As of 2009, no satisfactory theory of quantum gravity has been advanced, and the possibility that one could be constructed remains in dispute.<ref>[http://www.sciencemag.org/cgi/content/summary/325/5941/673 "Can Gravity and Quantum Particles Be Reconciled After All?", Sciencemag.org]</ref> | As of 2009, no satisfactory theory of quantum gravity has been advanced, and the possibility that one could be constructed remains in dispute.<ref>[http://www.sciencemag.org/cgi/content/summary/325/5941/673 "Can Gravity and Quantum Particles Be Reconciled After All?", Sciencemag.org]</ref> |