So, why does the electron have the mass it has? And what happened after the big bang that created all of the particles in the universe? Why are there so many particles, protons, pions, neutrinos, quarks? And why did the big bang happen? What was there before the big bang?

To answer such questions, one would need a theory that describes all of the forces of nature, all of the particles of nature, and interactions between particles and forces, in one mathematical framework. The recently developed string theory can achieve these requirements. The book by Brian Green describes how.

The idea of Super String Theory is that all elementary particles of matter and forces are tiny loops, like rubber bands. These loops vibrate. Their vibrational patterns determine the mass, spin, motion, and other properties of a particle.

There are currently two widely accepted views of the world. One is quantum mechanics, which deals with a tiny world, and another is the theory of relativity, which describes the world of huge speeds, distances and masses. It so happens, that they conflict with one another. Using quantum mechanics, one can answer a question concerning the states of a tiny particle or a group of particles. In general relativity, things are very different. One performs calculations that compute the evolution and structure of an entire universe at a time. Thus, there is a definite rift between quantum mechanics and general relativity. The Super String theory is viewed to be able to bridge this gap.

In order for string theory to be accepted as a theory of everything, among other things, it would certainly have to include Quantum theory and Relativity. All of the quantum properties of a particle are determined by the vibrational patterns of the string. The theory of relativity deals with curvature of space as a result of the constant speed of light. Depending on the curvature of space, the string either stretches or contracts, resulting in a slightly different vibrational pattern.

So why strings? Why not cubes or spirals? The answer is simple. String theory originated when scientists did an experiment (the details of which I will not go into) that they could describe only using vibrating loops, and nothing else. Then other physicists noticed that the same mathematical principle could describe other phenomena. As time progressed, physicists found more and more phenomena for which this loop theory was true, until it became evident that all the current knowledge could be described using vibrating loops. However, some enhancements were made to string theory for it to become the theory of everything.
The most important enhancement is the addition of six more dimensions. Modern physics works like this: given the conditions of an experiment, a scientist uses a theory to predict the most probable result. In some cases, using a string theory with a loop vibrating in three dimensions, one would get infinite or negative probabilities, which make no sense. In order for this to not happen, the string would have to vibrate in nine space dimensions, and one time dimension.

Where are these extra dimensions? In every point of space. Just like a garden hose, whose surface is two dimensional, can appear one-dimensional from a distance, the six extra dimensions are hidden, curled up.