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182<br />
THE FOURTH DIMENSION<br />
square in the transference along the blue axis by which<br />
this cube is generated from the orange face. This<br />
purple square made by the motion of the red line is<br />
the same purple face that we saw before as a series of<br />
lines in the section b1, b2, b3. Here, since both red and<br />
blue axes are in our space, we have no need of duration<br />
to represent the area they determine. In the motion<br />
of the tesseract across space this purple face would<br />
instantly disappear.<br />
From the orange face, which is common to the initial<br />
cubes in fig. 107 and fig. 108, there goes in the blue<br />
direction a cube coloured brown. This brown cube is<br />
now all in our space, because each of its three axes run<br />
in space directions, up, away, to the left. It is the same<br />
brown cube which appeared as the successive faces on the<br />
sections b1, b2, b3. Having all its three axes in our<br />
space, it is given in extension; no part of it needs to<br />
be represented as a succession. <strong>The</strong> tesseract is now<br />
in a new position with regard to our space, and when<br />
it moves across our space the brown cube instantly<br />
disappears.<br />
In order to exhibit the other region of the tesseract<br />
we must remember that now the white line runs in the<br />
unknown dimension. Where shall we put the section<br />
at distances along the line? Any arbitrary position in<br />
our space will do; there is no way by which we can<br />
represent their real position.<br />
However, as the brown cube comes off from the orange<br />
face to the left, let us put these successive sections to<br />
the left. We can call them wh0, wh1, wh2, wh3, wh4,<br />
because they are sections along the white axis, which<br />
now runs in the unknown dimension.<br />
Running from the purple square in the white direction<br />
we find the light purple cube. This is represented in the<br />
sections wh1, wh2, wh3, fig. 108. It is the same cube