Leonard Susskind

He recalls that his father was a plumber and that he worked with him in the South Bronx from age 13; when his father fell seriously ill at 16 he had to work a great deal during school and summers, continuing until he went to graduate school in 1962, and he was already married with a child when he studied physics.⁠[1]

He received a B.S. in physics from City College of New York in 1962 and a PhD in physics from Cornell UniversityCornell UniversityCornell University is a private research university in Ithaca, New York, and a member of the Ivy League. It is New York State's federal land-grant university, a distinction unique within the Ivy League. Ezra Cornell and Andrew Dickson White founded the university in 1865, and it opened in 1868. In addition to its Ithaca campus, Cornell operates Weill Cornell Medicine and Cornell Tech in New York City and a medical college in Qatar. It enrolled 26,793 students in fall 2024. Its president is Michael I. Kotlikoff.Open the full entry in 1965.⁠[2]

He was a National Science Foundation postdoctoral fellow in 1965–66, then taught at Yeshiva University’s Belfer Graduate School of Science as assistant professor (1966–68), associate professor (1968–70) and professor of physics (1970–79), spending 1971–72 as a professor of physics at Tel Aviv University, receiving the New York Academy of Sciences’ Pregel Award in 1975 and serving as Harvard UniversityHarvard UniversityHarvard University is a private research university in Massachusetts, established by the Massachusetts Bay Colony legislature in 1636 and named in 1639 for early benefactor John Harvard. Its principal campuses are in Cambridge and the Allston and Longwood neighborhoods of Boston. It includes Harvard College, graduate and professional schools, and the Radcliffe Institute for Advanced Study. Two governing boards share oversight. Alan M. Garber was president as of October 2026, and the endowment stood at $56.9 billion at the end of fiscal 2025.Open the full entry’s Loeb Lecturer in 1976.⁠[3]

Independently of Yoichiro Nambu and Holger Bech Nielsen, he introduced the idea that particles could be states of excitation of a relativistic string, and he is widely regarded as one of the fathers of string theory.⁠[4]

He has taught at Stanford University since 1979; colleagues describe his hallmark as bringing brilliant imagination and originality to the study of elementary particles and forces.⁠[5]

In 1981, at a conference also attended by Hawking, he learned of Hawking’s claim that black holes permanently destroy information and soon raised an objection with Thomas Banks and Michael Peskin; Hawking held his position for 28 years until publicly agreeing in 2004 that information is preserved.⁠[6]

In June 1993 he, Lárus Thorlacius and John Uglum posted “The Stretched Horizon and Black Hole Complementarity” on arXiv, building on three postulates — conventional quantum theory, semi-classical general relativity and the statistical basis of thermodynamics — and describing black hole evolution for a distant observer via a stretched horizon.⁠[7]

In September 1994 he published “The World as a Hologram,” developing Gerard ’t Hooft’s proposal that combining quantum mechanics and gravity requires the three-dimensional world to be describable by data stored on a two-dimensional projection, like a hologram.⁠[8]

In October 1996 he, Tom Banks, Willy Fischler and Stephen Shenker conjectured that uncompactified eleven-dimensional M-theory is equivalent to the large-N limit of the supersymmetric matrix quantum mechanics describing D0-branes.⁠[9]

The American Physical Society awarded him the 1998 J. J. Sakurai Prize for pioneering contributions to hadronic string models, lattice gauge theories, quantum chromodynamics and dynamical symmetry breaking.⁠[10]

In February 2003, in the lecture paper “The Anthropic Landscape of String Theory,” he conjectured that the landscape of string theory vacua is unimaginably large and diverse and argued that this lends credence to the anthropic principle.⁠[11]

In 2005 he published The Cosmic Landscape: String Theory and the Illusion of Intelligent Design, arguing that the universe’s apparent design for humans can be explained by string theory’s vast number of solutions together with a “megaverse” of continually created bubble universes; the reviewer disputed his estimate of about 10^500 solutions.⁠[12]

