I came up with this line somewhere:

To properly experience $n$ dimensions the retina of the organism should be at least of $n-1$ dimensions.

And human eye has $2$ dimensional retina, so we can experience at most 3 dimensions properly.

Now my question is:

  1. Do more than 3 dimensions exist?

  2. What is the proof that 'there exist only 3' or 'more dimensions do exist'?

  • 3
    $\begingroup$ Unrelated to dimensions, but multiple instances of "do" in your title do exist. $\endgroup$ – Marc van Leeuwen Nov 27 '15 at 9:18
  • $\begingroup$ I doubt this assertion. Our 2-dimensional retina can by no means observe the third dimension, as is demonstrated with lots of optical illusions. We only have a 2-dimensional projection to work with which can be the result of an infinite number of 3-dimensional arrangements. With two eyes/retinas the situation is different but one could argue that the resulting overall optical system is actually 3-dimensional. $\endgroup$ – Peter - Reinstate Monica Nov 27 '15 at 10:54
  • $\begingroup$ On the contrary I would contend that in order to fully observe 3-dimensional objects including their insides one needs an 4-dimensional retina, or at least one with 3 dimensions of which one is orthogonal to the dimensions of the object. We as 3-D beings can fully grok a surface, but another surface in the same plane as the observed one could not. Same with 3 dimensions. In order to look inside a body you need another dimension. $\endgroup$ – Peter - Reinstate Monica Nov 27 '15 at 10:58
  • $\begingroup$ It's interesting to note that jumpings spiders have several retina layers, so the are three-dimensional. $\endgroup$ – jinawee Nov 27 '15 at 12:49

Well, I suppose we could add time as a 4th. However, apart from that there is no experimental evidence whatsoever for more than 3 spacial dimensions. String Theory and its friends remain theories with negligible experimental evidence in their favor.

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  • $\begingroup$ Well this makes me feel, whats that thing which travels along this dimension $\endgroup$ – user92340 Nov 27 '15 at 8:09
  • $\begingroup$ And if time is considered the 4th dimension, then the retina is actually 3-dimensional, and indeed we can observe 3-dimensional objects traveling through time, with us ;-). $\endgroup$ – Peter - Reinstate Monica Nov 27 '15 at 10:50