John Archibald Wheeler (July 9, 1911 – April 13, 2008) was an Americantheoretical physicist. He was largely responsible for reviving interest ingeneral relativity in the United States afterWorld War II. Wheeler also worked withNiels Bohr to explain the basic principles ofnuclear fission. Together withGregory Breit, Wheeler developed the concept of theBreit–Wheeler process. He is best known for popularizing the term "black hole"[1] for objects with gravitational collapse already predicted during the early 20th century, for inventing the terms "quantum foam", "neutron moderator", "wormhole" and "it from bit",[2] and for hypothesizing the "one-electron universe".Stephen Hawking called Wheeler the "hero of the black hole story".[3]
At 21, Wheeler earned his doctorate atJohns Hopkins University under the supervision ofKarl Herzfeld. He studied under Breit and Bohr on aNational Research Council fellowship. In 1939 he collaborated with Bohr on a series of papers using theliquid drop model to explain the mechanism of fission. During World War II, he worked with theManhattan Project'sMetallurgical Laboratory in Chicago, where he helped designnuclear reactors, and then at theHanford Site inRichland, Washington, where he helpedDuPont build them. He returned to Princeton after the war but returned to government service to help design and build thehydrogen bomb in the early 1950s. He andEdward Teller were the main civilian proponents of thermonuclear weapons.[4]
For most of his career, Wheeler was aprofessor of physics atPrinceton University, which he joined in 1938, remaining until 1976. At Princeton he supervised 46 PhD students, more than any other physics professor.
Wheeler left Princeton at the age of 65. He was appointed director of the Center for Theoretical Physics at theUniversity of Texas at Austin in 1976 and remained in the position until 1986, when he retired and became aprofessor emeritus.
Wheeler was born inJacksonville, Florida, on July 9, 1911, to librariansJoseph L. Wheeler and Mabel Archibald (Archie) Wheeler.[5] He was the oldest of four children. His brother Joseph earned aPhD fromBrown University and aMaster of Library Science fromColumbia University. His brother Robert earned a PhD ingeology fromHarvard University and worked as a geologist for oil companies and several colleges. His sister Mary studied library science at theUniversity of Denver and became a librarian.[6] They grew up inYoungstown, Ohio, but spent a year in 1921 to 1922 on a farm inBenson, Vermont, where Wheeler attended aone-room school. When they returned to Youngstown he attendedRayen High School.[7]
After graduating fromBaltimore City College high school in 1926,[8] Wheeler enteredJohns Hopkins University with a scholarship from the state ofMaryland.[9] He published his first scientific paper in 1930, as part of a summer job at theNational Bureau of Standards.[10] He earned his doctorate in 1933. His dissertation research work, carried out under the supervision ofKarl Herzfeld, was on the "Theory of the Dispersion and Absorption of Helium".[11] He received aNational Research Council fellowship, which he used to study underGregory Breit atNew York University in 1933 and 1934,[12] and then inCopenhagen underNiels Bohr in 1934 and 1935.[13] In a 1934 paper, Breit and Wheeler introduced theBreit–Wheeler process, a mechanism by whichphotons can be potentiallytransformed into matter in the form ofelectron–positron pairs.[9][14]
TheUniversity of North Carolina at Chapel Hill made Wheeler an associate professor in 1937, but he wanted to be able to work more closely with experts in particle physics.[15] He turned down an offer in 1938 of an associate professorship at Johns Hopkins University in favor of an assistant professorship atPrinceton University. Although it was a lesser position, he felt that Princeton, which was building up its physics department, was a better career choice.[16] He remained a member of its faculty until 1976.[17]
In his 1937 paper "On the Mathematical Description of Light Nuclei by the Method of Resonating Group Structure", Wheeler introduced theS-matrix—short for scattering matrix—"a unitary matrix of coefficients connecting the asymptotic behavior of an arbitrary particular solution [of the integral equations] with that of solutions of a standard form".[18][19] Wheeler did not pursue this idea, but in the 1940sWerner Heisenberg developed the idea of the S-matrix into an important tool in elementaryparticle physics.[18]
