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Julian Seymour Schwinger (; February 12, 1918 – July 16, 1994) was a
Nobel Prize The Nobel Prizes ( ; ; ) are awards administered by the Nobel Foundation and granted in accordance with the principle of "for the greatest benefit to humankind". The prizes were first awarded in 1901, marking the fifth anniversary of Alfred N ...
-winning American
theoretical physicist Theoretical physics is a branch of physics that employs mathematical models and abstractions of physical objects and systems to rationalize, explain, and predict natural phenomena. This is in contrast to experimental physics, which uses experi ...
. He is best known for his work on
quantum electrodynamics In particle physics, quantum electrodynamics (QED) is the Theory of relativity, relativistic quantum field theory of electrodynamics. In essence, it describes how light and matter interact and is the first theory where full agreement between quant ...
(QED), in particular for developing a relativistically invariant
perturbation theory In mathematics and applied mathematics, perturbation theory comprises methods for finding an approximate solution to a problem, by starting from the exact solution of a related, simpler problem. A critical feature of the technique is a middle ...
, and for renormalizing QED to one loop order. Schwinger was a physics professor at several universities. Schwinger is recognized as an important physicist, responsible for much of modern quantum field theory, including a variational approach, and the equations of motion for quantum fields. He developed the first
electroweak In particle physics, the electroweak interaction or electroweak force is the unified description of two of the fundamental interactions of nature: electromagnetism (electromagnetic interaction) and the weak interaction. Although these two forc ...
model, and the first example of confinement in 1+1 dimensions. He is responsible for the theory of multiple neutrinos, Schwinger terms, and the theory of the spin-3/2 field.


