It is very possible that a proper understanding of string theory will — Edward Witten

"He never does calculations except in his mind. I will fill pages with calculations before I understand what Im doing. But Edward will sit down only to calculate a minus sign, or a factor of two."

"Work by Strominger and Witten showed that the masses of the particles in each family depend upon... the way in which the boundaries of the various multidimensional holes in the Calabi-Yau shape intersect and overlap with one another. ...as strings vibrate through the extra curled-up dimensions, the precise arrangement of the various holes and the way in which the Calabi-Yau shape folds around them has a direct impact on the possible resonant patterns of vibration. ...as with the number of families, string theory can provide us with a framework for answering questions—such as why the electron and other particles have the masses they do—on which previous theories are completely silent. ...carrying through with such calculations requires that we know which Calabi-Yau space to take for the extra dimensions."

"Much as Kaluza found that a universe with five spacetime dimensions provided a framework for unifying electromagnetism and gravity, and much as string theorists found that a universe with ten spacetime dimensions provided a framework for unifying quantum mechanics and general relativity, Witten found that a universe with eleven spacetime dimensions provided a framework for unifying all string theories."

"Most people who havent been trained in physics probably think of what physicists do as a question of incredibly complicated calculations, but thats not really the essence of it. The essence of it is that physics is about concepts, wanting to understand the concepts, the principles by which the world works."

"My stay was nearly over when one day Ed Witten said to me, "I just learnt a new way to find exact S-matrices in two dimensions invented by Zamolodchikov and I want to extend the ideas to supersymmetric models. You are the S-matrix expert, arent you? Why dont we work together?" I was delighted. All my years of training in Berkeley gave me a tremendous advantage over Ed—for an entire week."

"A crucial observation, central to the second superstring revolution initiated by Witten and others in 1995, is that string theory actually includes ingredients with a variety of different dimensions: two-dimensional Frisbee-like constituents, three-dimensional blob-like constituents, and even more exotic possibilities to boot."