In 1938 Wheeler joinedEdward Teller in examining Bohr'sliquid drop model of theatomic nucleus;[20] they presented their results at a meeting of theAmerican Physical Society in New York. Wheeler's Chapel Hill graduate studentKatharine Way also presented a paper, which she followed up in a subsequent article, detailing how the liquid drop model was unstable under certain conditions. Due to a limitation of the liquid drop model, they all missed the opportunity to predictnuclear fission.[21][22] In 1939, Bohr brought the news ofLise Meitner's andOtto Frisch's discovery of fission to America. Bohr toldLeon Rosenfeld, who informed Wheeler.[16]
Bohr and Wheeler set to work applying the liquid drop model to explain the mechanism of nuclear fission.[23] As the experimental physicists studied fission, they uncovered puzzling results.George Placzek asked Bohr whyuranium seemed to fission with both very fast and very slowneutrons. Walking to a meeting with Wheeler, Bohr had an insight that fission at low energies was due to theuranium-235isotope, while at high energies it was mainly due to the far more abundanturanium-238 isotope.[24] They co-wrote two more papers on fission.[25][26] Their first paper appeared inPhysical Review on September 1, 1939, the dayGermany invaded Poland, startingWorld War II.[27]
Considering the notion that positrons were electrons traveling backward in time, in 1940 Wheeler conceived hisone-electron universe postulate: that there was in fact only one electron, bouncing back and forth in time. His graduate studentRichard Feynman found this hard to believe, but the idea that positrons were electrons traveling backward in time intrigued him, and Feynman incorporated the notion of the reversibility of time in hisFeynman diagrams.[28]
Soon after the Japanesebombing of Pearl Harbor brought the U.S. into World War II, Wheeler accepted a request fromArthur Compton to join theManhattan Project'sMetallurgical Laboratory at theUniversity of Chicago. He moved there in January 1942,[27] joiningEugene Wigner's group, which was studyingnuclear reactor design.[29] He co-wrote a paper withRobert F. Christy on "Chain Reaction of Pure Fissionable Materials in Solution", which was important in theplutonium purification process.[30] It was declassified in December 1955.[31] He gave theneutron moderator its name, replacingEnrico Fermi's term, "slower downer".[32][33]
After theUnited States Army Corps of Engineers took over the Manhattan Project, it gaveDuPont responsibility for the detailed design and construction of the reactors.[34] Wheeler became part of DuPont's design staff.[35] He worked closely with its engineers, commuting between Chicago andWilmington, Delaware, where DuPont had its headquarters. He moved his family to Wilmington in March 1943.[36] DuPont's task was to build not just nuclear reactors, but an entire plutonium production complex at theHanford Site inWashington.[37] As work progressed, Wheeler relocated his family again in July 1944, toRichland, Washington, where he worked in the scientific buildings known as the300 area.[30][36]
Even before the Hanford Site started up theB Reactor, the first of its three reactors, on September 15, 1944, Wheeler had been concerned that somenuclear fission products might benuclear poisons, the accumulation of which would impede the ongoingnuclear chain reaction by absorbing many of thethermal neutrons needed to continue a chain reaction.[38] In an April 1942 report, he predicted that this would reduce the reactivity by less than one percent so long as no fission product had aneutron capturecross section of more than 100,000barns.[39] After the reactor unexpectedly shut down, and then just as unexpectedly restarted about 15 hours later, he suspectediodine-135, with ahalf-life of 6.6 hours, and its daughter product,xenon-135, which has a half-life of 9.2 hours. Xenon-135 turned out to have a neutron capture cross-section of well over two million barns. The problem was corrected by adding additional fuel slugs to burn out the poison.[40]
