A time‐dependent centrality metric for disciplinary coauthorship graphs, the “Nobel number” for a discipline, is introduced. A researcher's Nobel number for a given discipline in a given year is defined as the researcher's average coauthorship distance to that discipline's Nobel laureates in that year. Plotting Nobel numbers over several decades provides a quantitative as well as visual indication of a researcher's proximity to the intuitive “center” of a discipline as defined by recognized scientific achievement. It is shown that the Nobel number distributions for physics of several researchers both within and outside of physics are surprisingly flat over the five‐decade span from 1951 to 2000. A model in which Nobel laureates are typically connected by short coauthorship paths both intergenerationally and between subdisciplines reproduces such flat Nobel number distributions.