Physics has made 'great progress' over the last decennia. The technological advances which have resulted in highly intricate devices leave this impression at least. In the physical sciences many insights have been gained which have contributed to the ability to advance technology. Despite all those advances it can be questioned whether deep insight really has been obtained in the true character of nature. Highly intricate theories of physics leave the impression that they do reflect reality and, therefore, that we do understand nature. As an example, no experiment has been found contradicting Quantum Theory leaving the impression that the theory must be correct. I maintain that Quantum Theory is a mathematically sophisticated way to describe nature, but does not give deep understanding of its character, a point which can be argued as follows.
It is not widely acknowledged (and probably often even denied by many physicists) that modern physics consists of a patchwork of incomplete and mutually inconsistent theories lacking the ability to understand the essence of fundamental physical notions such as space, time and particle mass.
Using several examples, I think that in order to make progress towards a truly universal and self-consistent description of nature the current approach toward physics likely needs to be reconsidered despite the claim that 'great progress' has been made. The so-called progress has largely been made at the expense of introducing many different mathematical structures thereby decreasing the ability to obtain a single coherent description of nature. In fact, often those formalisms have created their own 'abstract spaces' lacking a natural or exact relation with real nature and incorporating various inconsistencies.
The purpose of this article is to provide several illustrations of the above claim to reconsider the current approach towards physics.
1. The Character of Fundamental Notions
Modern physics is unable to explain the true physical character of such notions as time, space, energy, mass, momentum, Planck's constant, electromagnetic charge, gravity and de Broglie's matter wave function. All these notions are normally assumed to obtain their meaning as part of mathematical relations in which they are used. Great efforts have been devoted to explain notions in terms of relations, which is obviously bound to fail due to their mutual dependencies.
In contemporary theories the notions of time and space obtain their 'meaning' by the relativistic Lorentz transformations relating space-time in two different inertial reference frames. Within a single frame space and time they are always used as an input parameter to mathematical expressions describing behavior of other entities within that frame. This still leaves any true understanding of the nature of space and time completely open.
Furthermore, in contemporary physics it is assumed that time and space have a continuous character and can be identified mathematically with the set of real numbers, subject to the additional constraint that time can only evolve in the direction of increasing numbers. According to the Heisenberg uncertainty relation Δ E Δ t ≥ ħ /2 the uncertainty in time can be arbitrarily small which seems to be point towards a continuous character of time. On the other hand, de Broglie's (in practice hardly used) energy relation of a stationary massive particle E=mc2 = hv0, with v0 equal to the 'internal frequency' of the particle, seems to point to existence of a smallest time interval corresponding to Δ t0=1/v0. For moving particles, this time interval gets expanded due to relativistic behavior. A smaller time interval than Δ t0 cannot exist for a given massive particle, otherwise it would violate the above energy relation and consequently the existence of the particle itself. Therefore, it can be concluded that either Heisenberg's uncertainty relation or de Broglie's energy-frequency relation must be erroneous.
Another issue that remains a continuing mystery concerns the apparent unidirectional evolution time. Most theoretical relations involve time as a reversible parameter. This again suggests that something fundamentally is lacking in the understanding in the physical character of time thereby allowing theoretical expressions to be 'time symmetric'.
According to de Broglie's wave relation h=λB m v (where λ is de Broglie's wavelength, m the relativistic mass, and v is the velocity of the particle). With momentum p=mv, it follows that h=p λB, which is an exact relation for a uniformly moving massive particle, i.e., it does not express any uncertainty. The Heisenberg momentum momentum-location uncertainty relation on the other hand corresponds with the expression h<= Δ p Δ x with Δ p and Δ x the uncertainties in momentum and location of the particle. This relation resembles the form of de Broglie's relation, although in the latter case uncertainties play a role. Suppose that the momentum p is exactly known, then λB is exactly known according to de Broglie. But, according to Heisenberg's uncertainty relation Δ x equals infinity. However, in particle experiments the momentum can be measured with good accuracy and the uncertainty of the location of the particle is bounded since one knows that it must be in a specific area after measurement. In conclusion, one can question the simultaneous validity of the relations of de Broglie and Heisenberg.
In modern physics space is considered the environment in which objects exist or propagate. Consequently, space and objects are considered different in nature although it is assumed that space needs to exist for objects to exist. Since the nature of space and material objects is not fully understood, it is clear that the assumed separation between the two might be incorrect and some more advanced insights are needed to comprehend their nature.
Time is different from space because the former does not have symmetrical characteristics and therefore cannot be considered a 'dimension' in the same way as spatial dimensions.
According to Einstein's well-known relation E=mc2, free mass can be identified with energy although neither the nature of energy nor mass is fully understood. It can be surmised that if Einstein's relation is physically truly understood for a stationary particle then its meaning will also reveal the nature of relativistic mass.
Electromagnetic charge is used as a parameter in mathematical field expression. However, the cause of charge remains unknown.
Planck's constant h appears in many quantum physical relations and is also referred to as the quantum of action. The relation between Planck's constant and classical action remains obscure. Often it is claimed that in the limit of h converging to zero one obtains classical behavior, although this gives rise to other contradictions such as massive particle behavior turning in photonic behavior.
