Electromagnetism in a gravity field for the quaternion gravity proposal

Gravity effects everything, almost. The electromagnetic field strength tensor has no dependence on a metric tensor because $$A^{\mu,\nu}-A^{\nu,\mu}=A^{\mu;\nu}-A^{\nu;\mu}.$$ The energy density of an electromagnetic field is invariant in a gravity field. Photons as a quantum are effected by gravity as shown through light bending and red shift experiments suggesting a conflict between theory and experiment. The space-times-time invariance as gravity proposal uses quaternions instead of tensor calculus. Two observers look at two different events. They calculate the difference, then take the square: $$(dt,dx/c,dy/c,dz/c)^2=(dt^2-(dx^2+dy^2+dz^2)/c^2, 2dt dx/c,2dt dy/c,2dt dz/c).$$ The first term is an interval, the other three space-times-time. If the two observers agree on the interval, a constant velocity exists between the two. If the two observers agree on the three space-times-time values, that invariance is the quaternion gravity proposal. The electric field will remain invariant in a gravity field, but not the magnetic field. Why? The electric field is the number of quantum electric charges, unchanged by a gravitational field. The magnetic field is those charges in motion. Motion is changed by gravity. Quaternion gravity may be more consistent for electromagnetism than GR.