Does Physics Discover Reality, or Does It Build Models of It?
Does Physics Discover Reality, or Does It Build Models of It?*
The question at its core contains the eternal division and competition between experimental and theoretical physics. It was only in the 4th century BC in ancient Greece that the knowledge of reality was placed on a solid scientific basis by Aristotle, who created the science of Logic and put all human thinking into categories. From that moment on, the scientific revolution accelerated its course. In the 17th century Galileo Galilei, through a series of experiments, laid the foundations of mechanics. A few decades later, Isaac Newton set the theoretical framework by formulating his three famous laws. It is evident that for most of history until the 20th century, the model of physics was a scientific experiment or observation, from there new data about reality, and finally a theoretical summary.
At the end of the 19th century, an experiment was conducted that I want to focus on because it marked a turning point. After James Maxwell formulated the basic principles of electromagnetism, most physicists in the world believed in the existence of the “ether” - an invisible substance that fills all space, which creates the medium for the movement of light. Two experimenters, Albert Michelson and Edward Morley, decided to prove this statement experimentally by building a precise interferometer with which to measure the speed of light in different directions. They reasoned that since the Earth moves in the “ether” in a certain direction, light should have a different speed depending on the direction of measurement, since its speed must be added to or subtracted from the speed of movement of the Earth relative to the “ether”. To everyone’s great surprise, no difference in the speed of light was found, which led to the denial of the “ether” by the majority of physicists at the time and the search for a new theoretical framework. It is important to note, however, that if we look closely at the data, the experiment only shows that the speed of light is constant with respect to the measuring instrument, and Michelson and Morley themselves did not categorically claim in their report that the “ether” did not exist - they only reported that the measured speed was “probably less than one-sixth” of the expected one (Michelson and Morley, 1887). From that moment on, physics has been pushed permanently in the direction of building theoretical models, a process that is still valid today.
What has changed so much since the experiment I described? If I have to answer in a few words: after Michelson and Morley, mathematicians completely took over the field of physics. First, George FitzGerald suggested that all bodies decrease in length in the direction in which they move, just enough so that our instruments perceive the speed of light equally in all directions (FitzGerald, 1889). After him, Hendrik Lorentz developed the idea and mathematically showed that the mass of a particle increases with its speed and tends to infinity as it approaches the speed of light, which sets the limit that no material body can move faster than light in the space we know (Lorentz, 1904). All these are mathematical constructions built not on new observations, but on a single failed and perhaps misinterpreted experiment.
And this direction leads to the masterpiece of Albert Einstein and the creation of the most beautiful and elegant model of the world, called the Special Theory of Relativity. In 1905, Einstein did not start from the laboratory, but from an axiom, namely that the speed of light is constant for all observers, and from this single statement he derived a whole new geometry of space-time, in which space and time are relative, and mass and energy are equivalent (Einstein, 1905). Only three years later, in 1908, did Hermann Minkowski take Einstein’s theory and reformulate it on a geometric basis, showing that the constancy of light does not need to be postulated separately, but emerges as a natural consequence of the structure of the four-dimensional space-time that today bears his name (Minkowski, 1908).
It would take a lot of space to describe everything that happened in the twentieth century with the other major branch of physics, called quantum mechanics, but what is important from the point of view of our topic is that almost always in quantum physics the pattern of progress is the following: the creation of a theoretical mathematical model of reality, which is subsequently (often many years later), proven experimentally. In the double-slit experiment, for example, a single photon produces an interference pattern identical to a wave, passing through both slits at the same time, and if we try to determine which slit it passed through, the interference disappears, which means that observation does not simply record reality, but changes it. The wave function describes the particle not by a position in space, but by a mathematical formula in an abstract Hilbert space that has nothing to do with the geometry of the physical world we live in. Physicists have debated for more than a century whether it is a model of reality or reality itself, and the fact that the question remains open is itself telling. Calculations based on Erwin Schrödinger’s equation from 1926 work with incredible precision (Schrödinger, 1926). But why exactly they work, no one has yet been able to satisfactorily explain.
Modern efforts in quantum physics are very reminiscent of peeling an onion, where removing one layer leads to the next. First, we discovered that everything is made up of atoms, then we found that atoms are made up of electrons, protons, and neutrons, and the last two nuclear particles are made up of quarks, which together with the electron are a manifestation of energy fields or perhaps even smaller structures that we now call “strings”, vibrating in several dimensions.
