Is physics describing reality, phenomena or measurements?
It is important to understand the distinction between reality, phenomena and measurements. It is also important to be aware of the distinction between physical reality and higher (subtler) states of reality. One could even talk about the ultimate (absolute) reality.
We all know that physics does not even attempt to describe the subtler reality. Physicists don’t know where to start. The common perception among the people is that physics describes the physical reality by discovering the laws of nature.
Does physics describe the physical reality? The answer is no. It is clear to all physicists that physics does not describe the physical reality per se. Physics theories are models of the physical reality.
No theory, mathematical or not, can describe reality because direct perception of reality is not possible. We perceive the physical reality around us through the nervous system. The physical interaction is translated into electrical pulses in our sensory nerves. These pulses are then converted into an information package by the brain and finally the information package is interpreted by the mind. We don’t know what mind is but we know that the incoming information has to be interpreted otherwise there is no perception.
Human mind is interpreting the perception. Physics theories are interpreting the interpretation. If we call the “interpretation” a model, a physics theory is a model of a model. Theory is a mental construct and it is a model of a model. Physics theories are removed from reality by at least 2 levels.
Physics models (theories) may not be close to reality but they still work. They still make accurate predictions about the outcomes of measurements. They also point to new things as in new particles or elements that can exist but have not been observed yet.
In science we talk about the laws of nature. That is arrogant talk! Properly speaking we have models of physical reality. These models are subject to change. Models get better and better but they can never describe physical reality completely. Physicists keep this in mind but they still call their models theories because theory sounds better. Theory also sounds final but it is not. Physics theories will be updated as we gain more insights into the cosmic mysteries.
The common aspect of all physics theories is dynamics. All physics theories have to describe the evolution of the physical system quantitatively. Everything is changing in nature; physics has to describe the change quantitatively. The term “phenomena” emphasizes the dynamic aspect of the physical reality. In this sense we can say that physical theories describe phenomena.
The dynamic picture gets a little confusing in Quantum Mechanics. This does not mean that physical reality is different at the microscopic scale necessarily. The physical reality is what it is. We don’t know what it is really like. We can devise models to predict its behavior in a particular system or in a particular measurement apparatus but that’s all we can do. Simply because we have 2 different theories, Quantum Mechanics and Classical Mechanics for the microscopic and macroscopic worlds, respectively, it does not mean that we have 2 different physical realities.
Mathematical formalism known as the Quantum Mechanics (QM) describes the outcomes of measurements performed with elementary particles when they interact with each other or external fields. QM effects manifest when elementary particles are confined to small volumes by the fields they are interacting with. When they interact, elementary particles create the confinement field for each other. In an atom, the electric field created by the positively charged protons in the nucleus captures and confines the negatively charged electrons. Captured electrons behave differently than free electrons. This is the essence of QM. You may want to read what I wrote earlier on this point: New Perspective on the Quantum Mechanical Nature: Seeking Freedom.
Measurement is the key concept in QM. Measurement is like taking a snapshot of the ever-changing reality. Snapshot is a static picture but the physical reality is dynamic so this static view is already different from reality. When we perceive the snapshot our perception is removed from reality by one more level and finally when we devise a model to describe the measured outcomes the model will be removed from reality by 3 levels. This is the situation with QM. It is a theory that is removed from reality by 3 levels.
In classical physics we model the phenomena (dynamic aspects) and hope that measurements (snapshots) conform to the model. Quantum Mechanics works in the opposite direction. Quantum Mechanics was developed by modeling the measurement results (snapshots). The dynamics (time evolution of the quantum system) is an add-on. In other words, it is very difficult to develop a movie from snapshot pictures. This is done in cinema, of course, but in the physics of the microscopic world developing a movie from snapshots is extremely difficult. At each measurement (snapshot) the wavefunction collapses and yields a single state of the system. Stitching together the snapshots belonging to different collapsed states to come up with the dynamical behavior of the system may be totally meaningless. This is the root cause of the many non-classical aspects of the Quantum Mechanics.
In my next post, I will focus on the QM wavefunction and its many interpretations.