Biography


Early life and career

Julian Seymour Schwinger was born in New York City, to
Ashkenazi Jewish Ashkenazi Jews ( ; also known as Ashkenazic Jews or Ashkenazim) form a distinct subgroup of the Jewish diaspora, that Ethnogenesis, emerged in the Holy Roman Empire around the end of the first millennium Common era, CE. They traditionally spe ...
parents, Belle (née Rosenfeld) and Benjamin Schwinger, a garment manufacturer, who had emigrated from
Poland Poland, officially the Republic of Poland, is a country in Central Europe. It extends from the Baltic Sea in the north to the Sudetes and Carpathian Mountains in the south, bordered by Lithuania and Russia to the northeast, Belarus and Ukrai ...
to the United States. Both his father and his mother's parents were prosperous clothing manufacturers, although the family business declined after the Wall Street Crash of 1929. The family followed the
Orthodox Jewish Orthodox Judaism is a collective term for the traditionalist branches of contemporary Judaism. Theologically, it is chiefly defined by regarding the Torah, both Written and Oral, as literally revealed by God on Mount Sinai and faithfully tra ...
tradition. Julian's older brother Harold Schwinger was born in 1911, seven years before Julian who was born in 1918. Schwinger was a precocious student. He attended the
Townsend Harris High School Townsend Harris High School (THHS; often also shortened to Townsend Harris or simply Townsend) is a public high school for the humanities in the New York City borough of Queens. It is located on the campus of Queens College, a public college p ...
from 1932 to 1934, a highly regarded high school for gifted students at the time. During high school, Julian had already started reading ''
Physical Review ''Physical Review'' is a peer-reviewed scientific journal. The journal was established in 1893 by Edward Nichols. It publishes original research as well as scientific and literature reviews on all aspects of physics. It is published by the Ame ...
'' papers by authors such as
Paul Dirac Paul Adrien Maurice Dirac ( ; 8 August 1902 – 20 October 1984) was an English mathematician and Theoretical physics, theoretical physicist who is considered to be one of the founders of quantum mechanics. Dirac laid the foundations for bot ...
in the library of the
City College of New York The City College of the City University of New York (also known as the City College of New York, or simply City College or CCNY) is a Public university, public research university within the City University of New York (CUNY) system in New York ...
, in whose campus Townsend Harris was then located. In the fall of 1934, Schwinger entered the City College of New York as an undergraduate. CCNY automatically accepted all Townsend Harris graduates at the time, and both institutions offered free tuition. Due to his intense interest in physics and mathematics, Julian performed very well in those subjects despite often skipping classes and learning directly from books. On the other hand, his lack of interest for other topics such as English led to academic conflicts with teachers of those subjects. After Julian had joined CCNY, his brother Harold, who had previously graduated from CCNY, asked his ex-classmate Lloyd Motz to "get to know ulian. Lloyd was a CCNY physics instructor and Ph.D. candidate at
Columbia University Columbia University in the City of New York, commonly referred to as Columbia University, is a Private university, private Ivy League research university in New York City. Established in 1754 as King's College on the grounds of Trinity Churc ...
at the time. Lloyd made the acquaintance, and soon recognized Julian's talent. Noticing Schwinger's academic problems, Lloyd decided to ask
Isidor Isaac Rabi Israel Isidor Isaac Rabi (; ; July 29, 1898 – January 11, 1988) was an American nuclear physicist who received the Nobel Prize in Physics in 1944 for his discovery of nuclear magnetic resonance, which is used in magnetic resonance imaging. H ...
who he knew at Columbia for help. Rabi also immediately recognized Schwinger's capabilities on their first meeting, and then made arrangements to award Schwinger with a scholarship to study at Columbia. At first Julian's bad grades in some subjects at CCNY prevented the scholarship award. But Rabi persisted and showed an unpublished paper on
quantum electrodynamics In particle physics, quantum electrodynamics (QED) is the Theory of relativity, relativistic quantum field theory of electrodynamics. In essence, it describes how light and matter interact and is the first theory where full agreement between quant ...
written by Schwinger to
Hans Bethe Hans Albrecht Eduard Bethe (; ; July 2, 1906 – March 6, 2005) was a German-American physicist who made major contributions to nuclear physics, astrophysics, quantum electrodynamics and solid-state physics, and received the Nobel Prize in Physi ...
, who happened to be passing by New York. Bethe's approval of the paper and his reputation in that domain were then enough to secure the scholarship for Julian, who then transferred to Columbia. His academic situation at Columbia was much better than at CCNY. He was accepted into the
Phi Beta Kappa The Phi Beta Kappa Society () is the oldest academic honor society in the United States. It was founded in 1776 at the College of William & Mary in Virginia. Phi Beta Kappa aims to promote and advocate excellence in the liberal arts and sciences, ...
society and received his B.A. in 1936. During Schwinger's graduate studies, Rabi felt that it would be good for Julian to visit other institutions around the country, and Julian was awarded a travelling fellowship for the year 37/38 which he spent at working with Gregory Breit and
Eugene Wigner Eugene Paul Wigner (, ; November 17, 1902 – January 1, 1995) was a Hungarian-American theoretical physicist who also contributed to mathematical physics. He received the Nobel Prize in Physics in 1963 "for his contributions to the theory of th ...
. During this time, Schwinger, who previously had already had the habit of working until late at night, went further and made the day/night switch more complete, working at night and sleeping during the day, a habit he would carry throughout his career. Schwinger later commented that this switch was in part a way to retain greater intellectual independence and avoid being "dominated" by Breit and Wigner by simply reducing the duration of contact with them by working different hours. Schwinger obtained his PhD overseen by Rabi in 1939 at the age of 21. During the fall of 1939 Schwinger started working at the
University of California, Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California), is a Public university, public Land-grant university, land-grant research university in Berkeley, California, United States. Founded in 1868 and named after t ...
under
J. Robert Oppenheimer J. Robert Oppenheimer (born Julius Robert Oppenheimer ; April 22, 1904 – February 18, 1967) was an American theoretical physics, theoretical physicist who served as the director of the Manhattan Project's Los Alamos Laboratory during World ...
, where he stayed for two years as an NRC fellow.


