Physics is becoming so unbelievably complex that it is taking longer and longer to train a physicist. It takes so long to train a physicist to the place where he understands the nature of physical problems that he is already too old to solve them.
Source: In Isaac Asimov's Book of Science and Nature Quotations, ed. Jason Shulman & Isaac Asimov, 1988.
-- Eugene Wigner, (Nov 17 1902-1995), Hungarian-US physicist; He was the joint winner, with Jensen and Mayer, of the Nobel Prize, 1963, for extensive work on quantum mechanics.