Quantum mechanics leads to macroscopic superposition!
How nature avoids macroscopic superposition?
Quantum evolution leads to superposition of many curved space-time!
How nature maintains flat space approximation?
General relativity predicts wormholes!
Problem of Time:
Quantum gravity does not give an explicit time variable! n How to understand time in quantum gravity?
Mathematics of standard model have become quite complex!
How to unify the Particles?