But that picture has changed in the last few years, and we now believe that string theory can contain different, independent types of string, each of which can oscillate in many possible ways. Theorists initially thought there was only a single type of fundamental string that is responsible for all known particles. Because of the many ways in which strings can vibrate, a single string can give rise to many types of particle. Each and every particle corresponds to the vibrations of an underlying string, and the character of those vibrations determines the particle’s properties. String theory’s radical hypothesis is that particles arise from the resonant oscillation modes of strings. According to string theory, the yarn a cat plays with is made of atoms that are ultimately composed of the vibrations of strings. These are fundamental strings, which means that everything, including electrons and quarks, consists of their oscillations. These strings, unlike violin strings, say, are not made up of atoms which are in turn made up of electrons and nucleons which are in turn made up of quarks.

According to string theory, the most basic indivisible objects underlying all matter are strings-vibrating, one-dimensional loops or segments of energy. String theory’s view of the fundamental nature of matter differs significantly from that of traditional particle physics.

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The following is excerpted from Warped Passages by Lisa Randall.

Physics strings theory