General relativity is the theoretical structure that governs the universe on a large scale, while quantum mechanics governs it on a small scale. The two theories are incompatible, and in their current states cannot both be correct. Separately, their predictions are very accurate. Normally physicists choose one or the other theory which is appropriate for their situation. This works well when you are dealing with small, light things like particles in which case you would use quantum mechanics, or if you are dealing with large, heavy things like stars in which case you would use general relativity. Sometimes this approach doesn't work. In the cases of black holes and the big bang, you are dealing with something very heavy that is also very small. If you try to combine quantum mechanics and relativity in these situations, you are presented with infinite answers that just don't make sense. Even if you are willing to leave the big bang and black holes in a shadow of mystery, it still is difficult to swallow that on the universe's most basic level, its laws are divided.

There is a theory currently under development that may solve this conflict. It is based on the assumption that particles are really one-dimensional loops called strings, and is fittingly known as string theory. Before string theory, particles were thought of as infinitely small zero-dimensional points. By changing our view of what particles really are, quantum mechanics and relativity coalesce into a greater whole. In fact, string theory not only allows for both theories, it requires them. It is the first theory to offer a possible solution to our problem. In the process, it changes our concept of space by adding more spatial dimensions, with these extras curled up into the folded fabric of space.

Besides uniting quantum mechanics and relativity, many physicists and mathematicians are convinced that string theory could unify the four forces of nature and describe all matter. If it can meet this challenge, it may be the so-called Theory of Everything or unified field theory that Einstein searched for in vain for more than three decades. (At that time, the existence of the nuclear forces were unknown, so he was only dealing with the two forces of electromagnetism and gravity.)

If we were to discover a theory of everything, people called reductionists claim that we can know everything including the emotions and actions of people. Others claim that this is untrue because as a system becomes more complicated, because of chaos theory, it becomes too difficult to predict. Most physicists believe that if a T.O.E. (Theory of Everything) was discovered, it would not be an end to physics or any other science, but a grand new beginning.