Szerkesztő:Whami/John Archibald Wheeler

John Archibald Wheeler (1911. július 9. - 2008. április 13.) vezető amerikai elméleti fizikus volt. Mint Einstein egyik későbbi munkatársa, megpróbálta megvalósítani Einstein látomását, az egyesített térelméletet. Tőle származik a fekete lyuk és a féregjárat kifejezés, valamint az "it from bit" mondás is.

Élete

Az Egyesült Államok Florida államában, Jacksonville városban született. 1926-ban végzi el a Baltimore City College középiskolát, majd 1933-ban a John Hopkins Egyetemen doktorál. Disszertációját Karl Herzfeld felügyelete alatt készíti, témája a hélium abszorpciós és diszperziós tulajdonságainak elmélete.

1938-tól 1936-ig a fizika professzora a Princeton Egyetemen. 1976-tól 1986-ig az austini Texas Egyetem Elméleti Fizika Intézetének igazgatója. Igen nagy figyelmet fordított az oktatásra: miután híres lett sem hagyta abba az oktatást és előadásokat tartott alsóbb éves hallgatóknak, mivel szerinte a legfontosabbak mindíg a fiatal elmék. Doktori témavezetője volt a később Nobel-díjas Richard Feynmannak, a relativitás elméletében kitűnő Kip Thornenak vagy a kvantummechanika sokvilág-értelmezését kidolgozó Hugh Everettnek.

Wheeler számos fontos eredménnyel egészítette ki az elméleti fizikát. 1937-ben bevezette az S-mátrixot, mely a részecskefizika nélkülözhetetlen szközévé vált. Niels Bohrral és Enrico Fermivel együtt atommaghasadás elméletének úttörői. 1939-ben Bohrral kidolgozzák az atommag cseppmodelljét és azt a maghasadás folyamatára alkalmazzák.

A II. Viláőghűáború alatt több másvezető fizikussal együtt megszakítja akadémiai karrierjét, hogy csatlakozzon az Manhattan-tervhez, melynek célja az amerikai atombomba kifejlesztése volt. Wheeler Hanfordban kapott feladatot, ahol reaktorokat építettek, hogy a bomba számára plutóniumot állítsanak elő. 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.[2] He went on to work on the development of the American hydrogen bomb under Project Matterhorn.

After concluding his Matterhorn 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. Simulated view of a black hole in front of the Milky Way. Simulated view of a black hole in front of the Milky Way.

His work in general relativity included the theory of gravitational collapse; he coined the term black hole in 1967 during a talk at the NASA Goddard Institute of Space Studies (GISS).[3] 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 (Gardner 1981:185ff). 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"[4]: