[freedomjusticeruleoflaw]

Theoretical physicists will tell you that for the most part advancements in polishing the standard model are stuck. There has been many efforts to find the unified field theory etc. None have held up to scrutiny. This too shall pass away.

[Nateman]

String theory had a lot of promise. The difficulty lies in describing what all those extra dimensions have in them. The choices possible are a staggering number so most physicists have thrown up their hands and given up pursuing the theory. As is typically the case in science , to unravel this Gordian knot they will have to cut away small pieces over a long period of time.

[Rockingham]

The two largest components of modern physics -- quantum mechanics and relativity -- work quite well in isolation. They are not complete though and have not been merged into a single unified theory that works at every level, from the subatomic to the cosmic. Moreover, mysterious dark energy and dark matter seem evident from astronomical observations as to the workings of gravity, but their nature and that of gravity itself are not at all understood.

Various string theories that postulate extra dimensions attempt to explain the forces and fields that physics discerns in a unified way, but, as you point out, no string theory has yet passed scrutiny. We seem to be in an impasse similar to the crisis of classical physics in the late 19th and early 20th century.

My guess is that the answer will come from someone on the margins like Einstein once was, a physics doctoral student whose dissertation had been rejected, earning an income as a Swiss patent reviewer while he wrote four extraordinary papers that revolutionized physics.