Career

After having worked with Oppenheimer, Schwinger's first regular academic appointment was at
Purdue University Purdue University is a Public university#United States, public Land-grant university, land-grant research university in West Lafayette, Indiana, United States, and the flagship campus of the Purdue University system. The university was founded ...
in 1941. While on leave from Purdue, he worked at the MIT Radiation Laboratory instead of at the
Los Alamos National Laboratory Los Alamos National Laboratory (often shortened as Los Alamos and LANL) is one of the sixteen research and development Laboratory, laboratories of the United States Department of Energy National Laboratories, United States Department of Energy ...
during World War II. He provided theoretical support for the development of
radar Radar is a system that uses radio waves to determine the distance ('' ranging''), direction ( azimuth and elevation angles), and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track ...
. After the war, Schwinger left Purdue for
Harvard University Harvard University is a Private university, private Ivy League research university in Cambridge, Massachusetts, United States. Founded in 1636 and named for its first benefactor, the History of the Puritans in North America, Puritan clergyma ...
, where he taught from 1945 to 1974. In 1966 he became the Eugene Higgins professor of physics at Harvard. Schwinger developed an affinity for
Green's function In mathematics, a Green's function (or Green function) is the impulse response of an inhomogeneous linear differential operator defined on a domain with specified initial conditions or boundary conditions. This means that if L is a linear dif ...
s from his radar work, and he used these methods to formulate quantum field theory in terms of local Green's functions in a relativistically invariant way. This allowed him to calculate unambiguously the first corrections to the electron magnetic moment in quantum electrodynamics. Earlier non-covariant work had arrived at infinite answers, but the extra symmetry in his methods allowed Schwinger to isolate the correct finite corrections. Schwinger developed
renormalization Renormalization is a collection of techniques in quantum field theory, statistical field theory, and the theory of self-similar geometric structures, that is used to treat infinities arising in calculated quantities by altering values of the ...
, formulating
quantum electrodynamics In particle physics, quantum electrodynamics (QED) is the Theory of relativity, relativistic quantum field theory of electrodynamics. In essence, it describes how light and matter interact and is the first theory where full agreement between quant ...
unambiguously to one-loop order. In the same era, he introduced non-perturbative methods into quantum field theory, by calculating the rate at which
electron The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...
positron The positron or antielectron is the particle with an electric charge of +1''elementary charge, e'', a Spin (physics), spin of 1/2 (the same as the electron), and the same Electron rest mass, mass as an electron. It is the antiparticle (antimatt ...
pairs are created by tunneling in an electric field, a process now known as the "Schwinger effect." This effect could not be seen in any finite order in perturbation theory. Schwinger's foundational work on quantum field theory constructed the modern framework of field correlation functions and their
equations of motion In physics, equations of motion are equations that describe the behavior of a physical system in terms of its motion as a function of time. More specifically, the equations of motion describe the behavior of a physical system as a set of mathem ...
. His approach started with a quantum action and allowed bosons and fermions to be treated equally for the first time, using a differential form of Grassman integration. He gave elegant proofs for the spin-statistics theorem and the CPT theorem, and noted that the field algebra led to anomalous Schwinger terms in various classical identities, because of short distance singularities. These were foundational results in field theory, instrumental for the proper understanding of anomalies. In other notable early work, Rarita and Schwinger formulated the abstract Pauli and Fierz theory of the spin-3/2 field in a concrete form, as a vector of Dirac spinors, Rarita–Schwinger equation. In order for the spin-3/2 field to interact consistently, some form of
supersymmetry Supersymmetry is a Theory, theoretical framework in physics that suggests the existence of a symmetry between Particle physics, particles with integer Spin (physics), spin (''bosons'') and particles with half-integer spin (''fermions''). It propo ...
is required, and Schwinger later regretted that he had not followed up on this work far enough to discover supersymmetry. Schwinger discovered that
neutrino A neutrino ( ; denoted by the Greek letter ) is an elementary particle that interacts via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass is so small ('' -ino'') that i ...
s come in multiple varieties, one for the
electron The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...
and one for the
muon A muon ( ; from the Greek letter mu (μ) used to represent it) is an elementary particle similar to the electron, with an electric charge of −1 '' e'' and a spin of  ''ħ'', but with a much greater mass. It is classified as a ...
. Nowadays there are known to be three light neutrinos; the third is the partner of the tau lepton. In the 1960s, Schwinger formulated and analyzed what is now known as the Schwinger model, quantum electrodynamics in one space and one time dimension, the first example of a confining theory. He was also the first to suggest an electroweak gauge theory, an SU(2) gauge group spontaneously broken to electromagnetic U(1) at long distances. This was extended by his student
Sheldon Glashow Sheldon Lee Glashow (, ; born December 5, 1932) is a Nobel Prize-winning American theoretical physicist. He is the Metcalf Professor of Mathematics and Physics at Boston University, and a Eugene Higgins Professor of Physics, emeritus, at Harv ...
