Hi Jim,
I think the same about the extradimensions. It is like a fashion now inside the theoretical sciences community, it is due mainly to strings , Mtheory, Superstrings or the geonetrodynamics with points and with the geometrical algebras, they consider all now in majority that we have extradimensions, it is also due to their philosophy considering only the photons and strings or ppoints inside in 1D oscillating vibrating connected with a 1D cosmic field of this GR. So with the maths of strings they have extrapolated 10d, 11d,26d .
I don t understand to be frank why this fashion, maybe they are in a prison due to these photons and GR alone and they believe that a kind of god or a mathematical accident creates the topologies , geometries with these fields and extradimensions. Personally I have found enormous ontological and philosophical rpoblems considering this philosophy. In fact these tools in maths about the extradimensiobns are just tools, like we have create the geometry in 2D with the squares, triangles.... they permit to better create architectures or others but the universe and our reality is always in a pure 3D , so I consider these extradimensions too like simply tools wich are not really reals in our pure 3D. Now they have difficulties these thinkers to return at this old school of our pure 3D and the motions of particles. Clifford, Lie, Hopf are relevant tools for our quantum fields, the problem is not there, the problem is to generalise this GR and geom alg and fields like the cause of our quantum mechanics at my humble opinion. I beleive strongly that the fields are emergent, not the particles wich are in a superfluidity and permit the emergent baryonic matter.
But these thinkers have learnt a lot at the universities and the strings are teached even for their PhD it is very odd because they are an assumption generally and philosophically speaking.
They cannot change their lines of reasoning now, they are persuaded and endoctrinated I must say, Einstein and Witten have created a philosophical prison and now they turn in round inside , I am a problem with my theory but that could converge in unifying the DE, the DM, the GR, the QM, the QFT, the strings and these pure 3D spheres, but they don t recognise this due to this endoctrination and the vanity. Regards, friendly