In context of progress of Theory of Everything.
'Theorists believe that there is a fundamental unity underlying the fundamental forces of Nature. If they are right (and they may not be), gravity is, at bottom, just one more facet of a single 'super force', of which the strong, weak and electromagnetic forces are also just a part. Yet according to Einstein, gravity is a manifestation of something completely different: curvature of space and time.'
These are the theories which create a deep schism preventing the unification Theory of Everything.
However adding a fifth dimension to the equations gives a better view.
'Theodore Kaluza (in 1919) found if General Relativity theory was written out for a five-dimensional universe instead, it resulted in Einstein's theory and the laws of electromagnetism. Could it be that electromagnetism is merely a manifestation of gravity in some hidden, fifth dimension of the universe?'
- Robert Matthews in 'Unravelling the Mind of God - Mysteries at the Frontiers of Science' 1992