Physicists so far have formulated partialtheories to explain the universe. The ultimate goal is to bring all of thesetheories into a complete unified theory. Einstein spent his later years tryingto search for it but he failed.
This is because though the laws of gravity andelectromagnetic forces have been established; little was known when it comes tonuclear force at that time. Moreover, Einstein did not accept the uncertaintyprinciple. Yet it seems that the uncertainty principle is a basic component ofthe universe. Therefore, it must be incorporated in the theory. At the start of the century, the generalidea was that everything could be described using the properties of matter,such as heat conduction and electricity. The discovery of uncertainty principleand atomic structure put an end to this assumption. In 1928, it was thoughtthat if an equation could be found to explain protons much like Dirac’s equationto electrons, it would conclude theoretical physics.
The discovery of neutronand other nuclear forces, however, crushed this idea. These imply that weshould not be overconfident. The pursuit for the ultimate theory is a tedioustask.The GUT or grand unified theory broughttogether the partial theories of the weak, the strong, and the electromagneticforces. However, it requires quantities, like the relative mass of particles tobe chosen so they would comply with the predictions.
This makes GUTunsatisfactory along with the fact that it does not include gravity. The maindifficulty lies in the fact that general relativity is a “classical” theory. Itdoes not incorporate the uncertainty principle like in quantum mechanics. When Stephen Hawking applied uncertaintyprinciple in general relativity, he has yielded fascinating hypothesis. One isthat black holes are not really black and another is that the universe iscompletely self-contained and without boundary.
Uncertainty principle impliesthat empty space is not actually empty. It is filled with pairs of virtualparticles and antiparticles.