Idiot. EM and gravitation do not unify, even if you are wearing Kaluza-Klein jeans.

Class. Quantum Grav. 17 4125 (2000)
It is possible to obtain exactly the Maxwell equations from the Einstein field equation, but there is a long list of caveats that inevitably breaks the analogy with electromagnetism.

The source of monopole radiation is a changing monopole moment for a charge q or for a mass m. Since charge and mass are conserved, there can be neither monopole electromagnetic radiation nor monopole gravitational radiation.

The source of dipole radiation is a changing dipole moment. (Punctiliously, you need a second time derivative of the dipole moment.) For a pair of charges

d = qr + q'r'

and there's nothing special about the derivatives. For a pair of masses, the gravitational dipole moment is

d = mr + m'r'

and its time derivative is

mv + m'v' = p + p'

By conservation of momentum the second time derivative of the gravitational dipole moment is zero, and you can go to a center of momentum frame and set the first derivative to zero as well. There is no gravitational "electric dipole" radiation.

Consider the analog of "magnetic dipole" radiation. The gravitational equivalent of the magnetic dipole moment for a pair of charges is

M = mv x r + m'v' x r'
("x" is the cross product, "mv" is the "mass current")

But M is the total angular momentum, which is also conserved. There is no gravitational "magnetic dipole" radiation.

The next moment up is quadrupole, with no relevant conservation laws, so gravitational quadrupole radiation is permitted. You can use this argument to advocate that gravity must be a tensorial (spin-2) interaction. Electromagnetism is mediated by spin-1 photons.


Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz3.pdf