusions, and also to other kinds of illusions. If you’ve spent a lot of time on the web in the past few years you might know about the photo of a dress that some people swear is coloured in white and gold stripes and others swear just as strongly is black and blue. In an example from a different sense, there is an audio recording that some people swear is of a man saying “Yanni” and others swear is “Laurel”.
Our senses are relatively reliable (assuming we don’t have a disability) or life would be very difficult indeed. But they are not perfectly reliable. We have probably all seen mirages, and static images that are apparently moving because of the way our eyes interpret them. Many sightings of UFOs, for example, are explained by various kinds of optical illusions.
It’s worth noting that about 1 in 12 human males of Northern European descent are colour-blind, and experience the world differently from the rest of us. But it’s also arguable that our senses mean we all experience the world somewhat differently from each other. If my senses are not aided by my glasses my visual field is very impoverished, and I couldn’t safely ride my motorcycle, drive, or work on a computer without putting my face a hands-breadth from the screen.
Beyond our physical senses, we always interpret the world through our existing knowledge, understandings and concepts. Indeed, Einstein said, “It is the theory which decides what we can observe.”
Raw data
The world is too complex for us to access “raw,” as sense data. You might have seen a baby stare in absolute fascination at something apparently banal like the texture of a piece of fabric. Their developing minds are forming concepts, and the world will be much easier to manage once the fabric is subsumed into the larger concept of “shirt” and then largely ignored (unless the shirt is especially hideous or resplendent).
The concept of “dog” is what enables us to distinguish between the four-footed furry mammals that fit into that group and those that fit into the concepts of “cow”, “cat,” and so on. Our concepts order and structure the world for us.
Language is important, too. While it’s not universally accepted, the Sapir-Whorf hypothesis suggests that people who speak different languages experience the world differently, because of the ways in which the conventions of their language change how they conceptualise the world. For example, English is not a gendered language, but in Spanish and Italian inanimate objects such as cars and tables have a gender associated with them. Does that mean speakers of those languages experience inanimate objects in slightly less impersonal ways, or with some other differences?
Returning to the notions of realism and idealism, and the nature of reality, these shortcomings of our senses should, I think, lead to some modesty about the claims we make about the physical world around us. Our access is mediated both by our senses and by our concepts. Our scientific theories are the best explanations we have been able to construct, but are not certain or eternal: they are always subject to revision based on new evidence or better experiments.
Modest God claims
I would argue that these considerations should also lead to some modesty and humility in the claims we make about God. There are (at least) three dimensions to this:
- The shortcomings of our senses and our ways of making sense of the world apply to our reading and interpretation of Scripture, as attested by the very wide range of interpretations and long-running controversies about the meaning of almost any text you can name. There is no simple, direct translation from text to concept, and to some extent the theory decides what we can observe.
- The same issues also applied to the Bible authors: they captured the things of God in language to the best of their ability and understanding, inspired (but I think most would agree, not verbally in the form of word-for-word dictation) but with human shortcomings, so their access to the Divine was mediated—and that is reflected in the text.
- God is infinite, while we are finite. I’ve alluded before to the story of the blind men and the elephant, where each is touching a different part of the animal, unable to see the whole picture, and perceives the elephant as a wall, a rope, a fan, a hose, a tree trunk. Our knowledge of God is necessarily partial, and that of the Bible writers similarly so. In the case of this analogy, the “elephant in the room”(immanent and transcendent) is literally infinite. Any fractional knowledge of something infinite, no matter how large, is essentially a fraction divided by infinity, which mathematically is zero. Our knowledge is always so small compared with the scale of its Object that humility is the only possible response.
Neither in science nor in theology nor in our personal search for meaning and the best way to live should these considerations lead to a “philosophy of despair” or to deciding that we can never know, will never know, may as well give up. Rather, in all those activities, it’s incredibly exciting that there’s more to learn, so much more. And there always will be more to learn, because the Subject and Object is inexhaustible.
At the risk of belabouring my usual theme, I’ll close by noting that it wouldn’t make sense to come to blows or lose friends over whether the dress was black/blue or white/gold, or whether the man said “Yanni” or “Laurel”. The nature of the world around us and the nature of God are much more consequential matters, of course, but humility about our own understanding and respect for what we can learn from the knowledge and experience of others can only serve us well.
David Geelan is Sue’s husband and Cassie and Alexandra’s dad. He started out at Avondale College and has ended up (so far) as an Associate Professor of Science Education at Griffith University on the Gold Coast, Australia.
