The observed deviations from the laws of gravity of Newton and Einstein in galaxies and clusters can logically speaking be either due to unseen dark matter particles or due to a change in the way gravity works. Until recently there was little reason to doubt that general relativity correctly describes gravity in all circumstances. In the past few years insights from black hole physics and string theory have lead to a new theoretical framework in which the gravitational laws are derived from the microscopic quantum entanglement contained in the vacuum. An essential ingredient in the derivation of the Einstein equations is that the vacuum entanglement obeys an area law, a condition that is known to hold in Anti-de Sitter space. In a Universe with a positive dark energy, like de Sitter space, the microscopic entanglement entropy contains, in addition to the area law, a volume law contribution whose total contribution precisely matches the Bekenstein-Hawking entropy for the cosmological horizon.  This extra volume law contribution leads to modifications in the emergent laws of gravity, which precisely explain the observed phenomena in galaxies and clusters currently attributed to dark matter.