The Cosmic Quest for the Theory of the Universe
Michio Kaku and Jennifer Thompson
First Anchor Books Edition
Copyright @ 1995 by Michio Kaku and Jennifer Trainer Thompson
Superstrings: A theory of Everything?
The superstring theory assumes that the ultimate building blocks of nature consist of tiny vibrating strings. If correct, this means that the protons and neutrons in all matter, everything from our bodies to the farthest star, are ultimately made up of strings. Nobody has seen these strings because they are much too small to be observed. (They are about 100 billion billion times smaller than a proton.) According to the superstring theory, our world only appears to be made of point particles, because our measuring devices are too crude to see these tiny strings.
At first it seems strange that such a simple concept--replacing point particles with strings--can explain the rich diversity of particles and forces (which are created by the exchange of particles) in nature. The superstring theory, however, is so elegant and comprehensive that it is able to explain simply why there can be billions upon billions of different types of particles and substances in the universe, each with astonishingly diverse characteristics.
The superstring theory can produce a coherent and all-inclusive picture of nature similar to the way a violin string can be used to "unite" all the musical tones and rules of harmony. Historically, the laws of music were formulated only after thousands of years of trial-and-error investigation of different musical sounds. Today, these diverse rules can be derived easily from a single picture--that is, a string that can resonate with different frequencies, each one creating a separate tone of the musical scale. The tones created by the vibrating string, such as C or B flat, are not in themselves any more fundamental that any other tone. What is fundamental, however, is the fact that a single concept, vibrating strings, can explain the laws of harmony.
Knowing the physics of a violin string, therefore, gives us a comprehensive theory of musical tones and allows us to predict new harmonies and chords. Similarly, in the superstring theory, the fundamental forces and various particles found in nature are nothing more than different modes of vibrating strings. The gravitational interaction, for example, is caused by the lowest vibratory mode of a circular string (a loop). Higher excitations of the string create different forms of matter. From the point of view of the superstring theory, no force or particles i more fundamental than any other. All particles are just different vibratory resonances of vibrating strings. Thus, a single framework--the superstring theory--can in principle explain why the universe is populated with such a rich diversity of particles and atoms.
The answer to the ancient question "What is matter?" is simply that matter consists of particles that are different modes of vibration of the string, such as the note G or F. The "music" created by the string is matter itself.
...Over the last two thousand years, we gradually have realized that there are four fundamental forces: gravity, electromagnetism (light), and two types of nuclear forces, the weak and the strong. One of the great scientific puzzles of our universe, however, has been why these four forces seemed so different. For the past fifty years, physicists have grappled with the problem of uniting them into a coherent picture.