Things are tricky:

`A torus diameter is 4R ! But the torus radius is only R! So its a matter`

`of perspective.`

`If you look at the same distance circle radius "torus 2 radii" then the`

`4D radius - seen in 3D - is longer!`

J.W. On 17.09.2020 23:15, Robin wrote:

In reply to Jürg Wyttenbach's message of Thu, 17 Sep 2020 22:04:39 +0200: Hi,You can look up SO(4) in Wikipedia The group measure is 2^1/2. This is the length of the unit radius of the Clifford torus (formed by the tangent space). To get the standard norm (=1) you have to divide by 2^1/2!Thank you, this now makes sense. Since 2^1/2 = 1.414... then the 4D radius is larger than the 3D radius, however previously you wrote:- "R_4D = 1/2 R_p *(2^1/2 )" , which would make the 4D radius less than the 3D radius?? (Assuming that R_p is the 3D radius.) IOW where does the factor of "1/2" come from?Or more simple. The radius for the standard circle is 1, but the Clifford torus has two radii, thus its length is (1+1)^1/2(Pythagoras :- length of the hypotenuse. 4th dimension perpendicular to other 3.)J.W.[snip]

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