Wheeler had a personal reason for working on the Manhattan Project. His brother Joe, fighting in Italy, sent him a postcard with a simple message: "Hurry up".[41] It was already too late: Joe was killed in October 1944. "Here we were", Wheeler later wrote, "so close to creating a nuclear weapon to end the war. I couldn't stop thinking then, and haven't stopped thinking since, that the war could have been over in October 1944."[40] Joe left a widow and baby daughter, Mary Jo, who later married physicistJames Hartle.[42]
In August 1945 Wheeler and his family returned to Princeton, where he resumed his academic career.[43] Working with Feynman, he explored the possibility of physics with particles, but not fields, and carried out theoretical studies of themuon withJayme Tiomno,[44] resulting in a series of papers on the topic,[45][46] including a 1949 paper in which Tiomno and Wheeler introduced the "Tiomno Triangle", which related different forms of radioactive decay.[47] He also suggested the use of muons as a nuclear probe. This paper, written and privately circulated in 1949 but not published until 1953,[48] resulted in a series of measurements of the Chang radiation emitted by muons. Muons are a component ofcosmic rays, and Wheeler became the founder and first director of Princeton's Cosmic Rays Laboratory, which received a grant of $375,000 from theOffice of Naval Research in 1948.[49] Wheeler received aGuggenheim Fellowship in 1946,[50] which allowed him to spend the 1949–50 academic year in Paris.[51]
The 1949 detonation ofJoe-1 by theSoviet Union prompted an all-out effort by the United States, led by Teller, to develop the more powerfulhydrogen bomb in response.Henry D. Smyth, Wheeler's department head at Princeton, asked him to join the effort. Most physicists were, like Wheeler, trying to reestablish careers interrupted by the war and reluctant to face more disruption. Others had moral objections.[52] Those who agreed to participate includedEmil Konopinski,Marshall Rosenbluth,Lothar Nordheim, andCharles Critchfield, but there was also now a body of experienced weapons physicists at theLos Alamos Laboratory, led byNorris Bradbury.[53][54] Wheeler agreed to go to Los Alamos after a conversation with Bohr.[52] Two of his graduate students from Princeton,Ken Ford andJohn Toll, joined him there.[55]
At Los Alamos, Wheeler and his family moved into the house on "Bathtub Row" thatRobert Oppenheimer and his family had occupied during the war.[56] In 1950 there was no practical design for a hydrogen bomb. Calculations byStanisław Ulam and others showed that Teller's "Classical Super" would not work. Teller and Wheeler created a new design known as "Alarm Clock", but it was not a true thermonuclear weapon. Not until January 1951 did Ulamcome up with a workable design.[57]
In 1951 Wheeler obtained Bradbury's permission to set up a branch office of the Los Alamos laboratory at Princeton, known asProject Matterhorn, which had two parts. Matterhorn S (forstellarator, another name coined by Wheeler), under Lyman Spitzer, investigatednuclear fusion as a power source. Matterhorn B (for bomb), under Wheeler, did nuclear weapons research. Senior scientists remained uninterested and aloof from the project, so he staffed it with young graduate and postdoctoral students.[58] Matterhorn B's efforts were crowned by the success of theIvy Mike nuclear test atEnewetak Atoll in the Pacific, on November 1, 1952,[59][58] which Wheeler witnessed. The yield of the Ivy Mike "Sausage" device was reckoned at 10.4megatons of TNT (44 PJ), about 30 percent higher than Matterhorn B had estimated.[60]
In January 1953 Wheeler was involved in a security breach when he lost a highly classified paper onlithium-6 and the hydrogen bomb design during an overnight train trip.[61][62] This resulted in an official reprimand.[63]
Matterhorn B was discontinued, but Matterhorn S endures as thePrinceton Plasma Physics Laboratory.[58]
After concluding his Matterhorn Project work, Wheeler resumed his academic career. In a 1955 paper, he theoretically investigated thegeon, anelectromagnetic orgravitational wave held together in a confined region by the attraction of its ownfield. He coined the name as a contraction of "gravitational electromagnetic entity".[64] He found that the smallest geon was atoroid the size of the Sun, but millions of times heavier. He later showed that geons are unstable, and would quickly self destruct if they were ever to form.[65]
