The crisis of modern physics witnessed by many manifests itself in a split between academic departments:
- Physics: Instrumentalism/formalism/epistemology (what we can say).
- Philosophy: Realism (what is).
A realist philosopher is not welcome at a physics department, and what would an instrumentalist physicist do at a philosophy department?
A split between physics and philosophy of physics indicates that something is fundamentally wrong, and that comes out as a crisis. What is then fundamentally wrong?
Let us search the root of trouble in the formation of modern physics in the beginning of the 20th century in the new fields of Einstein's Special Theory of Relativity SR and Quantum Mechanics QM.
Both SR and QM express instrumentalism and formalism as being focussed on measurement assuming a certain formal structure (Lorentz invariance and Hilbert space structure) where the real nature of physics is left open because it is believed to be hidden to inspection. The focus is thus on epistemology as what a physicist can measure and report (to motivate public funding). This is the physics performed at the Large Hadron Collider at CERN in Geneva. Very expensive with real physics hidden in a blip on a screen.
But the question of what physics is as ontology of reality remains, and paradoxically that is what philosophers of physics outside physics departments focus on (Reichenbach, Bell, Maudlin, Brown).
So is there any hope to get out of the crisis by joining departments of physics and philosophy of physics into one?
Can SR and QM be reformulated into theories about reality, which start from real physics instead of formalism?
Any theory about reality must start from some fundamental reality expressed in Postulates of the theory. If the Postulates carry no physics, a theory based on the Postulates using logic cannot carry any physics.
The Postulates of SR are
- Physical laws are Lorentz invariant.
- Speed of light is to be measured by physicists according to SI standard to give exactly the value 299,792,458 metres per second.
We see that the Postulates of SR are like commands to be followed by physicists but say nothing precise about any physics. Therefore SR does not say anything about physics, unless physics somehow is added to the Postulates. And that is what Einstein did by using a "thought experiment" to conclude that two light signals viewed by two observers in fact are the same and so must connect by a Lorentz transformation. But the conclusion of the same had no physical basis and so was picked from the sky suddenly adding physics to the Postulates, but then physics without reality.
The Postulates of QM were formalised by the mathematician von Neumann into a set of abstract axioms:
- State space: A system corresponds to a Hilbert space. States are rays (or density operators) in it.
- Observables: Physical quantities are self-adjoint operators on the Hilbert space.
- Measurements: Outcomes are eigenvalues; probabilities are given by the Born rule.
- Dynamics: Time evolution is unitary, governed by the Schrödinger equation.
We see that 1-3 are like commands to quantum physicists, without concern to real physics. Von Neumann did this during the heydays of Hilbert's formalism in the 1930s, which however soon died because of Gödel.
Altogether, we see that SR and QM are not realist theories starting from what is as ontology, but have clear qualities of formalism/epistemology as what we can say. The trouble with formalism is that there is no reality to decide and so the discussion can continue forever like in medieval scholastics.
My contributions to a realist restart are:
MMR starts from a reality where different observers use different coordinate systems and seeks what agreement can reached.
RealQM starts from a classical realist continuum model of systems of charge densities in shared 3d Euclidean space interacting by Coulomb potentials as a new type of Schrödinger equation.
Both MMR and RealQM represent realism as what is and so express unification of physics and philosophy of physics.
Here are three steps to formalism away from realism:
- Planck introduces smallest quanta $h\nu$ in 1900.
- Einstein introduces photon as quanta of light $h\nu$ in 1905.
- Heisenberg introduces QM as matrix mechanics in 1925.
In 1927 Schrödinger left QM because realism or "Anschaulichkeit" was lacking. Schrödinger's equation for the Hydrogen atom is a realist model, but for atoms with more than one electron it is a formalist model without physics.