An actual snake eating its tail would bloat with excrement, burst open and die as a fetid blob of septic entrails. Life, it turns out, cannot escape entropy. It is not self-sustaining. This metaphor applies equally to the notion of a grand unified theory tying the small world of quantum behaviour with the grand arcs of relativistic space. Such a theory would bloat due to Gödel incompleteness and eventually disintegrate into uncertainty. Indeed, a universe based on unified laws would also consume itself, so we should be glad that we live between two irreconcilable theories. Each saves us from the other.
Stated formally, Gödel’s theorem of incompleteness seems bland to the point of irrelevance: essentially, no logical system can consistently define itself; or more generally, all information systems must be contained within a larger information system. But applied acutely, it means that no particle can contain a complete definition of itself, and that the definition of the universe cannot be contained within the information in the universe.
The conformal bootstrap may have already consumed emergent quantum theory, freeing the tail of the snake from the jaws of its head; which is probably for the best because theories of emergence have a nasty habit of being circular and solipsistic (“to predict well-known public events several years after they have occurred is not perhaps the most demanding of tasks for an educated mind”). So, even when emergence succeeds mathematically it fails philosophically. Circular reasoning, it should be noted, is acceptable in mathematics because it establishes the validity of harmonics, and math is the study of harmonic patterns, but it is not tolerated in philosophy because causation can only go one way. An infinite loop arises if both x causes y and y causes x are said to be true, which is thermodynamically impossible and philosophically unacceptable. This same circle of thought bedevils democratic political science, where leadership by the people devolves into leaders chasing the whims of their followers.
This leaves us with the whole body of the snake, the entropy of the universe from small to big, as the closest we will ever come to a grand unified theory. Entropy – messy, unpredictable, annoying and unsatisfying – may be the best we can do.