"We don't even fully understand gravity."
We Really don't understand gravity.
http://www.esa.int/SPECIALS/GSP/SEM0L6OVGJE_0.html
A gravitational effect from electro-magnetism (spinning superconductor).
I don't believe that this is actually an effect of electromagnetism; the spinning mass (supposedly) creates a gravi-magnetism force related to gravity in a manner analagous to the way magnetism is related to electricity. The superconductors are used because the electrons are totally free of electrical "friction" and the minute effect is clearly manifested, if I'm not mistaken (and I may very well be...).