During the 1950s, Wheeler formulatedgeometrodynamics, a program of physical and ontological reduction of every physical phenomenon, such asgravitation andelectromagnetism, to the geometrical properties of a curved space-time. His research on the subject was published in 1957 and 1961.[66][67] Wheeler envisaged the fabric of the universe as a chaotic subatomic realm ofquantum fluctuations, which he called "quantum foam".[64][68]
General relativity had been considered a less respectable field of physics, being detached from experiment. Wheeler was a key figure in its revival, leading the school at Princeton, whileDennis William Sciama andYakov Borisovich Zel'dovich developed the subject atCambridge University and theUniversity of Moscow, respectively. Wheeler and his students made substantial contributions to the field during theGolden Age of General Relativity.[69]
While working on mathematical extensions to Einstein's general relativity in 1957, Wheeler introduced the concept and wordwormhole to describe hypothetical "tunnels" inspace-time. Bohr asked whether they were stable and further research by Wheeler determined that they are not.[70][71] His work in general relativity included the theory of gravitational collapse. He used the termblack hole in 1967 during a talk he gave at theNASA Goddard Institute of Space Studies (GISS),[72] although the term had been used earlier in the decade.[a] Wheeler said the term was suggested to him during a lecture when a member of the audience was tired of hearing Wheeler say "gravitationally completely collapsed object". Wheeler was also a pioneer in the field ofquantum gravity due to his development, withBryce DeWitt, of theWheeler–DeWitt equation in 1967.[74] Stephen Hawking later described Wheeler and DeWitt's work as the equation governing the "wave function of the Universe".[75]
Wheeler left Princeton in 1976 at age 65. He was appointed director of the Center for Theoretical Physics at theUniversity of Texas at Austin in 1976 and remained in the position until 1986, when he retired[17] and became aprofessor emeritus.[76] Misner, Thorne andWojciech Zurek, all former students of Wheeler, wrote:
Looking back on Wheeler's 10 years at Texas, many quantum information scientists now regard him, along with IBM'sRolf Landauer, as a grandfather of their field. That, however, was not because Wheeler produced seminal research papers on quantum information. He did not—with one major exception, his delayed-choice experiment. Rather, his role was to inspire by asking deep questions from a radical conservative viewpoint and, through his questions, to stimulate others' research and discovery.[77]
Wheeler's delayed-choice experiment describes a family ofthought experiments inquantum physics that he proposed, with the most prominent of them appearing in 1978 and 1984. These experiments seek to discover whether light somehow "senses" the experimental apparatus that it travels through in thedouble-slit experiment, adjusting its behavior to fit by assuming an appropriate determinate state, or whether it remains in an indeterminate state, neither wave nor particle, and responds to the "questions" the experimental arrangements ask of it in either a wave-consistent manner or a particle-consistent manner.[78]
Wheeler's graduate students includedJacob Bekenstein,Hugh Everett,Richard Feynman, Peter Putnam,[79] David Hill, Bei-Lok Hu,John R. Klauder,Charles Misner,Kip Thorne,William Unruh,Robert M. Wald,Katharine Way, andArthur Wightman.[11][80] Wheeler gave teaching high priority, and continued to teachfreshman andsophomore physics, saying that young minds were the most important. At Princeton he supervised 46 PhDs, more than any other physics professor.[81] Wheeler wrote a supportive review article to help Hugh Everett's work, wrote to and met withNiels Bohr in Copenhagen seeking his approval of Everett's approach, and continued to advocate for Everett even after Bohr's rejection.[82][83] With Kent Harrison,Kip Thorne, and Masami Wakano, Wheeler wroteGravitation Theory and Gravitational Collapse (1965). This led to the voluminous general relativity textbookGravitation (1973), co-written with Misner and Thorne. Its timely appearance during the golden age of general relativity and its comprehensiveness made it an influential relativity textbook for a generation.[84] Wheeler andEdwin F. Taylor wroteSpacetime Physics (1966) andScouting Black Holes (1996).
