He was a professor of physics at Princeton University from 1938 until 1976 and the director of the Center for Theoretical Physics at the University of Texas at Austin from 1976 to 1986. At the time of his death, he had returned to Princeton as a professor emeritus. Professor Wheeler's graduate students include Richard Feynman, Kip Thorne, and Hugh Everett. Unlike some scholars, he gave a high priority to teaching. Even after he had achieved fame, he continued to teach freshman and sophomore physics, saying that the young minds were the most important.
Wheeler made important contributions to theoretical physics. In 1937, he introduced the S-matrix, which became an indispensable tool in particle physics. He was a pioneer in the theory of nuclear fission, along with Niels Bohr and Enrico Fermi. In 1939, he collaborated with Bohr on the liquid drop model of nuclear fission.
Together with many other leading physicists, during World War II, Wheeler interrupted his academic career to participate in the development of the U.S. atomic bomb under the Manhattan Project at the Hanford site, where reactors were constructed to produce the chemical element plutonium for atomic bombs. Even before the Hanford site started up the B-Pile (the first of three reactors), he had anticipated that the accumulation of "fission product poisons" would eventually impede the ongoing nuclear chain reaction by absorbing neutrons, and he correctly deduced (by calculating the half-life decay rates) that an isotope of xenon (Xe135) would be most responsible. He went on to work on the development of the American hydrogen bomb under Project Matterhorn.
After concluding his Manhattan Project work, Wheeler returned to Princeton to resume his academic career. In 1957, while working on extensions to general relativity, he introduced the word wormhole to describe hypothetical tunnels in space-time.
In the 1950s, he formulated geometrodynamics, a program of physical and ontological reduction of every physical phenomenon, such as gravitation and electromagnetism, to the geometrical properties of a curved space-time. Aiming at a systematical identification of matter with space, geometrodynamics was often characterized as a continuation of the philosophy of nature as conceived by Descartes and Spinoza. Wheeler's geometrodynamics, however, failed to explain some important physical phenomena, such as the existence of fermions (electrons, muons, etc.) or that of gravitational singularities. Wheeler therefore abandoned this theory as somewhat fruitless in the early 1970s.
For a few decades, general relativity had not been considered a very respectable field of physics, being detached from experiment. Wheeler was a key figure in the revival of the subject, leading the school at Princeton, whilst Sciama and Zel'dovich developed the subject in Cambridge and Moscow. The work of Wheeler and his students contributed greatly to the golden age of general relativity.
His work in general relativity included the theory of gravitational collapse. The term black hole was coined in 1967 during a talk he gave at the NASA Goddard Institute of Space Studies (GISS). He was also a pioneer in the field of quantum gravity with his development (with Bryce DeWitt) of the Wheeler-DeWitt equation or, as he called it, the "wave function of the Universe."
Recognizing Wheeler's colorful way with words, characterized by such confections as "mass without mass", the festschrift honoring his 60th birthday was fittingly entitled Magic Without Magic: John Archibald Wheeler: A collection of essays in honor of his sixtieth birthday, Ed: John R. Klauder, (W. H. Freeman, 1972, ISBN 0-7167-0337-8).
John Wheeler was the driving force behind the voluminous general relativity textbook Gravitation, co-written with Charles W. Misner and Kip Thorne. Its timely appearance during the golden age of general relativity and its comprehensiveness made it the most influential relativity textbook for a generation.
In 1979, Wheeler spoke to the American Association for the Advancement of Science (AAAS), asking it to expel parapsychology, which had been admitted ten years earlier at the request of Margaret Mead. He called it a pseudoscience , saying he didn't oppose earnest research into the questions, but he thought the "air of legitimacy" of being an AAAS-Affiliate should be reserved until convincing tests of at least a few so-called psi effects could be demonstrated. His request was turned down, and the Parapsychological Association remained a member of the AAAS.
Wheeler was awarded the Wolf Prize in Physics in 1997.
Wheeler has speculated that the laws of physics may be evolving in a manner analogous to evolution by natural selection in biology. "How does something arise from nothing?", he asks about the existence of space and time (Princeton Physics News, 2006). He also coined the term "Participatory Anthropic Principle" (PAP), a version of a Strong Anthropic Principle. From a transcript of a radio interview on "The anthropic universe: