Leo and CCC, you are both thinking of space as real, while I’m trying to sneak in the notion that it is not.
Let me start with sound. Is sound real? One cannot answer that question without first defining, in some sense, what sound is. When a tree falls (as in the over-used conundrum), it creates some pressure waves in the air. If there is somebody around, then the pressure waves hit their ears. The ears perform a spectrum analysis and send the corresponding electrical signals to the brains. And in the brains, some neurons fire in some specialized areas. This is the whole chain. Physically, there is nothing more. We have a falling tree, pressure waves, electrical signals mapping frequencies, some neurons firing. Where is sound? Sound, in my opinion, is the magic that the brain performs. Is it real? In my opinion, no; it is just a cognitive picture the particular evolutionary process that we are part of chose to equip us with. It is a mapping of our auditory signals.
In an exact parallel, we should think of space as a cognitive mapping our brain creates out of our visual inputs. True, our touch and auditory senses provide some corroborating evidence to this picture. Just as the pressure waves created by a falling tree are sound only if we are there to hear it, the random photons floating around are space and a universe with stars and galaxies only if we are here to process them.
I know this argument may sound a bit abrupt. After all, I wrote a whole book dealing with this notion, and I’m not sure I convinced anybody yet! Now the real interesting question is, are there photons or pressure waves to begin with? They are a part of the cognitive picture we have created for ourselves – something Leo rightly pointed out earlier.
Now, coming back to the question of 3-D space, I believe that our binocular vision really resulted in our brain creating this particular representation of 3-D space. If we had only one eye, the brain probably wouldâ€™ve evolved a picture where the size of a predator representing the level of the corresponding danger (for instance). Just like the intensity of sound gives us a clue as to the distance of its source. Of course, this is all my speculation…
Leo, you write simulation programs? Wonder if you could figure out how bats would perceive motion using echolocation? My guess is that it would be exactly like special relativity with the speed of light replaced with the speed of sound.