on “the extensive discussions of de Broglie’s pilot-wave theory” and,
on Born and Heisenberg’s presentation of a ‘quantum mechanics’ apparently lacking in wave function collapse or fundamental time evolution.

[T]here are subtler difficulties that arise when we go over from considering the Universe simply as a very large system to considering it as the totality of what exists.

All one can say is that if the Universe was originally uniform then the small irregularities that arise from statistical fluctuations would not develop into galaxies in the time available.

At the foundations of physics there is today confusion and incoherence. … GR and QM have opened a revolution. The revolution is not yet complete.

[A]t small scales there should be quanta of space and time ….

The quest for quantum gravity can be separated into three main lines of research. … They are often denoted “covariant,” “canonical,” and “sum-over-histories,” even if these names can be misleading and are often used interchangeably. They cannot be characterized by a precise definition. . . .

Quantum gravity is therefore the study of the structure of spacetime at the quantum scale.

I think it is fair to say that there isn’t even a single complete and consistent candidate for a quantum theory of gravity.

[P]hysics is once more facing conceptual problems: What is matter? What is causality? What is the role of the observer in physics? What is time? What is the meaning of ‘being somewhere’? What is the meaning of ‘now’? What is the meaning of ‘moving’? Is motion to be defined with respect to objects or with respect to space?