In the last forty years, physicists have proposed objects far smaller than quarks, called “strings.” Instead of being point particles, like electrons, strings are extremely tiny one-dimensional “strings” of energy. Their sizes would be the Planck length, where gravity and quantum physics are joined. (See the earlier chapter “Between Nothingness and Infinity.”) An important property of strings is that they occupy a space of nine or ten dimensions, instead of the familiar three.
