Spacetime is the stage where the great illusion unfolds. It is the fabric of the macrocosmic universe, the matrix underlying the holodeck.

But how real is it?

Certainly it is real in the sense of scientifically verifiable. Experiments confirm how space and time interact in the four-dimensional spacetime field. The empirical reality of spacetime is not subject to reasonable doubt.

So is spacetime the underlying reality beneath the great macrocosmic illusion? Is it fundamental? Is it real in that sense?

Probably not.

Spacetime began, and if it can begin, it can end

Physics says that spacetime began early in the history of the universe and that without the Big Bang spacetime might not exist.

We don’t know what, if anything, was before spacetime; we don’t know what, if anything, could follow spacetime. Before the Big Bang the entire universe could have been subsumed in a singularity without time or spatial dimension. There could have been nothing at all, just a vacuum of “nothingness” with random quantum fluctuations.[1]

The future of the universe also could be a singularity. Or perhaps with all free energy spent and entropy at its maximum, there could be nothing remaining but the seeming stillness of quantum interactions in a state of universal thermodynamic equilibrium.

Whatever the universe was, or will be, there is something more fundamental than spacetime. Spacetime began.

What is beneath spacetime?

We think of the universe as spacetime and a collection of galaxies and stars and planets, comprised of microscopic particles and fundamental forces that shape all things and events. But is the universe composed of core components at all? Or is what we conceive as the underlying microscopic reality of the universe also an illusion? Is there something more fundamental than either the macroscopic world of galaxies and stars or the microscopic world of electrons and atoms?

We know that the objects that curve and bend spacetime are not themselves solid as they appear. They have massive gravitational fields but are little more than empty space containing orbiting or vibrating wave-like semi-particles held together by forces more fundamental than their own gravitational mass. The tiniest semi-particles in the universe are knots of energy interacting in patterns constantly, and every physical “thing” is at its deepest level a process or interaction. Beneath the hood reality is not a collection of irreducible substances, but interactions and processes and events that give rise to the illusion of substances.[2]

We know that time is not absolute and unchanging, that the processes, events, and interactions that drive the universe are not arranged in lockstep chronological order. At the most fundamental level of known reality, the arrow of time does not drive a chronological history of distinct events. Instead, at the quantum level, there are no distinct events, but only a stream of wave functions describing the probability amplitudes of an almost infinite spectrum of possibilities. Instead of driving events, entropy and the Second Law of Thermodynamics may only influence the shape of those microcosmic wave functions. It is only above the level of the microcosm, in the great illusion of the macrocosmic universe, that wave function amplitudes become actual probabilities resolving into unique outcomes and the distinct events of history.

Is the microcosmic core of the universe nothing more than a timeless lake of entangled possibilities arranged in order of probability by the physical laws of the quantum wave function? Or beneath even that, is it a vacuum of nothingness comprised only of random bursts of quantum fluctuation? Is this the underlying reality from which the great illusion has sprung in some way that we do not understand?

Spacetime is not fundamental reality

The great illusion may not be the macrocosmic universe as we know it, the world of countless galaxies with trillions of stars and planets, the world of mountains and oceans. Perhaps the ultimate illusion is the world of spacetime itself and the laws of physics that govern the interactions of what we perceive as objects in spacetime. Entropy and the laws of physics and the reality of local time and relative time may not underlie the illusion; they may be the illusion, the very things that comprise the holodeck and our reality.

Beneath it all may be only the quantum wave function itself—ceaseless interactions, entanglements, and superpositioned possibilities—somehow resolving into a stage where all probabilities play out. Perhaps everything else is imagined and illusory, a way of talking about reality, but no more real than mountains and oceans and waves crashing on the shore.[3]

So no, spacetime is probably not real in the sense of the fundamental basis of the universe. It is a constructed stage. Constructed out of the many possibilities inherent in the quantum universe—for us and all other things and entities that exist in the universe. It is our stage, but it is not the bottom of what is real.

---

[1] Keen (2013).

[2] “The world is not a collection of things, it is a collection of events.” Rovelli (2017), p. 98.

[3] “Not only does the deepest layer of reality not consist of things like “oceans” and “mountains”; it doesn’t even consist of things like “electrons” and “photons.” It’s just the quantum wave function. Everything else is a convenient way of talking.” Carroll (2017), p. 171.