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62-602: Steven Weinberg ( / ˈ w aɪ n b ɜːr ɡ / ; 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 interaction between elementary particles. He held the Josey Regental Chair in Science at the University of Texas at Austin , where he

124-549: A luminiferous aether . Conversely, Einstein was awarded the Nobel Prize for explaining the photoelectric effect , previously an experimental result lacking a theoretical formulation. A physical theory is a model of physical events. It is judged by the extent to which its predictions agree with empirical observations. The quality of a physical theory is also judged on its ability to make new predictions which can be verified by new observations. A physical theory differs from

186-504: A mathematical theorem in that while both are based on some form of axioms , judgment of mathematical applicability is not based on agreement with any experimental results. A physical theory similarly differs from a mathematical theory , in the sense that the word "theory" has a different meaning in mathematical terms. R i c = k g {\displaystyle \mathrm {Ric} =kg} The equations for an Einstein manifold , used in general relativity to describe

248-439: A postdoctoral researcher at Columbia University (1957–59) and University of California, Berkeley (1959) and then was promoted to faculty at Berkeley (1960–66). He did research in a variety of topics of particle physics, such as the high energy behavior of quantum field theory , symmetry breaking , pion scattering, infrared photons and quantum gravity ( soft graviton theorem ). It was also during this time that he developed

310-707: A solar observatory was part of the inspiration behind the Smithsonian's "sunburst" logo , designed in 1965 by Crimilda Pontes . In 1955, the scientific headquarters of SAO moved from Washington, D.C. to Cambridge, Massachusetts to affiliate with the Harvard College Observatory (HCO). Fred Lawrence Whipple , then the chairman of the Harvard Astronomy Department, was named the new director of SAO. The collaborative relationship between SAO and HCO therefore predates

372-475: A working hypothesis . Smithsonian Astrophysical Observatory The Smithsonian Astrophysical Observatory ( SAO ) is a research institute of the Smithsonian Institution , concentrating on astrophysical studies including galactic and extragalactic astronomy , cosmology , solar , earth and planetary sciences , theory and instrumentation, using observations at wavelengths from

434-404: A certain economy and elegance (compare to mathematical beauty ), a notion sometimes called " Occam's razor " after the 13th-century English philosopher William of Occam (or Ockham), in which the simpler of two theories that describe the same matter just as adequately is preferred (but conceptual simplicity may mean mathematical complexity). They are also more likely to be accepted if they connect

496-500: A form of protoscience and others are a form of pseudoscience . The falsification of the original theory sometimes leads to reformulation of the theory. "Thought" experiments are situations created in one's mind, asking a question akin to "suppose you are in this situation, assuming such is true, what would follow?". They are usually created to investigate phenomena that are not readily experienced in every-day situations. Famous examples of such thought experiments are Schrödinger's cat ,

558-636: A hospital in Austin , where he had been undergoing treatment for several weeks. Weinberg's papers were donated to the Harry Ransom Center at the University of Texas. Weinberg identified as a liberal. Weinberg was an atheist. Before he was an advocate of the Big Bang theory , Weinberg said: "The steady-state theory is philosophically the most attractive theory because it least resembles

620-498: A new branch of mathematics: infinite, orthogonal series . Modern theoretical physics attempts to unify theories and explain phenomena in further attempts to understand the Universe , from the cosmological to the elementary particle scale. Where experimentation cannot be done, theoretical physics still tries to advance through the use of mathematical models. Mainstream theories (sometimes referred to as central theories ) are

682-492: A new law allowing the carrying of concealed guns in UT classrooms. He announced that he would prohibit guns in his classes, and said he would stand by his decision to violate university regulations in this matter even if faced with a lawsuit. Weinberg never retired and taught at UT until his death. In 1954 Weinberg married legal scholar Louise Goldwasser and they had a daughter, Elizabeth. Weinberg died on July 23, 2021, at age 88 at

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744-534: A particularly eloquent spokesperson for the scientific worldview". Brian Greene said that Weinberg had an “astounding ability to see into the deep workings of nature” that “profoundly shaped our understanding of the universe". Upon the awarding of the Breakthrough Prize in 2020, one of the founders of the prizes, Yuri Milner , called Weinberg a “key architect” of “one of the most successful physical theories ever”, while string theorist Juan Maldacena ,

