Growing up in the US during the oil embargo of the early 1970s, I was bombarded by public service announcements encouraging people to conserve energy. But at a very young age, I also read that “energy is always conserved”, according to physics. This baffled me. If nature automatically conserves energy, why would human efforts to do so be needed?
I soon realised that physicists don’t exactly speak English. They employ a dialect full of familiar-sounding terms with unfamiliar meanings (including “conserve” and “energy”). Worse still, many words, including simple ones like “force” and “mass”, don’t even signify what physicists originally intended. Consequently, the language we use to talk about physics obscures some of our most beautiful and fascinating discoveries about how the universe works.
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Some scientists might shrug and say it is neither surprising nor problematic that the words aren’t completely clear. After all, the foundations of physics are experiment and mathematics. Those are what matter; words are inevitably mere shadows.
Though I agree that data and equations are paramount, physicists convey their ideas, both to each other and to non-scientists, using language. When their wording is ambiguous or opaque, essential lessons about the cosmos may be misunderstood.
So let’s look closer at the language of physics, and how three seemingly simple words have morphed over time, becoming snares for the unwary. Such deceptive terms and metaphors are widespread in physicists’ dialect. In pausing to contemplate them, we can gain a clearer, deeper and more satisfying vision of reality.
To set the stage, let me begin with another short story from my youth. When I was 20, I paused my physics studies for a year to pursue music at the Paris Conservatory, taking classes in piano and composition. During my first days in the city of lights, I felt constant stress as I struggled to communicate in French. Attending a classical concert, I found it a challenge to buy a ticket, speak with the usher and decipher the programme. But when the musicians began to play, I felt a sudden rush of unanticipated relief. I had somehow forgotten that the music itself would require no translation – it would soothe my brain and heart just as it did at home.
Like music, mathematics can sometimes transcend language: the set of symbols 2 + 2 = 4 can be wordlessly interpreted across many cultures. Since theoretical physics is the most firmly maths-based science, perhaps it inherits this linguistic independence. Must E = mc2 really be translated into words?
The answer is certainly yes. E and m stand for “energy” and “mass”, but what do these words really mean? No understanding of Albert Einstein’s famous formula can be attained, even by physics students, without a discussion of the precise connotations of these terms. This is no small thing, because in modern physics there are multiple types of energy and mass, each with an unfamiliar definition. Unless one chooses the correct types, E = mc2 isn’t even true. In short, “energy” and “mass” aren’t shadows, they are load-bearing supports.
All about atoms
With this in mind, let’s dive in to the first of the three words that I want to explore in more detail. I find the history of the word “atom” particularly illustrative. Its origin is traced to the ancient Greek philosopher Leucippus and his student Democritus, who suggested that material objects are made of tiny, elementary, indestructible particles. The particles of each type were imagined to be identical and indivisible, hence the name “atom”, from the ancient Greek atomos, meaning “uncuttable”.
Much later, as the 19th century dawned, chemistry experiments provided evidence that all materials are indeed made from elementary substances – hydrogen, oxygen, carbon and other elements – and that each such substance consists of identical, minuscule objects. European scientists of the time were familiar with ancient Greek philosophers, so it was natural for chemists such as John Dalton to call these objects “atoms”. After some initial definitional chaos, the meaning of atom was settled by the middle of that century, referring as it does today to the fundamental unit of a chemical element.
Yet the word is a misnomer. Soon after electrons were discovered at the turn of the 20th century, it was understood that they inhabit the outskirts of atoms and can be stripped off and reassigned to other atoms in chemical reactions. Their negative electric charge is cancelled, within each atom, by a positively charged nucleus, itself also divisible. So much for atoms being uncuttable.
But, by then, the word “atom” had already been established. Decades of research papers and conversation had relied on the term; replacing it would be no easy matter, practically or psychologically. That is why, despite knowing atoms were divisible, scientists retained “atom” and shifted its definition. Language has staying power.
Where language gets tricky
Fortunately, the fact that atoms contradict their own name is harmless, albeit amusing, because the word “atom” no longer carries the resonance it had – unless you happen to have studied ancient Greek. But other expressions in physics pose greater difficulties.
Take the word “force”, widely used in ordinary English, both as a verb (“I forced the door open”) and as a noun (“lifting the box required great force”). The word took on a precise scientific meaning in the late 17th century, as Isaac Newton was developing his laws of motion. He used the term to mean the amount and direction by which one object pushes or pulls on a second object, thereby affecting the latter’s motion. (Often writing in Latin, Newton used the word “vis”, but translated it as “force” when writing in English.) For two centuries, the meaning of “force” in physics dialect was clear because this definition conveniently overlaps with the standard, intuitive English meaning.
But trouble was brewing. Scientists learned in the 19th century that the pull of static electricity arises from something they called the electric field. A corresponding magnetic field is responsible for the pull that holds a magnet to a metal object. Soon, though, other roles for these fields, having nothing to do with pushes or pulls, were discovered. Most importantly, waves in these fields manifest as what we call light. The two fields are also at play in the emission and absorption of light by atoms and in a variety of other exotic effects.
Physicists needed a name for the entire category of these “electromagnetic” phenomena, including not only the pushes and pulls, but also light and its interactions with matter. They had a choice: either define a new term that encompasses all these processes, leaving “electromagnetic force” to mean only the pushes and pulls, or expand the definition of the older term to include them all. Regrettably, they chose both.
When talking among themselves about electromagnetic effects, physicists often use “interaction”, as in: “lasers, firelight, chemistry and collisions of electrons are all caused by the electromagnetic interaction”. To my mind, this word is particularly apt, and it is unfortunate that it isn’t used more widely. The meaning of “interaction” in physics is close to its meaning in English, where it represents the idea of interplay or contact between people or objects that can cause a change in their behaviour.
