On Sat, 27 Jul 2013 00:43:51 +0200, Warp <war### [at] tagpovrayorg> wrote:

> Orchid Win7 v1 <voi### [at] devnull> wrote:
>> > That one is easy. Simply because our eyes can only see in 2d. We can
>> > perceive 3d images because of the stereoscopic effect of having 2  
>> eyes.
>
> Perceiving three-dimensional space is not related to stereoscopic vision.
> It helps, but it isn't what makes it three-dimensional perception.
>
>> That doesn't explain why visible objects around us only move in 3
>> dimensions. If there were more dimensions and we should somehow only
>> "see" 3 of them, we should see objects constantly zipping into and out
>> of the 3D slice we can perceive.
>
> Talking about slices is, as I see it, nonsensical. A camera doesn't see
> a "slice" of the three-dimensional space. It sees a *projection*, which
> is a completely different thing. If there were a fourth dimension that's
> like the other three, we would likewise see a three-dimensional  
> projection
> of it, not a slice.
>

I imagined it this way:
Imagine a swimming pool with the water surface as a 2d universe. The  
beings in this universe cannot see anything that is not the water surface.  
When you step into the water they perceive first small circular  
shapes(your toes) merging into a oval shape, etc. The don't see a  
projection of your 3d body, they see a slice.
So I assume that we (3d beings) would only be able to see a 3d slice of a  
4d object.

> Anyway, according to general relativity, spacetime *is* four-dimensional,
> and everything actually moves in the fourth dimension all the time.
> Moreover, the reason why gravity (seemingly) accelerates objects is
> because of this movement in 4-dimensional spacetime. (The spacetime is
> curved, which is what causes the apparent acceleration. In reality it's
> not acceleration but inertia.)
>
> So, technically speaking, when you drop an object, you are seeing  
> movement
> in the fourth dimension (or, more precisely, the effects of the curvature
> of spacetime, from which we see a 3-dimensional projection, which is what
> causes us to perceive it as accelerating motion, even though in reality
> it's just inertial motion. It's a similar idea as how a railroad seems
> to converge at the horizon in a photograph.)
>

What if time could have more dimensions? That would be interesting. A  
being in 2-dimensional time could see back and forth in our 1d time.

-- 
-Nekar Xenos-

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