into the accepted pattern of electroweak unification. He attempted to formulate a theory of quantum electrodynamics with point magnetic monopoles, a program which met with limited success because monopoles are strongly interacting when the quantum of charge is small. Having supervised 73 doctoral dissertations, Schwinger is known as one of the most prolific graduate advisors in physics. Four of his students won Nobel prizes: Roy Glauber, Benjamin Roy Mottelson,
Sheldon Glashow Sheldon Lee Glashow (, ; born December 5, 1932) is a Nobel Prize-winning American theoretical physicist. He is the Metcalf Professor of Mathematics and Physics at Boston University, and a Eugene Higgins Professor of Physics, emeritus, at Harv ...
and Walter Kohn (in chemistry). Schwinger had a mixed relationship with his colleagues, because he always pursued independent research, different from mainstream fashion. In particular, Schwinger developed the source theory, a phenomenological theory for the physics of elementary particles, which is a predecessor of the modern
effective field theory In physics, an effective field theory is a type of approximation, or effective theory, for an underlying physical theory, such as a quantum field theory or a statistical mechanics model. An effective field theory includes the appropriate degrees ...
. It treats quantum fields as long-distance phenomena and uses auxiliary 'sources' that resemble currents in classical field theories. The source theory is a mathematically consistent field theory with clearly derived phenomenological results. The criticisms by his Harvard colleagues led Schwinger to leave the faculty in 1972 for
UCLA The University of California, Los Angeles (UCLA) is a public land-grant research university in Los Angeles, California, United States. Its academic roots were established in 1881 as a normal school then known as the southern branch of the C ...
. It is a story widely told that
Steven Weinberg Steven Weinberg (; May 3, 1933 – July 23, 2021) was an American theoretical physicist and Nobel laureate in physics for his contributions with Abdus Salam and Sheldon Glashow to the unification of the weak force and electromagnetic inter ...
, who inherited Schwinger's paneled office in Lyman Laboratory, there found a pair of old shoes, with the ''implied'' message, "think you can fill these?" Based on Schwinger's source theory, Weinberg set the underpinnings of the effective field theory, that is more appreciated among physicists. In spite of the shoes incident, Weinberg gave the credit to Schwinger for the inspiration. At UCLA, and for the rest of his career, Schwinger continued to develop the source theory and its various applications. After 1989 Schwinger took a keen interest in the non-mainstream research of
cold fusion Cold fusion is a hypothesized type of nuclear reaction that would occur at, or near, room temperature. It would contrast starkly with the nuclear fusion, "hot" fusion that is known to take place naturally within Main sequence, stars and artific ...
. He wrote eight theory papers about it. He resigned from the
American Physical Society The American Physical Society (APS) is a not-for-profit membership organization of professionals in physics and related disciplines, comprising nearly fifty divisions, sections, and other units. Its mission is the advancement and diffusion of ...
after their refusal to publish his papers. He felt that cold fusion research was being suppressed and academic freedom violated. He wrote, "The pressure for conformity is enormous. I have experienced it in editors' rejection of submitted papers, based on venomous criticism of anonymous referees. The replacement of impartial reviewing by censorship will be the death of science." In his last publications, Schwinger proposed a theory of
sonoluminescence Sonoluminescence is the emission of light from imploding bubbles in a liquid when excited by sound. Sonoluminescence was first discovered in 1934 at the University of Cologne. It occurs when a sound wave of sufficient intensity induces a gaseo ...
as a long-distance quantum radiative phenomenon associated not with atoms, but with fast-moving surfaces in the collapsing bubble, where there are discontinuities in the dielectric constant. The mechanism of sonoluminescence now supported by experiments focuses on superheated gas inside the bubble as the source of the light. Schwinger was jointly awarded the
Nobel Prize in Physics The Nobel Prize in Physics () is an annual award given by the Royal Swedish Academy of Sciences for those who have made the most outstanding contributions to mankind in the field of physics. It is one of the five Nobel Prizes established by the ...
in 1965 for his work on quantum electrodynamics (QED), along with
Richard Feynman Richard Phillips Feynman (; May 11, 1918 – February 15, 1988) was an American theoretical physicist. He is best known for his work in the path integral formulation of quantum mechanics, the theory of quantum electrodynamics, the physics of t ...
and Shin'ichirō Tomonaga. Schwinger's awards and honors were numerous even before his Nobel win. They include the first Albert Einstein Award (1951), the U.S.
National Medal of Science The National Medal of Science is an honor bestowed by the President of the United States to individuals in science and engineering who have made important contributions to the advancement of knowledge in the fields of behavioral science, behavior ...
(1964), honorary D.Sc. degrees from Purdue University (1961) and Harvard University (1962), and the Nature of Light Award of the U.S.
National Academy of Sciences The National Academy of Sciences (NAS) is a United States nonprofit, NGO, non-governmental organization. NAS is part of the National Academies of Sciences, Engineering, and Medicine, along with the National Academy of Engineering (NAE) and the ...
(1949). In 1987, Schwinger received the Golden Plate Award of the
American Academy of Achievement The American Academy of Achievement, colloquially known as the Academy of Achievement, is a nonprofit educational organization that recognizes some of the highest-achieving people in diverse fields and gives them the opportunity to meet one ano ...
.


