There are currently some problems that hinder a unified comprehension of Physics. Lee Smolin (in The Trouble with Physics, 2006) has listed 5 major problems:

   1. Combine general relativity and quantum theory into a single theory.
   2. Resolve the problems in the foundations of quantum mechanics.
   3. Determine whether or not the various particles and forces can be unified in a theory that explains them all as manifestations of a single, fundamental entity.
   4. Explain how the values of the free constants in the standard model of particle physics are chosen in nature.
   5. Explain dark matter and dark energy.

— Wikipedia

2010.11.30 Tuesday ACHK