Yes Graham, you're perfectly correct. It seems that if we use a dimension more, in one way or another, as a brane or as something 'infinitely small' there becomes new approaches to what SpaceTime might be.

FIVE-DI don't like the idea(s) myself though

That as I do think what we see is what we get. (WYSIWYG)

A simple principle that suits me. The world we exist in is 'real'.

Matter do exist, SpaceTime have certain 'forces' and 'laws' macroscopically. Others at a QM level.

Times arrow is what generates the change macroscopically, and has nothing to do with us 'conning ourselves'.

And then I'm not as sure as most on what 'dimensions' are either

Most seem to see SpaceTime as some different 'pieces/dimensions' wedged together by 'forces' into a SpaceTime. I prefer a concept where what we got was a 'symmetry' already from the beginning, expressed 'materializing' through 'emergences' where each one creates new properties that we finally observe as SpaceTime.

And in that motto I don't expect us to be able to prove for example 'two dimensionality' existing in our 3D world (and times arrow). Just ponder how such a system would express itself in a 3D world. It would be visible from some angles, disappear from other. I've never seen any experiment proofing that concept (2D in a 3D + times arrow) and I don't expect to see one either.

But if dimensions was something 'singular' this experiment should exist, and I'm not talking about mathematical models here. It should be proof able here and now.

So, without it I'm still wondering what 3D really is. The best approximation I got too is as 'emergence's', and the thing I see as defining it would then be the 'arrow of time'. And then it comes down to geometry and how the plasticity of our Space-Time creates just different geometry's simultaneously, depending on your frame of reference for its definition.

And if that universe would exist you can't pick it apart. Although it doesn't exclude different 'dimensionality's' as you as easily could have a two, three, four or a fifty six dimensioned universe i would expect each one of them to be 'self sufficient and whole' in themselves. No loose dimensions to pickle together that is

or 'pressing in' our '3D + times arrow' in that fifty sixth universe f.ex.

And that's also why I'm doubting 'distances' too. And times arrow will have to be the answer to 'distances' and it have a relation to mass and acceleration, and space and 'matter' will then have to be 'emergences' from ? And there I don't know anymore, or rather I don't want to guess anymore:)

But I differ between time and its arrow. I think time is a different concept from what we see as the arrow.

But it's quite easy to prove it wrong. Just introduce a real 2D matter object into SpaceTime and show me how it disappear from certain angles as it will contain f.ex. width and length but no depth (height).

If dimensions are 'pick able' it seems to me that such objects should exist already. And if they're not existing?