Hi Hugh,
thank you for your reply. I'm afraid I did not explain myself clearly. You wrote: "I am not sure that a lower dimension would provide a more relaxed environment for high-D structures (wouldn't they feel "squashed" by the restriction?)"
Not at all. Let me explain. I'm talking about a dynamic, vibrating structure, for which dimensionality is one of its attributes. Going from higher to a lower dimension does not 'squash' it but *unfolds* it. Take an example of a tesseract. Its surface is 8 cubes. You can stack these 8 cubes in 3D, in effect rearranging the 4-volume into a 3-volume; and the length the edge of this 'dimensionally reduced' object becomes twice as long. That's how, in fact, I understand the expansion of space, i.e. the higher-dimensional structure 'relaxes' into a (n-1) structure, which increases the length of its edges.
Also, when I spoke about your Landscape Test, I had quantum theory in mind, not the macro world. I am not clear yet --have to reread your essay-- how exactly you apply it to the Earth surface.
.
I'm pursuing the answer to the question: Why the universe is 4D? Why not 5, or pick any other number. I strongly believe that there is a good reason for this; and my hunch is that, topologically, 4D offers the maximum number of symmetries => in 4D the structure of space finds its lowest energy state.
When mathematicians and physicists deal with higher dimensions, the objects they consider are limited mostly to points, vectors and fields consisting of points and vectors. Those are 0 or 1-dimensional objects. But a real object, in real n-space, is essentially a segment of that space. For example, a cloud is a familiar object in 3D and so is a billiard ball. Their densities may differ, but ultimately, both are just segments of space with clearly delineated boundaries. These boundaries is what makes them 'real objects' as opposed to points and vectors -- even when a boundary wraps 'emptiness'.
Now, regarding 'real objects' in n-D, there is a topological theorem, the details of which I can't recall now, but hope you could remember -- and it says that some important ratio of... surface to.. 'something' -? reaches the limit of infinity already at n=7. This implies that there are not that many 'real spaces' that can contain 'real objects', and 4D is very special.
Again, there _is_ a clear, logical and unambiguous answer to the question 'Why 4D?' I am looking for it.
Thank you very much for all your input,
-Marina