For many decades, the assumption in physics has been that all the forces, including gravity, must be quantized - that is, we must look and find the quantum theory for gravity. And that the key to the "theory of everything" rests on that great discovery waiting to happen.
But decades of work by the top theoretical and mathematical minds of multiple generations have not resulted in any testable theories. A good question to ask is: does gravity have to be quantized? Maybe, just maybe, gravity in this universe is 'classical' and continuous, and really just the result of warps in spacetime as Einstein proposed in general relativity! Some physicists are asking just that type of question, and developing theories based on gravity being classical with the others - electromagnetism and the strong and weak nuclear forces - follow quantum field theories. Maybe, just maybe, this is the reason gravity is SO different from the others and so difficult to link into the Standard Model. I am really interested in seeing how this evolves, and may very well create testable experiments in the near future...something that has not happened yet for quantum models of gravity. In the end, experimental results will determine how things really work.
