In this blog post, I’ll explore the evolution of the various atomic models humanity has devised to understand the nature of the atom, the essence of the atom revealed in that process, and the new perspective this offers on the world we live in.
A long time ago, by human standards, the British chemist John Dalton gave me the name “atom.” Of course, the ancient Greek philosophers also called me that. However, Dalton added a modern meaning to that name: “the unit that can no longer be divided.” I do not know why he singled me out and gave me that name, but in any case, from that point on, I began to attract people’s attention. Physicists, in particular, were deeply curious about my true form. Just as devout believers imagine the face of the Creator, some devoted their entire lives to painting my portrait. This essay is the history of the past game of hide-and-seek between my portraitists and me, as well as a record of the failed portraits.
Dalton believed I was the smallest, indivisible unit. However, long ago, the British physicist J. J. Thomson (Joseph John Thomson) had a different idea. While observing a phenomenon in which something emanating from the negative terminal flowed toward the positive terminal when a voltage was applied to a vacuum tube, Thomson discovered that this unknown stream—or particle—was an “electron.” He argued that this electron constituted a part of me, and thus the “Thomson model,” or “raisin pudding model,” was born. Since Thomson had discovered the electron, I was no longer a particle composed of the smallest units. Meanwhile, looking at the portrait he painted, electrons are embedded all over my body, just like raisins in pudding. From my perspective, it was a bit disappointing, but compared to other painters of his time, it was clearly a magnificent work.
Shortly thereafter, I heard the news that another British physicist, Ernest Rutherford, had completed my portrait. The experiment he conducted was simple: he bombarded a thin gold foil with alpha particles and observed whether the particles passed through the foil, were deflected, or bounced off. Alpha particles—which sometimes make up part of me—are particles much smaller than I am and carry a positive charge. If electrons were embedded in my body like raisins, as in the portrait Thomson had painted earlier, no alpha particles should have been scattered off the gold foil. This is because alpha particles are smaller than me, so unless they collide with the electrons embedded like raisins, they would pass straight through the gold foil; and even if they did collide with an electron, since the electron carries a negative charge and the alpha particle a positive one, they would attract each other and the particle would be deflected only very slightly. However, Rutherford’s observations were unexpected. Several alpha particles were found at positions where they had been deflected from the gold foil as if they had been greatly deflected or nearly reflected. To explain this result, there had to be a positively charged particle of large mass capable of repelling the alpha particles and causing them to bounce off. Therefore, Rutherford concluded that positively charged particles were clustered right in the center of my body, and he named this structure the “atomic nucleus.” And so he completed his new portrait, the “Rutherford Model.” If you look at the illustration, you’ll see an atomic nucleus in the center, with tiny electrons orbiting around it. Compared to the raisin model, this was a new masterpiece, but I still felt something was missing.
Rutherford’s illustration received high praise from many. It became so famous that even today, most people still picture me exactly as depicted in the “Rutherford model.” However, compared to Rutherford’s work, the model I’d like to praise is the “Bohr model,” which was completed shortly thereafter. Danish physicist Niels Bohr observed a phenomenon in which light is emitted when hydrogen gas is discharged, causing hydrogen molecules (H₂) to split into two hydrogen atoms (H). He hypothesized that energy is released in the form of light when electrons move to different orbits, and he also discovered that the spectrum of that light corresponds to specific energy values. Combining this assumption with his findings, he made some modifications to Rutherford’s diagram. While Rutherford had merely stated that electrons orbited the atomic nucleus without detailing their orbits, Bohr redrew the diagram, clearly indicating that the electrons’ orbits were discrete and distinct from one another. In other words, the “Bohr model” explained the phenomenon whereby the energy emitted when electrons move between different orbits is fixed at specific values by pre-defining the electrons’ orbits in the diagram. Although his drawing is not as widely known as Rutherford’s portrait, it has served as a fine example for later artists and for artists today.
The “Bohr Model,” which gained popularity through word of mouth among painters, also had a profound impact on young artists. Shortly thereafter, several painters, including the German physicist Werner Heisenberg, emerged with a new artistic style known as “quantum mechanics.” While acknowledging the value of the “Bohr Model,” they pointed out its limitations. The reason was that it could not adequately explain the spectra emitted by atoms other than hydrogen. Painters of the quantum mechanics school argued that portraits must be painted in a different way than before. Their claim was revolutionary: “It is impossible to paint an accurate portrait.” According to quantum mechanics, all particles—including electrons—exhibit properties of both particles and waves. And since these properties are expressed as wave functions, we cannot know both the exact position and momentum at the same time. In short, since there is no way to know exactly where an electron is or how fast it is moving, the electron’s orbit as depicted by Bohr cannot be drawn either. Neither the electron’s orbit nor the position of the atomic nucleus can be known with certainty; all that remains is probability. The “modern atomic model”—this new portrait drawn in this way—was an illustration visualizing the probability of the particles that make me up.
Decades of effort to paint my portrait ultimately came to a close, leaving behind this enigmatic image as my final legacy. At first, humanity expected me to be the origin of all things, the fundamental unit of the universe. However, far from being the alpha and omega, even a modicum of certainty and predictability crumbled in my final portrait. It’s no wonder they were so disappointed.
I, the “atom,” am composed of countless particles, and these particles exist by interacting with other particles around them. Therefore, while it is true that these tiny particles actually exist, they cannot be precisely captured and depicted. This is because everything is constantly influencing everything else. But isn’t this true not only of atoms but also of human beings? Every person lives within a chain of relationships where we constantly influence one another. And why limit this to just people? Every living being exchanges influences with other living beings, its surrounding environment, and the objects around it. Therefore, what the history of my portraits may be telling us is that we all live as “open systems.”
