Does space itself exist? This question has concerned the greatest minds of physics. Simply put:
If every object in the universe disappeared, would space still be there?
Newton saw space as the canvas upon which God painted, so it would still exist even without objects. In contrast Leibniz considered a substance without properties unthinkable, so to him space was just a concept based on object relations, just as a meter is defined as the distance between two marks on a platinum-iridium bar in Paris. He concluded that if objects only move with respect to each other, without matter there would be no space.
Newton’s reply to Leibniz was a hanging bucket of water that spun around (Figure 2.2). First the bucket spins, not the water, then the water also spins and presses up against the side to make a concave surface. If the water spins with respect to another object, what is it? It can’t be the bucket, because when it initially spins relative to the water the surface is flat, and when later it is concave, the bucket and the water spin at the same speed. In a universe where all movement is relative, a spinning bucket should be indistinguishable from one that is still. If an ice skater spins in a stadium their arms splay out by the spin. One could see this as relative movement, as the stadium spinning round the skater, but why then do the skater’s arms splay? He concluded that the skater really is spinning in space (Greene, 2004) p32.
This seemed to settle the matter until Einstein showed that objects actually do move relative to each other. Mach then tried to resurrect Leibniz’s idea, arguing that the water in Newton’s bucket rotated with respect to all the matter of the universe. So in a truly empty universe, Newton’s bucket would stay flat and a spinning skater’s arms would not splay. This isn’t testable, as one can’t empty the universe, but this resort to speculation reflects how disturbing some physicists find the idea of a space that is:
“…substantial enough to provide the ultimate absolute benchmark for motion.” (Greene, 2004) p37
In contrast, a virtual space could handle object interactions in two ways:
1. Centralized. In this option each photon has an absolute position and every cycle all positions are compared to see if any are equal, i.e. if a collision has occurred. For the inhabitants of this virtual reality, space would indeed be truly nothing and potentially continuous. Yet from a processing perspective, it is inefficient as every point has to be compared to every other point every quantum cycle, which task grows geometrically with the number of interactions. For a simulation the size of our universe, the processing is unimaginable.
2. Distributed. In this option, each point of space is a node with a fixed processing capacity pre-allocated. Now collisions aren’t based on central calculations but on local overloads that occur if a node gets more processing than it can handle. This limits the processing required better and as space expands it also adds more processing. In this virtual reality, space isn’t continuous and does exist apart from the objects in it.
Reverse engineering prefers the second option in which the processing is limited. It implies that our space is like a TV screen that can show “nothing” or perhaps static but is always there. A point of “empty” space is then a node of the quantum network that is null processing, just as a point on a TV screen can show nothing instead of a dot. So if every object in space disappeared space would still exist, just as a screen still exists even if no image is shown. And it is also the current verdict of many in physics that:
“space-time is a something” (Greene, 2004) p75
Space as a quantum processing network is neither the passive canvas of Newton nor the nothing of Leibniz because it is null processing, which is active despite having a null output.