To restate the situation, we have the theory of general relativity (gravity) and quantum physics. Both are bedrocks of modern physics. Both are accurate to a high degree of experimental precision. Both aren’t compatible – with each other. Apparently, one (or both) of these theories must be wrong, or at best incomplete. That’s why the Physics unification of the two (a theory of Quantum Gravity) is physics’ Holy Grail. However, that Holy Grail is proving as difficult to find as the Biblical Grail itself! But for the moment, it appears as if the universe has two independent sets of laws (or sets of running software) – one governing the very large (gravity); one the very small (the quantum). This makes no natural or scientific sense.
We have observations of four physical forces yet no theory which unites the three quantum forces (electromagnetism, the strong nuclear force and the weak nuclear force) with the one classical force – gravity. Theory needs to be satisfied. All of the four fundamental forces should be interconnected; some sort of unification principle must be in operation that relates all four, one to the other. However, these four fundamental forces that govern the Universe show no signs of any obvious unification – well actually the three quantum ones do (known as the GUT – Grand Unified Theory), but that’s where the unification ends. Gravity remains the wallflower. If the Big Bang theory is to be proven correct as stated, scientists must of necessity come up with a viable theory of Quantum Gravity that is an acceptable unification of the trio of quantum forces with gravity. There is, to date, no viable theory of Quantum Gravity despite thousands of physicists searching for one over many generations now. Even for the final 30 years of his life Einstein searched for his big TOE but never found it.
In summary, the realm of the micro and the realm of the macro are incompatible, like two different sets of software that are separate and apart but collectively run the cosmos. Again, that makes no sense. It should be relatively easy to unify all four forces. Einstein and thousands in his footsteps have found out the hard way that it’s damn hard to get a TOE. Mother Nature is a bitch!
Now, the real question is what are the implications if there is no such animal as a unified theory or a TOE? What if we have a case of never have so many spent so much time and effort over so little (actually nothing)? With the passage of every day, the missing TOE appears unlikely ever to be found. Then what?