Alluding to Wheeler's "mass without mass", thefestschrift honoring his 60th birthday was titledMagic Without Magic: John Archibald Wheeler: A Collection of Essays in Honor of his Sixtieth Birthday (1972). His writing style could also attract parodies, including one by "John Archibald Wyler" that was affectionately published by a relativity journal.[85][86]
Wheeler speculated that reality is created by observers in the universe. "How does something arise from nothing?", he asked about the existence of space and time.[87][88][79] He also coined the term "Participatory Anthropic Principle" (PAP), a version of a stronganthropic principle.[89]
In 1990, Wheeler suggested that information is fundamental to the physics of the universe. According to this "it from bit" doctrine, all things physical are information-theoretic in origin:
Wheeler:It from bit. Otherwise put, everyit—every particle, every field of force, even the space-time continuum itself—derives its function, its meaning, its very existence entirely—even if in some contexts indirectly—from the apparatus-elicited answers to yes-or-no questions, binary choices, bits.It from bit symbolizes the idea that every item of the physical world has at bottom—at a very deep bottom, in most instances—an immaterial source and explanation; that which we call reality arises in the last analysis from the posing of yes–no questions and the registering of equipment-evoked responses; in short, that all things physical are information-theoretic in origin and that this is aparticipatory universe.[90]
In developing the participatory anthropic principle, aninterpretation of quantum mechanics, Wheeler used a variant onTwenty Questions, called Negative Twenty Questions, to show how the questions we choose to ask about the universe may dictate the answers we get. In this variant, the respondent does not choose or decide upon any particular or definite object beforehand, but only on a pattern of "Yes" or "No" answers. This variant requires the respondent to provide a consistent set of answers to successive questions, so that each answer can be viewed as logically compatible with all the previous ones. In this way, successive questions narrow the options until the questioner settles upon a definite object. Wheeler's theory was that, in an analogous manner, consciousness may play some role in bringing the universe into existence.[91]
From a transcript of a radio interview on "The Anthropic Universe":
Wheeler: We are participators in bringing into being not only the near and here but the far away and long ago. We are in this sense, participators in bringing about something of the universe in the distant past and if we have one explanation for what's happening in the distant past why should we need more?
Martin Redfern: Many don't agree with John Wheeler, but if he's right then we and presumably other conscious observers throughout the universe, are the creators—or at least the minds that make the universe manifest.[92]
In 1979, Wheeler spoke to theAmerican Association for the Advancement of Science (AAAS), asking it to expelparapsychology, which had been admitted ten years earlier atMargaret Mead's request. He called it apseudoscience,[93] saying he did not oppose earnest research into the questions, but 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.[94] In the question-and-answer period following his presentation "Not consciousness, but the distinction between the probe and the probed, as central to the elemental quantum act of observation", Wheeler incorrectly said thatJ. B. Rhine had committed fraud as a student, for which he apologized in a subsequent letter to the journalScience.[95] His request was turned down and theParapsychological Association remained a member of the AAAS.[94]
For 72 years, Wheeler was married to Janette Hegner, a teacher and social worker. They became engaged on their third date, but agreed to defer marriage until he returned from Europe. They were married on June 10, 1935, five days after his return.[96] Employment was difficult to find during theGreat Depression.Arthur Ruark offered Wheeler a position as anassistant professor at theUniversity of North Carolina at Chapel Hill, at an annual salary of $2,300, which was less than the $2,400 Janette was offered to teach at the Rye Country Day School.[97][16] They had three children.[17]
Wheeler and Hegner were founding members of theUnitarian Church of Princeton, and she initiated the Friends of thePrinceton Public Library.[98] In their later years, Hegner accompanied him on sabbaticals in France, Los Alamos, New Mexico, the Netherlands, and Japan.[98] Hegner died in October 2007 at the age of 96.[99][100]
Wheeler won numerous prizes and awards, including the Golden Plate Award of theAmerican Academy of Achievement in 1966,[101] theEnrico Fermi Award in 1968, theFranklin Medal in 1969, theEinstein Prize in 1969, theNational Medal of Science in 1971, theNiels Bohr International Gold Medal in 1982, theOersted Medal in 1983, theJ. Robert Oppenheimer Memorial Prize in 1984, and theWolf Foundation Prize in 1997.[76] He was a member of theAmerican Philosophical Society, theRoyal Academy, theAccademia Nazionale dei Lincei, and theCentury Association. He received honorary degrees from 18 different institutions. In 2001, Princeton used a $3 million gift to establish the John Archibald Wheeler/Battelle Professorship in Physics.[17] After his death, the University of Texas named the John A. Wheeler Lecture Hall in his honor.[76]
On April 13, 2008, Wheeler died ofpneumonia at the age of 96 inHightstown, New Jersey.[1]
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