In this blog post, we explore the nature of the universe, focusing on the Copenhagen interpretation and the many-worlds interpretation—two of the most prominent interpretations of quantum mechanics.
Quantum mechanics, along with the theory of relativity, is a crucial theory that has significantly shifted the paradigm of modern science. It shattered our firm belief in Newton’s classical mechanics, which had seemed unshakable, and has been widely applied not only in theory but also in practical fields, exerting a profound influence on technological advancements in our daily lives. For example, quantum mechanical theories form the core of modern electronic devices and semiconductor technology, enabling the development of equipment such as smartphones, computers, and GPS. However, despite these everyday applications, quantum mechanics remains a subject of diverse interpretations due to its complexity, which runs counter to human intuition. Since there are still unexplained areas, new theories continue to emerge.
To understand the complexity of quantum mechanics and the reasons behind its various interpretations, we must first examine the significance of “interpreting mathematical formulas” in physics. In physics, mathematics is used as the language to describe phenomena or problems because mathematical formulas are logically consistent and free of contradictions. While the mathematical processes involving equations and functions appear perfect in themselves, the question of how to interpret them in the real world we live in sparks debate on an entirely different level. Taking the “Schrödinger equation,” a representative equation of quantum mechanics, as an example, the results obtained from this equation are expressed as a “wave function” that describes the state and energy of matter; however, depending on how one interprets the results of this function, vastly different interpretations emerge.
One of the most prominent interpretations of quantum mechanics is the Copenhagen interpretation. Proposed by scholars such as Bohr, Heisenberg, Born, and Dirac, this interpretation encompasses the Schrödinger equation, the wave function, and the principle of uncertainty, and is based on probabilistic thinking. In other words, it explains that the position and state of a quantum particle are not fixed but are distributed probabilistically across a broad region. Consequently, unlike the certainty commonly experienced in everyday life, quantum mechanics employs a “probabilistic model” to predict the outcome of events. In other words, we can only state the probability that a particle exists at a specific location, and its position is only clearly determined when the process of observation intervenes. This explanation marked a major turning point in the interpretation of physical phenomena and provided a highly useful framework for predicting various experimental results.
Next, the Many-Worlds Interpretation is another fascinating interpretation of quantum mechanics. While the Copenhagen Interpretation explains the occurrence of probabilistic events within a single world, the Many-Worlds Interpretation posits that all possible events actually occur in their respective worlds. For example, when playing rock-paper-scissors with a friend, if there is a world where I lose, there is simultaneously a world where I win. The Many-Worlds Interpretation has become widely known to the general public through the concept of parallel universes and is a theory frequently featured in science fiction novels and films. Although the idea that worlds branch off into multiple paths through the concept of quantum decoherence is difficult to verify experimentally, it has offered its own explanation for the counterintuitive nature of quantum mechanics.
Finally, the hidden variable theory argues that the uncertainty observed in quantum mechanics is actually due to “hidden variables” that we do not know. In other words, this perspective holds that the uncertainty in quantum mechanics stems simply from our failure to fully understand all the variables of a phenomenon, and that all phenomena are, in fact, perfectly predictable. Albert Einstein supported this theory with his famous quote, “God does not play dice.” However, confidence in this theory declined significantly when Bell’s inequality experiments in the 1960s failed to verify the results predicted by the hidden variable theory. Nevertheless, this interpretation is regarded as a meaningful attempt to challenge the complete explanation of quantum mechanics.
Although various interpretations of quantum mechanics have emerged, research grounded in empirical verifiability remains essential from a physical perspective. Since scientific progress stems from verification through experiments and observations, verifiable interpretations hold a more significant position. In fact, the experimental success of quantum mechanics has explained numerous phenomena that could not be accounted for by classical physics and has laid a crucial foundation for applications across various industrial sectors. The Copenhagen interpretation is relatively highly regarded in light of these empirical achievements. For example, it explained why electrons maintain specific orbits through the hydrogen atom orbital problem, and it demonstrated the existence of particles capable of crossing energy barriers—a phenomenon classical physics could not explain—through the tunneling effect.
The impact of quantum mechanical interpretations on philosophy and other disciplines cannot be overlooked. The Many-Worlds Interpretation sparked philosophical discourse on topics such as parallel universes and influenced various theoretical studies, including string theory, thereby providing an opportunity to promote the convergent development of mathematics and science. Philosophers, too, began to deeply contemplate the meaning and essence of quantum mechanics, which further enriched discussions on epistemology and ontology. Interpretations of quantum mechanics have crossed philosophical and scientific boundaries, playing a role in promoting mutual development.
Quantum mechanics still contains many unsolved problems and various interpretations. While the Copenhagen interpretation, the mainstream theory, demonstrates strengths in empirical terms, the Many-Worlds Interpretation and hidden variable theories are still being studied by many scientists and philosophers. We hope that further experiments and theoretical examinations will shed more light on the mysteries of quantum mechanics. Ultimately, such research will contribute to a deeper understanding of the truth humanity seeks—namely, the fundamental laws of the universe.
