Abstract
Over the last 50 years, three different superstring formalisms have been developed. In 1971, Ramond and Neveu and Schwarz built a formalism with manifest Lorentz invariance but hidden spacetime supersymmetry. In 1981, Green and Schwarz built a formalism where supersymmetry is manifest but Lorentz invariance is hidden. And over the last 20 years, a third formalism involving pure spinors wa…