"Gravity from strings: personal reminiscence on early developments." arXiv preprint arXiv:0901.0079 ."

“We have emphasized that there is a big conflict between quantum theory and general relativity, since it leads to ultraviolet difficulties. However, it does not mean that both frameworks are fundamentally contradictory to each other. In fact, at large distances, the situation is quite contrary. For an example, an old story in the famous debates between Einstein and Bohr shows that the quantum mechanical uncertainty relation ∆E ∆t ≥ h is consistent with the equivalence principle when ... applied to the measurement of weights in weak gravitational fields. Their mutual contradiction is manifested only at sufficiently short distances near the Planck length, where the quantum gravitational effects become of the same order as other nongravitational effects.”

“... when I was exposed to a short but remarkable preprint by Susskind giving a physical interpretation of the Veneziano formula in terms of vibrating strings , I was struck by the simplicity of the idea. My interest on dual models was further strengthened by reading the paper by Nambu , containing similar discussions. In particular, I was intrigued by the concept of ‘master field’ , which had been emphasized by Nambu. A little later I also came to be fascinated by the very attractive world-sheet picture of Fairlie and Nielsen .”

“... string theory ... introduces the fundamental unit of length, √α′ ≡ ls. The string length ls replaces the role of the Planck length in ordinary approaches to quantizing gravity within the framework of local field theory. In string theory, the gravitational interaction is built-in in a completely unified way with all other particle interactions. In the unit in which the 10 dimensional Newton constant and the light velocity are unity, the Planck constant h is related to the string length as h = gs2 ls8 where gs is the dimensionless string coupling given by the vacuum expectation value of the dilaton gs = eφ.”