The ultimate goal of physics is to create a single equation which can be applied anywhere in the universe. It is quite sure that we are not there yet and there is a long journey ahead of humankind to achieve that ultimate goal of physics. During the past four centuries we have progressed a lot due to some intelligent minds and still are progressing. Every step in physics created a conflict and solving that conflict, we got new ideas, new set of equations which led us to easier life and better understanding of the universe.
Three conflicts in the field of physics are most common. The first conflict was recognized as far back as the late 1800s. The first conflict was created by puzzling properties of light. According to laws of motion presented by Isaac Newton, if you run fast enough, you can catch up with a departing beam of light, whereas according to laws of electromagnetism presented by James Clerk Maxwell, you can't. In order to solve this Einstein came in and solved this conflict through his theory of special relativity.
Einstein completely inverted our understanding of space and time. According to theory of special relativity, everyone experience space and time in a different way. Einstein said form and appearance of space and time depend on one's state of motion. The motion became relative and the conflict with the speed of light was solved. Special relativity while solving one conflict created another conflict. One conclusion of Einstein's theory is that no object can travel faster than the speed of light, but Newton's experimentally successful universal theory of gravitation involves impacts that are spread over vast distances of space instantaneously.
To solve this conflict Einstein presented his theory of general relativity. This theory made a clear view of gravity in the minds of scientists and in fact, in a short time people could actually imagine what gravity is and how it is transmitted.
According to General Theory of Relativity fabric of space and time transmit the force of gravity from one place to another. Once again the pattern repeated itself: The discovery of general relativity, while solving one conflict, led to another. Physicists have developed quantum mechanics in 1930s. Reason of the development of quantum mechanics was, a number of problems arose when Einstein’s equations and nineteenth-century ideas of physics were applied to the atomic world. The third conflict was the deepest conflict created by the incompatibility between general relativity and quantum mechanics. To solve this conflict, scientists that we are familiar with and most of them are alive created a different theory and set of equations.
Scientists offered string theory to solve the third conflict. Most of us think that our universe has three spatial dimensions, but string theory creates more dimensions that are beyond our vision. String theory was built using special and general relativity, but string theory needs its own plain restoring of our conceptions of space and time. Present form of String Theory was created by well-known scientists like Michio Kaku.