Theorists are obsessed with superstrings and blackholes. But reality offers quantum entanglement with no explanation of gravity. It's as if nature is telling us: Hey, why worry about strings when you have me to experiment on?
Physicists are skeptical of gravity manipulation. But consider a system of two quantum entangled photons. Newtonian gravity says that the force between two masses separated by distance r is given by F = GMm/r^2. How many steps would you have to glean to go from Newtonian gravity to gravity manipulation? I count 3 leaps of intuition.
1. The effective mass of a photon is m = hf/c^2. So two entangled photons do have mass, therefore, there is a tiny acceleration field between them.
2. Space does what mass tells it to according to the Einstein equations. However, that doesn't mean we can't manipulate the entanglement between two photons to get back something that looks like a gravity field.
3. We control the entangled photons p1 and p2. Photons can travel along a fiber optic cable. In theory, we could align the optical fiber along the radii of a spinning disk. Then, we could centrifuge the p1 photon along the blueshift direction and centrifuge the p2 photon along the redshift direction. It would be similar to storing gravitational potential energy between the two entangled photons.
Physicists are prepared to wait a thousand years for someone to prove this mathematically. But the experiment, while challenging and sophisticated, would be easier to perform.