I've thought a lot about Maxwell's equations. As you know, the SI system of units has abolished the exact values of vacuum permeability and permittivity since 2019. They must now be found experimentally but the uncertainty is enormous.
However, the product of permeability and vacuum permittivity has the dimensions of the inverse square of a velocity.
Don't you think that this product is the inverse of the square of the wave propagation speed of the earth's electromagnetic field?
I think it makes sense if you understand Maxwell's equations a certain way when you apply them in the vacuum of Earth. In addition, if the earth's electromagnetic field fluctuates, this product may also fluctuate. What do you think???
I await your response and I would like to collaborate with you if you agree with me.