From these illustrations it can be concluded that in order to obtain a true understanding of nature it remains absolutely indispensable to get an understanding of the physical meaning individual quantities such that also the real nature their relations involving such quantities is revealed.
2. Mathematical Models
Contemporary physics employs many different mathematical models or 'spaces' to describe natural phenomena. Several examples can be provided which all have their specific issues in terms of matching theory with reality:
Quantum theory applies the concept of Hilbert space to describe state functions. For every 'problem' in quantum physics a specific Hilbert space needs to be constructed in order to describe the physical phenomenon under consideration. This situation appears quite artificial as for each 'problem' a physicist is necessary to invent a model to match nature instead of relying on a basic physical description of nature to describe all quantum phenomena independent of any physicist and which always provides an unambiguous 1-1 match with nature.
The mathematical model used in physics also have a flavor of incompleteness. For instance, according to conventional quantum physics, upon measurement, quantum state functions consisting of a superposition of eigenfunctions can collapse into one of the randomly selected eigenfunctions. The physical mechanism by which this random selection and state collapse takes place is unknown.
Modern quantum field theories describe creation and annihilation of particles in terms of operators as if nature applies operators on itself to determine the existence of particles. The operation of such operators is also very much discontinuous since it transitions a non-existing state (particle) into something existing (or vice verse). The physical details of such transition are not and cannot be described by the operation of the operator. Again this seems to be a case where theory might provide 'good' answers to practical physical 'problems' but cannot be considered the ultimate complete or correct way to describe nature.
Most physical theories implicitly assume the existence of continuous time and space. Using this assumption all kinds of theorems are developed from basic postulates. It can be expected that many of those theorems should be discarded or be viewed as approximations when it turns out that space and time have a discrete nature. The continuous space-time theorems may create mathematical artifacts which are physically non-existent.
3. The Relation between Theory and Measurements
In physics it is nowadays not uncommon to read statements where a difference between experimental and theoretical results in the order of many percentages but are still proclaimed as a 'great success' or an 'excellent confirmation' of a particular theory. This dangerous and careless attitude leaves an impression that further experimental work is hardly necessary to verify the theory used to describe the considered phenomenon. The following example illustrates the point that a critical attitude towards theory remains necessary.
The standard model of particle physics contains 20 free parameters which need to be measured experimentally to match theory with experiment. A critical observer might indicate that the theory resembles a sheet stretched over an object which is stitched at the 'best' locations to match the shape of the object. From the observation of the sheet's contours it is impossible to draw any precise conclusions about the actual nature of the object. Identifying the sheet with the real object obviously provides a flawed perspective of reality. Therefore, the standard model of particle physics can hardly be considered a fundamental theory.
4. Patchwork of Theories
As mentioned earlier, modern physics is practiced based on a set of 'working models' or theories which are generally considered the best possible current approximations of a more general universal theory but the assumed models have a limited effective applicability range. Some examples of effective applicability ranges of theories are low velocities (classical mechanics), low gravitational strength (classical mechanics, special relativity theory, quantum mechanics), macroscopic scales (general relativity theory), or at very small scales (quantum theories).
5. Scaling
Quantum-like phenomena occur at the level of individual quantum particles (electron and atoms) but also in case of large aggregates of particles such as with lasers and super-conduction phenomena. Even cosmic phenomena like the emission of radiation beams by neutron stars likely require an explanation in terms of quantum behavior. Gravitation is probably intricately involved in quantum behavior because it has an omni-present character. A single coherent theory or principle is required in order to describe quantum, electromagnetic and gravitational phenomena at all possible scales. Such universal principle or theory would have to encompass or allow derivation of all possible known laws of nature.
6. Research and the Education of Physics
Over the last century a fundamental shift has taken place in the way physics is approached in terms of research and education due to the emergence of 'new physics'. This new 'new physics' can largely be understood as a major transition from the application of theoretical descriptions relying on a minimal set of mathematical tools towards the use of a multifold of highly sophisticated mathematical models. In many fields of physics, trying to comprehend existing theories and contributing to research has become a highly time-consuming and specialized effort, which appears to migrate the practice of physics much further away from to the real goal to find a smallest set of universal principles from which all structure and behavior can be simply explained.
Students largely obtain an understanding of physics by learning laws and solving problems. They hardly spend any time deliberating the cause of these relations or considering the true character of individual quantities. When such issues are addressed at all, they are often part of a philosophy course. Consequently, the practice of physics has become an exercise in understanding abstract relations and not what physics is supposed to be about, namely the study of gaining insight in the true nature of individual quantities and their relations. The obvious reason why physics has primarily resorted to the study of relations between physical quantities is a severe lack of deep insight in the character of nature.
7. Final Considerations
At the start of this discussion, the claim was made that some aspects of the current approach toward physics likely need to be revised, which was argued based on a few examples. The majority of the physicists are unlikely to agree with the statements made here, because no alternative has been provided here that convincingly will change their opinion.