But scientists also just use the word “force” in place of “interaction”, portraying the electromagnetic force as responsible for all electromagnetic processes. This is problematic because it extends “force” far beyond our intuitive understanding of the word. For instance, they use the word to refer to four “fundamental forces”: electromagnetism, gravity and the strong and weak nuclear forces. In doing so, they lump gravity’s pull together with the ripples in space and time known as gravitational waves, describing them all as “due to the gravitational force”.
The true meaning of “force”
Physicists also sometimes say things like “the weak nuclear force powers the sun and supernovae, and causes certain atomic nuclei to decay”. But this can easily be interpreted to mean that these important effects occur through a push or pull, whereas they actually involve something far more remarkable than a traditional force: the transformation of a particle from one type to another.
Admittedly, the problems with “force” only go so far. It doesn’t take long to highlight the two different meanings, as I have done here. The word “particle“, however, takes these issues to a higher level.
Like “force”, “particle” has multiple definitions in physics dialect. In one, it retains its original meaning from standard English. But it has another meaning that partially conflicts with the one we are used to. This can cause serious misunderstandings, sometimes even for scientists.
Must E = mc2 really be translated into words? The answer is certainly yes
In ordinary English, a quintessential particle would be something like a grain of sand. It is a simple thing; it looks like a small dot. If thrown, it moves along a narrow path. If placed in a box, it will just sit there, doing nothing. Hearing that an electron is an elementary “particle”, we naturally imagine it to be an even smaller dot, perhaps infinitely small, to the point of indivisibility. Our intuition for “particle” then provides us with an idea of how an electron should behave. We imagine a moving electron as a dot traveling on a narrow path. If the electron is placed in a box, whether that box be large or small, we envision the electron sitting within it, stationary, inactive.
This is indeed how scientists conceived of electrons for decades after their discovery. But we now know they aren’t like this at all. Unlike a grain of sand, an electron is a tiny wave. Though its wavy nature reveals itself in many ways, let me mention just two. First, an electron in a box, rather than lying still and doing nothing, instead vibrates billions of trillions of times a second. This is wavelike behaviour: the “standing waves” formed on a plucked guitar string are familiar examples of waves that naturally vibrate and yet go nowhere. Second, waves spread out in a way that particles can’t, making them sensitive to their container. An electron responds to its enclosure’s shape and size. For instance, if a box with an electron inside it shrinks, the electron’s energy increases.
Yet electrons aren’t ordinary waves, either, because they are indivisible, unlike sound or water waves. For this reason, some physicists, going back to the 1920s, have entertained the use of the word “wavicle”, which captures the idea of a minimal, indivisible unit of a wave. I personally like the term because it comes with no baggage, no pre-existing meaning in English that could confuse the hearer. Its novelty frees the mind to imagine a new concept that is neither particle nor wave. Unfortunately, the word “particle” is embedded as deeply in the language of physics as “atom” was at the turn of the 20th century, and trying to replace it with “wavicle” would probably be an unwinnable battle.
‘Particles’ aren’t really particles at all
Yet the fact that particles are nothing like specks of dust is among our most foundational discoveries. We cannot let this crucial lesson be obscured by our choice of words. If the words can’t be changed, we have to learn to see beyond them, to cultivate an appreciation for “elementary particles” that exceeds our intuition, and open our minds to what the word actually denotes in modern physics.
In highlighting the challenges of interpreting scientific language, I speak from first-hand experience. As a teenager, I read many books and articles about physics, and I tried to take their words at face value. I did the same when my first physics teachers used expressions that sounded familiar. But in an inverted image of my Parisian experience with music, here I found myself unable to interpret what seemed to be spoken in English. I blamed myself, at the time. It was only when I took advanced physics classes and began to build my understanding on the maths underlying the ideas that I learned the physics concepts properly. Then it became clear that unfamiliar meanings had been the problem all along.
Some physicists entertain the word 'wavicle' instead of 'particle'
Today, as a professional physicist, I find that scientific language poses a more subtle challenge. Despite the argument that science is mainly founded on wordless notions – empirical data, equations, thought experiments and an inspired intuition for the material world – the doing of science requires scientists to communicate. We must share new ideas and hypotheses so that they may be discussed, weighed and evaluated. As we do so, the language we use can affect our imaginations. When we hear a familiar word, our brains instantly import its conceptual baggage from standard English, packed with its connotations, associated metaphors and visual images. If it has been substantially redefined by physicists, as is the case for “particle”, this baggage can be misleading, even to the point of derailing our efforts to grasp core aspects of the cosmos.
Despite my decades of experience as a particle physicist, and knowing in my heart that electrons, quarks and Higgs bosons are quite unlike grains of sand, I can’t prevent my mind, upon hearing the word “particle”, from promptly conjuring up an image of a tiny dot. It seems inescapable: even for experts, language affects our wordless imaginations so deeply that it can’t fail to influence the way we think. Since this influence potentially interferes with our conception of nature, it is essential for us to be aware of it and to compensate for it.
Can we dream of a day when all the problems of physics dialect are resolved? Sadly, there seems little chance of this. The stories of “atom”, “force” and “particle” suggest that linguistic hazards are unavoidable. As we have seen, terms that initially seem appropriate become entrenched long before they prove inadequate or misleading, by which point they are almost impossible to dislodge. Our best bet, it seems, is to appreciate the dialect’s limitations and find ways to circumvent them. Only then can we clearly perceive the mysteries and majesty of our universe.
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