In 2008 Little, BrownBrown UniversityBrown University is a private nonprofit research university in Providence, Rhode Island, and a member of the Ivy League. Chartered by Rhode Island's colonial legislature in 1764, it is known for its undergraduate Open Curriculum, which has no common required core. Christina H. Paxson, president since July 2012, announced on August 3, 2026, that the 2026–27 academic year would be her last in office. As of October 1, 2026, the search for Brown's 20th president remained underway.Open the full entry published his 470-page The Black Hole War: My Battle with Stephen Hawking to Make the World Safe for Quantum Mechanics, a personal account of the debate.⁠[6]

He says Hawking was his friend and that theirs was “a ‘war’ of ideas, not a war of people.”⁠[1]

From 2009 he served as director of the Stanford Institute for Theoretical Physics, and The Black Hole War won the Los Angeles Times Book Award in Science and Technology; in May 2011 TED posted his talk “My friend Richard FeynmanRichard FeynmanRichard Feynman (Richard Phillips Feynman, 1918–1988) was an American theoretical physicist who rebuilt quantum electrodynamics with the path-integral formulation and Feynman diagrams, for which he shared the 1965 Nobel Prize in Physics with Julian Schwinger and Sin-Itiro Tomonaga. He took part in the Manhattan Project during World War II and then taught for decades at the California Institute of Technology, where his introductory physics course became The Feynman Lectures on Physics; in 1986, as a member of the presidential commission investigating the space shuttle Challenger accident, he used ice water to demonstrate that the O-ring lost its resilience at low temperature.Open the full entry,” about his friendship with Feynman.⁠[13]

In June 2013 he and Juan Maldacena published “Cool horizons for entangled black holes,” arguing that two black holes joined by a wormhole, or Einstein-Rosen bridge, can be read as a maximally entangled state and suggesting that similar bridges may exist for more general entangled states, as a response to the black hole firewall paradoxes.⁠[14]

He teaches The Theoretical Minimum, a series of modern-physics courses in Stanford’s Continuing Studies program, and writes companion books of the same name; the first volume, with George Hrabovsky, covers classical mechanics.⁠[15]

On February 25, 2014, Basic Books published the series’ second volume, Quantum Mechanics: The Theoretical Minimum, written with Art Friedman.⁠[16]

Around 2018 he and collaborators proposed that black hole interiors keep growing because the computational complexity of their quantum states keeps increasing, showing in holographic toy models that the two grow at the same rate; Stanford theorist Aron Wall called the idea exciting but still rather speculative and possibly incorrect.⁠[17]

He appeared as the guest of episode 41 of the Lex FridmanLex FridmanLex Fridman is a Soviet-born, US-raised computer scientist and podcast host who works as an MIT research scientist on human-AI interaction and autonomous driving. His Lex Fridman Podcast is known for hours-long conversations with guests including heads of state and technology leaders.Open the full entry Podcast, discussing Richard Feynman, intuition and ego in science, quantum computers, the universe as an information-processing system, string theory, free will, the arrow of time, the Big Bang and the first image of a black hole.⁠[18]

On January 10, 2023, the 400-page General Relativity: The Theoretical Minimum, written with André Cabannes, was published, moving from the equivalence principle and Riemannian geometry to black holes, Einstein’s field equations and gravitational waves.⁠[19]

The International Centre for Theoretical Physics (ICTP) gave its 2023 Dirac Medal to four string theorists including him, noting that he was among the first to see that dual models could be interpreted as strings and pointing to his work on Hamiltonian lattice gauge theory with Kogut, baryogenesis and technicolor with Dimopoulos, holography, and links between complexity and black holes.⁠[20]

In February 2025 Italy’s National Institute for Nuclear Physics and its Galileo Galilei Institute for Theoretical Physics announced that he had won the 2025 Galileo Galilei Medal for uncovering the challenges black holes pose to the classical and quantum nature of gravity and connecting elementary particles with the cosmos.⁠[21]

Wonderfest gave him its 2025 Carl Sagan Prize for Science Popularization; he explained that he had noticed many physics enthusiasts who had no teacher to ask and found popular books not deep enough, which led him to teach modern physics in depth.⁠[22]

Yeshiva University: Official website: https://www.yu.edu/ (opens in a new window)⁠[3]

Stanford University: Official website: https://www.stanford.edu/ (opens in a new window)⁠[2]