Schwinger and Feynman

As a famous physicist, Schwinger was often compared to another legendary physicist of his generation,
Richard Feynman Richard Phillips Feynman (; May 11, 1918 – February 15, 1988) was an American theoretical physicist. He is best known for his work in the path integral formulation of quantum mechanics, the theory of quantum electrodynamics, the physics of t ...
. Schwinger was more formally inclined and favored symbolic manipulations in
quantum field theory In theoretical physics, quantum field theory (QFT) is a theoretical framework that combines Field theory (physics), field theory and the principle of relativity with ideas behind quantum mechanics. QFT is used in particle physics to construct phy ...
. He worked with local field operators, and found relations between them, and he felt that physicists should understand the algebra of local fields, no matter how paradoxical it was. By contrast, Feynman was more intuitive, believing that the physics could be extracted entirely from the
Feynman diagram In theoretical physics, a Feynman diagram is a pictorial representation of the mathematical expressions describing the behavior and interaction of subatomic particles. The scheme is named after American physicist Richard Feynman, who introduced ...
s, which gave a particle picture. Schwinger commented on Feynman diagrams in the following way, Schwinger disliked Feynman diagrams because he felt that they made the student focus on the particles and forget about local fields, which in his view inhibited understanding. He went so far as to ban them altogether from his class, although he understood them perfectly well. The true difference is however deeper, and it was expressed by Schwinger in the following passage, Despite sharing the Nobel Prize, Schwinger and Feynman had a different approach to quantum electrodynamics and to quantum field theory in general. Feynman used a regulator, while Schwinger was able to formally renormalize to one loop without an explicit regulator. Schwinger believed in the formalism of local fields, while Feynman had faith in the particle paths. They followed each other's work closely, and each respected the other. On Feynman's death, Schwinger described him as


Death

Schwinger died of
pancreatic cancer Pancreatic cancer arises when cell (biology), cells in the pancreas, a glandular organ behind the stomach, begin to multiply out of control and form a Neoplasm, mass. These cancerous cells have the malignant, ability to invade other parts of ...
. He is buried at
Mount Auburn Cemetery Mount Auburn Cemetery, located in Cambridge and Watertown, Massachusetts, is the first rural or garden cemetery in the United States. It is the burial site of many prominent Boston Brahmins, and is a National Historic Landmark. Dedicated in ...
; \frac, where \alpha is the fine structure constant, is engraved above his name on his tombstone. These symbols refer to his calculation of the correction ("anomalous") to the magnetic moment of the electron.