Undoubtedly, the last few years have also been exciting for experimental physics, given the discovery of the Higgs boson at the LHC in 2012 and of gravitational waves through the LIGO experiment in 2015, but the important thing is that both discoveries, however significant, only confirm predictions of theorists made many decades before. The same can be said for a number of other discoveries from the late 20th and early 21st centuries, such as the discovery of the top quark, the Bose-Einstein condensate, and the demonstration of quantum entanglement, all of which were theoretically substantiated long before they were experimentally proven. The only significant exception to the rule that the theoretical model precedes the experiment is dark matter, which was first inferred not from a theory, but from direct astronomical observations of galaxies and galaxy clusters.
At the same time, with the apparent lagging behind of experimental physics, there has been a strong development of theoretical physics. Edward Witten proposed the latest version of string theory (Witten, 1995), on the basis of which Juan Maldacena developed the theory known as AdS/CFT duality, which describes how strings relate to the field theories describing the three quantum forces—the strong and weak nuclear forces and the electromagnetic force—and shows mathematically how quantum mechanics and general relativity can be connected (Maldacena, 1998). Mark van Raamsdonk took this idea to its logical conclusion, arguing that spacetime itself is made up of quantum entanglement between particles, that is, if we reduce the entanglement between two regions, the spatial connection between them weakens, and if we remove it entirely, the geometry collapses (Van Raamsdonk, 2010). Space in this model is not the arena in which things happen, but a consequence of the relations between quantum states, in the same way that temperature is a consequence of the collective motion of molecules, without any molecule being “hot”. Thus, space-time is not primordial or given, but a consequence of the quantum field.
If space-time itself, that is, the arena in which physics has discovered reality since Galileo, turns out to be a construct built of quantum relations, then the question in the prompt is turned on its head: what exactly have we been discovering all this time? Perhaps we have been discovering not reality, but the limits of our models—and each new model has shown us not the next layer of reality, but the next layer of our ignorance.
I firmly believe that in the 21st century, physics will mainly build mathematical theoretical models of reality, which will be increasingly difficult to prove experimentally, not because physics has moved away from reality, but because reality turns out to be much deeper in micro or macro terms than our instruments can measure. There are a whole bunch of questions that have yet to be answered: Why is the gravitational force weaker than the other three fundamental forces? Where does dark energy come from? What is dark matter? I eagerly await the moment when the grand unified theory will be created, which will connect quantum mechanics with general relativity, so that we can get to the next layer in peeling the onion and discover a whole new world of questions, ideas, and mysteries beneath it.
References
1. Michelson, A.A. and Morley, E.W. (1887) ‘On the Relative Motion of the Earth and the Luminiferous Ether’, American Journal of Science, 34, pp. 333–345.
2. FitzGerald, G.F. (1889) ‘The Ether and the Earth’s Atmosphere’, Science, 13, p. 390.
3. Lorentz, H.A. (1904) ‘Electromagnetic Phenomena in a System Moving with Any Velocity Smaller than That of Light’, Proceedings of the Royal Netherlands Academy of Arts and Sciences, 6, pp. 809–831.
4. Einstein, A. (1905) ‘Zur Elektrodynamik bewegter Körper’, Annalen der Physik, 17, pp. 891–921.
5. Minkowski, H. (1908) ‘Die Grundgleichungen für die elektromagnetischen Vorgänge in bewegten Körpern’, Nachrichten von der Gesellschaft der Wissenschaften zu Göttingen, pp. 53–111.
6. Schrödinger, E. (1926) ‘Quantisierung als Eigenwertproblem’, Annalen der Physik, 79, pp. 361–376.
7. Witten, E. (1995) ‘String Theory Dynamics in Various Dimensions’, Nuclear Physics B, 443, pp. 85–126.
8. Maldacena, J. (1998) ‘The Large N Limit of Superconformal Field Theories and Supergravity’, Advances in Theoretical and Mathematical Physics, 2, pp. 231–252.
9. Van Raamsdonk, M. (2010) ‘Building Up Spacetime with Quantum Entanglement’, General Relativity and Gravitation, 42(10), pp. 2323–2329.
*The essay was written for The Physics Minds Underground Essay Competition 2026