806-465: A physical system might be modeled; e.g., the notion, due to Riemann and others, that space itself might be curved. Theoretical problems that need computational investigation are often the concern of computational physics . Theoretical advances may consist in setting aside old, incorrect paradigms (e.g., aether theory of light propagation, caloric theory of heat, burning consisting of evolving phlogiston , or astronomical bodies revolving around

868-469: A wide range of phenomena. Testing the consequences of a theory is part of the scientific method . Physical theories can be grouped into three categories: mainstream theories , proposed theories and fringe theories . Theoretical physics began at least 2,300 years ago, under the Pre-socratic philosophy , and continued by Plato and Aristotle , whose views held sway for a millennium. During

930-410: Is often regarded as the leading book in the field. In 1966, Weinberg left Berkeley and accepted a lecturer position at Harvard. In 1967 he was a visiting professor at MIT. It was in that year at MIT that Weinberg proposed his model of unification of electromagnetism and nuclear weak forces (such as those involved in beta-decay and kaon -decay), with the masses of the force-carriers of the weak part of

992-620: The Center for Astrophysics | Harvard & Smithsonian (CfA) under a single Director. Samuel Pierpont Langley , the third Secretary of the Smithsonian , founded the Smithsonian Astrophysical Observatory on the south yard of the Smithsonian Castle (on the U.S. National Mall ) on March 1, 1890 . The Astrophysical Observatory's initial, primary purpose was to " record the amount and character of

1054-539: The EPR thought experiment , simple illustrations of time dilation , and so on. These usually lead to real experiments designed to verify that the conclusion (and therefore the assumptions) of the thought experiments are correct. The EPR thought experiment led to the Bell inequalities , which were then tested to various degrees of rigor , leading to the acceptance of the current formulation of quantum mechanics and probabilism as

1116-572: The Scientific Revolution gathered pace, the concepts of matter , energy, space, time and causality slowly began to acquire the form we know today, and other sciences spun off from the rubric of natural philosophy . Thus began the modern era of theory with the Copernican paradigm shift in astronomy, soon followed by Johannes Kepler 's expressions for planetary orbits, which summarized the meticulous observations of Tycho Brahe ;

1178-604: The Telluride House . He then went to the Niels Bohr Institute in Copenhagen, where he started his graduate studies and research. After one year, Weinberg moved to Princeton University , where he earned his Ph.D. in physics in 1957, completing his dissertation, "The role of strong interactions in decay processes", under the supervision of Sam Treiman . After completing his Ph.D., Weinberg worked as

1240-522: The University of Texas at Austin as the Jack S. Josey-Welch Foundation Regents Chair in Science, and started a theoretical physics group at the university that now has eight full professors and is one of the leading research groups in the field in the U.S. Weinberg is frequently listed among the top scientists with the highest research effect indices, such as the h-index and the creativity index. The theoretical physicist Peter Woit called Weinberg "arguably

1302-506: The Z boson . The 1973 experimental discovery of weak neutral currents (mediated by this Z boson) was one verification of the electroweak unification. The paper by Weinberg in which he presented this theory is one of the most cited works ever in high-energy physics. After his 1967 seminal work on the unification of weak and electromagnetic interactions, Weinberg continued his work in many aspects of particle physics, quantum field theory, gravity, supersymmetry , superstrings and cosmology . In

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1364-603: The quantum mechanical idea that ( action and) energy are not continuously variable. Theoretical physics consists of several different approaches. In this regard, theoretical particle physics forms a good example. For instance: " phenomenologists " might employ ( semi- ) empirical formulas and heuristics to agree with experimental results, often without deep physical understanding . "Modelers" (also called "model-builders") often appear much like phenomenologists, but try to model speculative theories that have certain desirable features (rather than on experimental data), or apply

1426-461: The two-fluid theory of electricity are two cases in this point. However, an exception to all the above is the wave–particle duality , a theory combining aspects of different, opposing models via the Bohr complementarity principle . Physical theories become accepted if they are able to make correct predictions and no (or few) incorrect ones. The theory should have, at least as a secondary objective,

1488-413: The 1970s, he proposed a theory later known as technicolor , in which new strong interactions resolve the hierarchy problem . Weinberg became Eugene Higgins Professor of Physics at Harvard University in 1973, a post he held until 1983. In 1979 he pioneered the modern view on the renormalization aspect of quantum field theory that considers all quantum field theories effective field theories and changed

1550-429: The 19th century. Another important event in the 19th century was the discovery of electromagnetic theory , unifying the previously separate phenomena of electricity, magnetism and light. The pillars of modern physics , and perhaps the most revolutionary theories in the history of physics, have been relativity theory and quantum mechanics . Newtonian mechanics was subsumed under special relativity and Newton's gravity

