With the recent discovery of a new boson, which is likely to be the elusive Higgs boson, the standard model for particle physics would not be complete. Keep in mind that this only confirms the model that has been used for a long time now. This explains the early moments after the big bang where there was the electroweak force which separated and became the electromagnetic and weak nuclear forces (there’s also the strong nuclear force). This doesn’t unify the theory of gravity. Physicists must still develop a theory of quantum gravity.
For every particle there is a corresponding symmetric particle. Physics has a translational symmetry, which means that the laws and values of physics are the same at every location in the universe. If an observer were to travel from one point to a much farther distant point the observer we see no change in the physics. A broken symmetry introduces change—a non-absolute uniformity. The breaking of symmetries creates complexity in the laws of nature in the outcome of laws. There’s a symmetry and uniformity between the strong and weak nuclear forces, which have been unified as electromagnetism by James Clerk Maxwell. A typical example of vital symmetry breaking is that which gives rise to the balance between matter and antimatter in the early universe. However, there is an asymmetry between the quantum and the large (a la gravity). String theory is the attempt to unify all of physics.
If photons are fired through the experiment one at a time (firing photons at a wall with two holes and a photon detector on the other side of the holes), they will build up an interference patter on the other side, as if they had gone through both holes at once and interfered with themselves. If the experiment is set up so that detectors monitor which hole the photo goes through, the photon is indeed observed to be going through only one hole, and there is no interference pattern. If a detector is set up not at the holes but intermediate between the two holes and the back wall detector screen then it may be possible to see which route a particular photon took after it had passed the two holes before it arrived at the screen.