See also

* List of things named after Julian Schwinger * List of Jewish Nobel laureates * List of textbooks in electromagnetism


Selected publications

Books * Milton KA, ''A Quantum Legacy: Seminal Papers of Julian Schwinger'', World Scientific, 2000. * Milton KA, Schwinger J, ''Classical Electrodynamics'', 2nd ed, Taylor & Francis, 2024. * Milton KA, Schwinger J, ''Electromagnetic Radiation: Variational Methods, Waveguides and Accelerators'', Springer, 2006. * Schwinger J, ''Einstein's Legacy: The Unity of Space and Time'', Dover, 2002. * Schwinger J, ''Particles, Sources, and Fields'', 3 vols, CRC, 2018. * Schwinger J, ''Quantum Kinematics and Dynamics'', Westview, 2000. * Schwinger J, ''Quantum Mechanics: Symbolism of Atomic Measurements'', Springer, 2001. * Schwinger J, Saxon DS, ''Discontinuities in Waveguides'', Gordon and Breach, 1968. Articles * * * * * Feshbach, H., Schwinger, J. and J. A. Harr
"Effect of Tensor Range in Nuclear Two-Body Problems"
Computation Laboratory of
Harvard University Harvard University is a Private university, private Ivy League research university in Cambridge, Massachusetts, United States. Founded in 1636 and named for its first benefactor, the History of the Puritans in North America, Puritan clergyma ...
,
United States Department of Energy The United States Department of Energy (DOE) is an executive department of the U.S. federal government that oversees U.S. national energy policy and energy production, the research and development of nuclear power, the military's nuclear w ...
(through predecessor agency the Atomic Energy Commission) (November 1949). * * Schwinger, J
"On Angular Momentum"
Harvard University Harvard University is a Private university, private Ivy League research university in Cambridge, Massachusetts, United States. Founded in 1636 and named for its first benefactor, the History of the Puritans in North America, Puritan clergyma ...
, Nuclear Development Associates, Inc.,
United States Department of Energy The United States Department of Energy (DOE) is an executive department of the U.S. federal government that oversees U.S. national energy policy and energy production, the research and development of nuclear power, the military's nuclear w ...
(through predecessor agency the Atomic Energy Commission) (January 26, 1952). * Schwinger, J
"The Theory of Quantized Fields. II"
Harvard University Harvard University is a Private university, private Ivy League research university in Cambridge, Massachusetts, United States. Founded in 1636 and named for its first benefactor, the History of the Puritans in North America, Puritan clergyma ...
,
United States Department of Energy The United States Department of Energy (DOE) is an executive department of the U.S. federal government that oversees U.S. national energy policy and energy production, the research and development of nuclear power, the military's nuclear w ...
(through predecessor agency the Atomic Energy Commission) (1951). * Schwinger, J
"The Theory of Quantizied Fields. Part 3"
Harvard University Harvard University is a Private university, private Ivy League research university in Cambridge, Massachusetts, United States. Founded in 1636 and named for its first benefactor, the History of the Puritans in North America, Puritan clergyma ...
,
United States Department of Energy The United States Department of Energy (DOE) is an executive department of the U.S. federal government that oversees U.S. national energy policy and energy production, the research and development of nuclear power, the military's nuclear w ...
(through predecessor agency the Atomic Energy Commission) (May 1953).


References


Further reading

*Mehra, Jagdish, and Milton, Kimball A. (2000) ''Climbing the Mountain: the scientific biography of Julian Schwinger''. Oxford University Press. * Revised version published as (2007) "Julian Schwinger: From Nuclear Physics and Quantum Electrodynamics to Source Theory and Beyond," ''Physics in Perspective'' 9: 70–114. * *Ng, Y. Jack, ed. (1996) ''Julian Schwinger: The Physicist, the Teacher, and the Man''. Singapore: World Scientific. . *


External links

* including the Nobel Lecture, December 11, 1965 ''Relativistic Quantum Field Theory'' * {{DEFAULTSORT:Schwinger, Julian 1918 births 1994 deaths Nobel laureates in Physics American Nobel laureates American theoretical physicists American people of Polish-Jewish descent 20th-century American physicists Jewish American physicists National Medal of Science laureates Columbia Graduate School of Arts and Sciences alumni Columbia College (New York) alumni Harvard University faculty Purdue University faculty University of California, Los Angeles faculty Burials at Mount Auburn Cemetery Townsend Harris High School alumni Cold fusion American particle physicists Scientists from New York (state) American quantum physicists Fellows of the American Physical Society