1612-476: The Dutchmen Snell and Huygens. In the 18th and 19th centuries Joseph-Louis Lagrange , Leonhard Euler and William Rowan Hamilton would extend the theory of classical mechanics considerably. They picked up the interactive intertwining of mathematics and physics begun two millennia earlier by Pythagoras. Among the great conceptual achievements of the 19th and 20th centuries were the consolidation of

1674-587: The Earth ) or may be an alternative model that provides answers that are more accurate or that can be more widely applied. In the latter case, a correspondence principle will be required to recover the previously known result . Sometimes though, advances may proceed along different paths. For example, an essentially correct theory may need some conceptual or factual revisions; atomic theory , first postulated millennia ago (by several thinkers in Greece and India ) and

1736-754: The Philosophical Society of Texas, and member of the Board of Editors of Daedalus magazine, the Council of Scholars of the Library of Congress , the JASON group of defense consultants, and many other boards and committees. Steven Weinberg was born in 1933 in New York City. His parents were Jewish immigrants; his father, Frederick, worked as a court stenographer, while his mother, Eva (Israel),

1798-698: The SAO, including affiliated research staff. In addition, the SAO has about 120 postdoctoral researchers/fellows working in five competitive, associated fellowship programs: CfA, Clay, SMA, ITAMP, and Leon Van Speybroeck , or in support of a contract or grant. (Additional postdocs do research via Harvard fellowship programs or national/international fellowship awards); about 40% of the postdoctoral community are women and about 12% are from minority populations. SAO scientists can supervise Harvard Ph.D students, and in addition they typically supervise about 30 graduate students from other institutions who are pursuing Ph.D. theses at

1860-584: The Sun's heat ". Charles Greeley Abbot was named SAO's first director, and the observatory operated solar telescopes to take daily measurements of the Sun 's intensity in different regions of the optical electromagnetic spectrum . In doing so, the observatory enabled Abbot to make critical refinements to the Solar constant , as well as to serendipitously discover Solar variability . It is likely that SAO's early history as

1922-591: The account given in Genesis." Weinberg was known for his support of Israel , which he characterized as "the 'most exposed salient' in a war between liberal democracies and Muslim theocracies." He wrote the 1997 essay "Zionism and Its Adversaries" on the issue. In the 2000s, Weinberg canceled trips to universities in the United Kingdom because of the British boycotts of Israel . At the time, he said: "Given

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1984-419: The applications of relativity to problems in astronomy and cosmology respectively . All of these achievements depended on the theoretical physics as a moving force both to suggest experiments and to consolidate results — often by ingenious application of existing mathematics, or, as in the case of Descartes and Newton (with Leibniz ), by inventing new mathematics. Fourier's studies of heat conduction led to

2046-554: The approach to quantum field theory described in the first chapters of his book The Quantum Theory of Fields and started to write his textbook Gravitation and Cosmology , having taken up an interest in general relativity after the discovery of cosmic microwave background radiation . He was also appointed the senior scientist at the Smithsonian Astrophysical Observatory . The Quantum Theory of Fields spanned three volumes and over 1,500 pages, and

2108-514: The body of knowledge of both factual and scientific views and possess a usual scientific quality of the tests of repeatability, consistency with existing well-established science and experimentation. There do exist mainstream theories that are generally accepted theories based solely upon their effects explaining a wide variety of data, although the detection, explanation, and possible composition are subjects of debate. The proposed theories of physics are usually relatively new theories which deal with

2170-504: The chair of the selection committee, said, “Steven Weinberg has developed many of the key theoretical tools that we use for the description of nature at a fundamental level". Besides his scientific research, Weinberg was a public spokesman for science, testifying before Congress in support of the Superconducting Super Collider , writing articles for The New York Review of Books , and giving various lectures on

2232-441: The curvature of spacetime A physical theory involves one or more relationships between various measurable quantities. Archimedes realized that a ship floats by displacing its mass of water, Pythagoras understood the relation between the length of a vibrating string and the musical tone it produces. Other examples include entropy as a measure of the uncertainty regarding the positions and motions of unseen particles and

2294-466: The dominant figure in theoretical particle physics during its period of great success from the late sixties to the early eighties", calling his contribution to electroweak unification "to this day at the center of the Standard Model, our best understanding of fundamental physics". Science News named him along with fellow theorists Murray Gell-Mann and Richard Feynman the leading physicists of

