Complex sentence: He earned a Ph.D in physics at Caltech in 1971, and went on to become one of the world's foremost experts on the Big Bang theory and an early proponent of the theory of dark matter.
Split into simpler sentences: He earned a Ph.D in physics at Caltech in 1971, and went on to become one of the world's foremost experts on the Big Bang theory. He was an early proponent of the theory of dark matter.