Lee Smolin - The Trouble with Physics

The five great problems in theoretical physics

1. Combining Quantum Mechanics and Relativity in a background independent way as relativity requires a space time (background) that evolves. There is also the problems of determinism,different observational perspectives and continuity of space and time.
   
2. Resolve the foundational problems of quantum mechanics that deal with the problems of realism and determinism to avoid the problem of observers.
3. Determine whether the particles and forces can be united in a single theory. This means combining bosons with fermions with the introduction of a limited number of tuning constants.
4. Explain how the free constants of the standard model occur - why do they take their particular values?
5. Deal with the problems of dark matter and dark energy - the apparent contradictions of general relativity at the galactic scale with respect to acceleration and the need for a positive cosmological constant for the accelerating expansion of the universe.