"In an enterprise such as the building of the atomic bomb the difference between ideas, hopes, suggestions and theoretical calculations, and solid numbers based on measurement, is paramount. All the committees, the politicking and the plans would have come to naught if a few unpredictable nuclear cross sections had been different from what they are by a factor of two."
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Source : Epigraph by Emilio G. Segre in Richard Rhodes' book "The Making of the Atomic Bomb" (p. 8), 1986.