Chapter Fifteen, Prospects Summary and Analysis

The major lesson physicists have learned in the past studies is how closely the laws of physics are related to symmetry. Part of the reason string theory is so attractive is that symmetry—including supersymmetry—are encompassed in its structure. In the context of string theory the symmetries are consequences, not ideas forced into the theory. Moving forward in string theory, physicists are focused on finding the principle of inevitability, or the essential underlying framework that makes the theory tick.

The fabric of spacetime is made of the vibrating strings, known as a coherent state of strings, though the strings themselves do not take part in the fabric unless they vibrate. If they do not, there is no notion of time or space—the string simply is. In M-theory, the zero-brane gives physicists an...