2356-445: The era, commenting, "Among his peers, Weinberg was one of the most respected figures in all of physics or perhaps all of science". Sean Carroll called Weinberg one of the “best physicists we had; one of the best thinkers of any variety” who “exhibited extraordinary verve and clarity of thought through the whole stretch of a long and productive life”, while John Preskill called him "one of the most accomplished scientists of our age, and

2418-465: The following year and throughout the space race , SAO led major efforts in the development of orbiting observatories and large ground-based telescopes , laboratory and theoretical astrophysics , as well as the application of computers to astrophysical problems. SAO has operated a number of remote stations over the years. The current director of the SAO is Lisa Kewley (2022 to present). There are currently about 170 research staff working at

2480-548: The highest energy gamma rays to the radio , along with gravitational waves .  Established in Washington, D.C. , in 1890, the SAO moved its headquarters in 1955 to Cambridge, Massachusetts , where its research is a collaboration with the Harvard College Observatory (HCO) and the Harvard University Department of Astronomy. In 1973, the Smithsonian and Harvard formalized the collaboration as

2542-416: The highest order, writing Principia Mathematica . In it contained a grand synthesis of the work of Copernicus, Galileo and Kepler; as well as Newton's theories of mechanics and gravitation, which held sway as worldviews until the early 20th century. Simultaneously, progress was also made in optics (in particular colour theory and the ancient science of geometrical optics ), courtesy of Newton, Descartes and

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2604-723: The history of science, efforts that culminated in To Explain the World: The Discovery of Modern Science (2015). A hostile review in the Wall Street Journal by Steven Shapin attracted a number of commentaries, a response by Weinberg, and an exchange of views between Weinberg and Arthur Silverstein in the NYRB in February 2016. In 2016, Weinberg became a default leader for faculty and students opposed to

2666-464: The history of the attacks on Israel and the oppressiveness and aggressiveness of other countries in the Middle East and elsewhere, boycotting Israel indicated a moral blindness for which it is hard to find any explanation other than antisemitism." A list of Weinberg's publications can be found on arXiv and Scopus . Theoretical physics The advancement of science generally depends on

2728-455: The idea of energy (as well as its global conservation) by the inclusion of heat , electricity and magnetism , and then light . The laws of thermodynamics , and most importantly the introduction of the singular concept of entropy began to provide a macroscopic explanation for the properties of matter. Statistical mechanics (followed by statistical physics and Quantum statistical mechanics ) emerged as an offshoot of thermodynamics late in

2790-465: The interaction being explained by spontaneous symmetry breaking . One of its fundamental aspects was the prediction of the existence of the Higgs boson . Weinberg's model, now known as the electroweak unification theory, had the same symmetry structure as that proposed by Glashow in 1961: both included the then-unknown weak interaction mechanism between leptons , known as neutral current and mediated by

2852-570: The interplay between experimental studies and theory . In some cases, theoretical physics adheres to standards of mathematical rigour while giving little weight to experiments and observations. For example, while developing special relativity , Albert Einstein was concerned with the Lorentz transformation which left Maxwell's equations invariant, but was apparently uninterested in the Michelson–Morley experiment on Earth 's drift through

2914-604: The larger meaning of science. His books on science written for the public combine the typical scientific popularization with what is traditionally considered history and philosophy of science and atheism . His first popular science book, The First Three Minutes: A Modern View of the Origin of the Universe (1977), described the start of the universe with the Big Bang and enunciated a case for its expansion . Although still teaching physics, in later years he turned his hand to

2976-675: The late 1920s. In the aftermath of World War 2, more progress brought much renewed interest in QFT, which had since the early efforts, stagnated. The same period also saw fresh attacks on the problems of superconductivity and phase transitions, as well as the first applications of QFT in the area of theoretical condensed matter. The 1960s and 70s saw the formulation of the Standard model of particle physics using QFT and progress in condensed matter physics (theoretical foundations of superconductivity and critical phenomena , among others ), in parallel to

3038-503: The neutral currents—i.e. the discovery of the inferred existence of the Z boson —but after the 1978 experimental discovery of the theory's predicted amount of parity violation due to Z bosons' mixing with electromagnetic interactions, Weinberg was awarded the Nobel Prize in physics with Glashow and Salam, who had independently proposed a theory of electroweak unification based on spontaneous symmetry breaking. In 1982 Weinberg moved to

