Initial calculations of an evolving r -process, showing the evolution of calculated results with time, also suggested that the r -process abundances are a superposition of differing neutron fluences. Small fluence produces the first r -process abundance peak near atomic weight A = 130 but no actinides, whereas large fluence produces the actinides uranium and thorium but no longer contains the A = 130 abundance peak. These processes occur in a fraction of a second to a few seconds, depending on details. Hundreds of subsequent papers published have utilized this time-dependent approach. The only modern nearby supernova, 1987A, has not revealed r -process enrichments. Modern thinking is that the r -process yield may be ejected from some supernovae but swallowed up in others as part of the residual neutron star or black hole.