Physicists learned rather unexpectedly, beginning in the early 1970s, that the problem of quantum gravity could be overcome by introducing a new sort of fuzziness. One replaces “point particles” by “strings”. Of course, the point particles and strings must both be treated quantum mechanically. Quantum effects are proportional to Planck’s constant , and stringy effects are proportional to a new constant (equal to approximately ) that determines the size of strings.

— Edward Witten

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2010.05.03 Monday ACHK