3100-536: The official creation of the CfA by 18 years. SAO's move to Harvard's campus also resulted in a rapid expansion of its research program. Following the launch of Sputnik (the world's first human-made satellite) in 1957, SAO accepted a national challenge to create a worldwide satellite-tracking network, collaborating with the United States Air Force on Project Space Track . With the creation of NASA

3162-419: The process of becoming established and some proposed theories. It can include speculative sciences. This includes physics fields and physical theories presented in accordance with known evidence, and a body of associated predictions have been made according to that theory. Some fringe theories go on to become a widely accepted part of physics. Other fringe theories end up being disproven. Some fringe theories are

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3224-607: The rise of medieval universities , the only acknowledged intellectual disciplines were the seven liberal arts of the Trivium like grammar , logic , and rhetoric and of the Quadrivium like arithmetic , geometry , music and astronomy . During the Middle Ages and Renaissance , the concept of experimental science, the counterpoint to theory, began with scholars such as Ibn al-Haytham and Francis Bacon . As

3286-484: The study of physics which include scientific approaches, means for determining the validity of models and new types of reasoning used to arrive at the theory. However, some proposed theories include theories that have been around for decades and have eluded methods of discovery and testing. Proposed theories can include fringe theories in the process of becoming established (and, sometimes, gaining wider acceptance). Proposed theories usually have not been tested. In addition to

3348-443: The techniques of mathematical modeling to physics problems. Some attempt to create approximate theories, called effective theories , because fully developed theories may be regarded as unsolvable or too complicated . Other theorists may try to unify , formalise, reinterpret or generalise extant theories, or create completely new ones altogether. Sometimes the vision provided by pure mathematical systems can provide clues to how

3410-472: The theories like those listed below, there are also different interpretations of quantum mechanics , which may or may not be considered different theories since it is debatable whether they yield different predictions for physical experiments, even in principle. For example, AdS/CFT correspondence , Chern–Simons theory , graviton , magnetic monopole , string theory , theory of everything . Fringe theories include any new area of scientific endeavor in

3472-405: The viewpoint of previous work (including his own in his 1967 paper) that a sensible quantum field theory must be renormalizable. This approach allowed the development of effective theory of quantum gravity, low energy QCD, heavy quark effective field theory and other developments, and is a topic of considerable interest in current research. In 1979, some six years after the experimental discovery of

3534-530: The works of these men (alongside Galileo's) can perhaps be considered to constitute the Scientific Revolution. The great push toward the modern concept of explanation started with Galileo , one of the few physicists who was both a consummate theoretician and a great experimentalist . The analytic geometry and mechanics of Descartes were incorporated into the calculus and mechanics of Isaac Newton , another theoretician/experimentalist of

3596-621: The world today." He was elected to the U.S. National Academy of Sciences , Britain's Royal Society , the American Philosophical Society, and the American Academy of Arts and Sciences . Weinberg's articles on various subjects occasionally appeared in The New York Review of Books and other periodicals. He served as a consultant at the U.S. Arms Control and Disarmament Agency , president of

3658-478: The years after 1967, the full Standard Model of elementary particle theory was developed through the work of many contributors. In it, the weak and electromagnetic interactions already unified by the work of Weinberg, Salam and Glashow, are made consistent with a theory of the strong interactions between quarks, in one overarching theory. In 1973, Weinberg proposed a modification of the Standard Model that did not contain that model's fundamental Higgs boson. Also during

3720-437: Was a housewife. Becoming interested in science at age 16 through a chemistry set handed down by a cousin, he graduated from Bronx High School of Science in 1950. He was in the same graduating class as Sheldon Glashow , whose research, independent of Weinberg's, resulted in their (and Abdus Salam 's) sharing the 1979 Nobel in physics. Weinberg received his bachelor's degree from Cornell University in 1954. There he resided at

3782-658: Was a member of the Physics and Astronomy Departments. His research on elementary particles and physical cosmology was honored with numerous prizes and awards, including the 1979 Nobel Prize in physics and the 1991 National Medal of Science . In 2004, he received the Benjamin Franklin Medal of the American Philosophical Society , with a citation that said he was "considered by many to be the preeminent theoretical physicist alive in

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3844-422: Was given a kinematic explanation by general relativity . Quantum mechanics led to an understanding of blackbody radiation (which indeed, was an original motivation for the theory) and of anomalies in the specific heats of solids — and finally to an understanding of the internal structures of atoms and molecules . Quantum mechanics soon gave way to the formulation of quantum field theory (QFT), begun in

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