What if we are so used to the curvature of space caused by mass and the range of its effects that we totally ignore the possibility of the existence of "opposite" curvature1, i.e. objects that bend space opposite to mass and cause repulsion by creating local space anisotropy?
What if we are so used to space curvature caused by mass that we invent a force that has no charge to explain possible effects of opposite curvature (repelling force - diamagnetism)?
What if the oscillating electric field has the ability to cause tiny local (anisotropy) fluctuations in space and its effects on objects are interpreted as "magnetic field"?
Could magnets be just an example of objects with anomalous gravitational fields due to their ability to distort the isotropy of space?
I guess my question boils down to:
How do we know that the force at the poles of a magnet is not gravitational (large but local curvature caused by anisotropy) with opposite signs, rather than what we call magnetic?
Can space curvature arise from something else different than mass?
What would change on the r.h.s of the Einstein's equation (components of stress-energy tensor) if we assume a connection with torsion?
1. Same size of the volume element $dV$, but with stretch in one element, say $dx$ and proportional compression in the other two $dy$, $dz$.