The Big Bang’s mysteries and unsolvable “first cause” problem: The “first cause” problem may forever remain unsolved, as it doesn’t fit with the way we do science. (Marcelo Gleiser, 4/06/24, Big Think)

The origin of the Universe pushes the boundaries of what we can understand. Simply put, most of science is based on two things: objectivity and causality. Objectivity asks for a clear separation between the observer and what is being observed. Causality assumes an ordering in time whereby an effect is preceded by a cause. As I pointed out in a recent book with my colleagues Adam Frank and Evan Thompson, the origin of the Universe brings both causality and objectivity to a halt. And it does so in a very different way from quantum physics, where both principles are also challenged. Quantum mechanics blurs the separation between observer and observed and substitutes deterministic evolution by probabilistic inference. It is, however, still a causal theory since an electron will respond to, say, an electromagnetic force in ways dictated by well-known dynamical causes (with, for a technical example, a Coulomb potential in Schrödinger’s equation). There are known forces at play that will induce specific dynamical behaviors.

But when it comes to the origin of the Universe, we don’t know what forces are at play. We actually can’t know, since to know such force (or better, such fields and their interactions) would necessitate knowledge of the initial state of the Universe. And how could we possibly glean information from such a state in some uncontroversial way? In more prosaic terms, it would mean that we could know what the Universe was like as it came into existence. This would require a god’s eye view of the initial state of the Universe, a kind of objective separation between us and the proto-Universe that is about to become the Universe we live in. It would mean we had a complete knowledge of all the physical forces in the Universe, a final theory of everything. But how could we ever know if what we call the theory of everything is a complete description of all that exists? We couldn’t, as this would assume we know all of physical reality, which is an impossibility. There could always be another force of nature, lurking in the shadows of our ignorance.

At the origin of the Universe, the very notion of cause and objectivity get entangled into a single unknowable, since we can’t possibly know the initial state of the Universe. We can, of course, construct models and test them against what we can measure of the Universe. But concordance is not a criterion for certainty. Different models may lead to the same concordance — the Universe we see — but we wouldn’t be able to distinguish between them since they come from an unknowable initial state. The first cause — the cause that must be uncaused and that unleashed all other causes — lies beyond the reach of scientific methodology as we know it.