In Search of Quantum Gravity

What is there that is new to be learnt, concerning brains or minds, from what we have seen in the last chapter? Though we may have glimpsed some of the all-embracing physical principles underlying the directionality of our perceived ‘flow of time’, we seem, so far, to have gained no insights into the question of why we perceive time to flow or, indeed, why we perceive at all. In my opinion, much more radical ideas are needed. My presentation so far has not been particularly radical, though I have sometimes provided a different emphasis from what is usual. We have made our acquaintance with the second law of thermodynamics, and I have attempted to persuade the reader that the origin of this lawpresented to us by Nature in the particular form that she has indeed chosen - can be traced to an enormous geometrical constraint on the big bang origin of the universe: the Weyl curvature hypothesis. Some cosmologists might prefer to characterize this initial constraint somewhat differently, but such a restriction on the initial singularity is indeed necessary. The deductions that I am about to draw from this hypothesis will be considerably less conventional than is the hypothesis itself. I claim that we shall need a change in the very framework of the quantum theory! This change is to play its role when quantum mechanics becomes appropriately united with general relativity, i.e. in the sought-for theory of quantum gravity. Most physicists do not believe that quantum theory needs to change when it is united with general relativity. Moreover, they would argue that on a scale relevant to our brains the physical effects of any quantum gravity must be totally insignificant! They would say (very reasonably) that although such physical effects might indeed be important at the absurdly tiny distance scale known as the Planck length - which is 10-35 m, some 100000000000000000000 times smaller than the size of the tiniest subatomic particle - these effects should have no direct relevance whatever to phenomena at the far far larger ‘ordinary’ scales of, say, down only to 10-12m, where the chemical or electrical processes that are important to brain activity hold sway.