From the link:
Its interesting to note that Einstein spent the better part of his life trying to develop a unified field theory combining gravity with electromagnetism, and was ultimately unsuccessful.
It is known that gravity, electromagnetism and spacetime are coupled phenomena. Evidence includes the bending of light, the red-shifting of light, and the slowing of time in a gravitational field. This coupling is most prominently described by General Relativity [25]. Given this coupling and our technological proficiency for electromagnetics, it has been speculated that it may become possible to use electromagnetic technology to manipulate inertia, gravity, or spacetime to induce propulsive forces
Its interesting to note that Einstein spent the better part of his life trying to develop a unified field theory combining gravity with electromagnetism, and was ultimately unsuccessful.