Kip Thorne

• 1. Introduction

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  Kip Thorne is an American astrophysicist whose life's work converged on a single announcement. On the 11th of February 2016, four physicists speaking for the LIGO Scientific Collaboration said that their instrument had recorded two black holes colliding 1.3 billion light-years away. The signal had arrived in September 2015. It was the first direct observation of a gravitational wave, a fleeting chirp that confirmed a prediction of the general theory of relativity.

  In 2017, Thorne shared the Nobel Prize in Physics with Rainer Weiss and Barry C. Barish. The citation honored decisive contributions to the LIGO detector and the observation of gravitational waves.

  But the detector is only one thread. How did a professor's son from Logan, Utah, end up shaping the theory of black holes? What does it mean to ask whether a wormhole could be a time machine? And how did a theoretical physicist come to advise some of the most ambitious films of his era?

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• 2. Utah Roots

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  Logan, Utah, is where Thorne was born, on the 1st of June 1940. His father, D. Wynne Thorne, was a professor of soil chemistry at Utah State University. His mother, Alison, was an economist, and she was the first woman to earn a PhD in economics from Iowa State College. Two of his four siblings also became professors.

  The Church of Jesus Christ of Latter-day Saints shaped the household, and both parents raised the children in it. Shortly before she died, Alison urged Kip and his siblings to leave the church because of its discrimination against women. All of them did. Thorne now identifies as an atheist, yet he does not see science and religion as enemies. In his words: "There are large numbers of my finest colleagues who are quite devout and believe in God.... There is no fundamental incompatibility between science and religion. I happen to not believe in God."

  At Logan High School, he earned recognition in the Westinghouse Science Talent Search as a senior. He took a physics degree at Caltech in 1962. Princeton followed, with a master's degree in 1964 and a doctorate in 1965. His adviser was John Archibald Wheeler, and his dissertation was titled Geometrodynamics of Cylindrical Systems.

  Caltech brought him back in 1967 as an associate professor. By 1970 he held a full professorship in theoretical physics at the age of 30, among the youngest in the school's history. He became the William R. Kenan, Jr. Professor in 1981 and the Feynman Professor of Theoretical Physics in 1991. From 1971 to 1998 he also served as an adjunct professor at the University of Utah. Cornell named him Andrew D. White Professor at Large from 1986 to 1992. In June 2009 he resigned the Feynman chair to pursue writing and moviemaking, and he now holds it as professor emeritus.

  The cylinder in his dissertation title was no accident, because Wheeler had handed him a puzzle about cylinders that would grow into his first major idea.

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• 3. Black Holes and Stars

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  Wheeler's puzzle concerned a cylindrical bundle of repulsive magnetic field lines. Would it collapse under its own gravity? After several months of struggle, Thorne proved that it could not.

  That answer created a paradox of its own, since spherical stars certainly do collapse. Thorne went looking for the boundary between the two cases. He concluded that gravity overwhelms every internal pressure only when an object has been squeezed in all directions at once. His proposal became the hoop conjecture. Imagine a hoop with a circumference of four pi times Newton's gravitational constant times the mass, divided by the speed of light squared. If such a hoop can be spun around an object of mass M, that object must be a black hole.

  Thorne and his students later built an unusual approach called the membrane paradigm for thinking about black holes. They used it to clarify the Blandford-Znajek mechanism, by which black holes may power some quasars and active galactic nuclei.

  Entropy was another target. With his postdoc Wojciech Zurek, Thorne showed that a black hole's entropy is the logarithm of the number of ways the hole could have been made. Together with Igor Novikov and Don Page, he worked out the relativistic theory of thin accretion disks around black holes. From that theory he deduced a ceiling on spin. A hole that doubles its mass by accretion spins up to 0.998 of the maximum general relativity allows, and no higher. This is probably the limit in nature.

  Stars drew his attention too. With Anna Żytkow, he predicted red supergiant stars with neutron-star cores, now called Thorne-Żytkow objects. He laid the foundations for the theory of pulsations in relativistic stars and the gravitational radiation they emit. With James Hartle, he derived the laws of motion and precession for black holes and other relativistic bodies. Their work also produced the Hartle-Thorne metric, an approximate description of the space outside a slowly and rigidly rotating body.

  Clifford Will and other students of Thorne laid foundations for interpreting experimental tests of gravity theories, and Will and others built on them. As of 2005, Thorne was asking how classical space and time arise from the quantum foam of quantum gravity.

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• 4. Wormholes and Paradoxes

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  Mike Morris and Ulvi Yurtsever joined Thorne for a result that startled fellow physicists. They showed that a traversable wormhole can exist in spacetime only if it is threaded by quantum fields in states that violate the averaged null energy condition. Such states have negative renormalized energy spread over a sufficiently large region. That finding set off a search for whether quantum fields can hold negative energy over such extended regions.

  Sung-Won Kim worked with Thorne on the opposite question. They identified a universal mechanism, the explosive growth of vacuum polarization in quantum fields. It may always prevent spacetime from forming closed timelike curves, which would rule out travel into the past.

  Thorne also predicted the existence of universally antigravitating exotic matter. This is the ingredient needed to speed up the expansion of the universe. It would also hold traversable wormhole Star Gates open and keep free-floating warp drives working.

  Then came the paradoxes. Recent calculations by Thorne indicate that simple masses passing through traversable wormholes could never produce a paradox. No starting conditions lead to one once time travel is allowed. If the results generalize, none of the paradoxes in time travel fiction could even be stated at a precise physical level. Each situation in such a story would permit many consistent solutions.

  A paper with the title Cauchy Problem in Spacetimes with Closed Timelike Curves, listed as in press at Physical Review D in 1990, carries his name beside Friedman, Morris, Novikov, Echeverria, Klinkhammer and Yurtsever.

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• 5. Building LIGO

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  In 1984, Thorne cofounded the LIGO Project, which became the largest project the National Science Foundation had ever funded. The name stands for Laser Interferometer Gravitational Wave Observatory. It is a multi-institution experiment designed to detect fluctuations between two or more static points. According to calculations, such fluctuations would be evidence of gravitational waves.

  Thorne's role spanned theory and engineering. He predicted the strengths of gravitational waves and their time signatures as observed on Earth. Developing the mathematics to analyze these signals was a significant part of the task. He carried out engineering design analyses for features of the detector that experiments could not settle. He also gave advice on the data analysis algorithms used in the hunt for the waves.

  He helped identify the sources that LIGO should target. He also designed the baffles that control scattered light in the beam tubes.

  The research group of Vladimir Braginsky in Moscow became a key partner. Together they invented quantum nondemolition designs for advanced gravity-wave detectors. They also found ways to reduce thermoelastic noise, the most serious kind of noise in advanced detectors.

  With Carlton M. Caves, Thorne invented the back-action-evasion approach to quantum nondemolition measurements of harmonic oscillators. The technique applies to gravitational wave detection and also to quantum optics.

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• 6. Teaching and Books

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  Approximately 50 physicists have earned PhDs at Caltech under Thorne's personal mentorship. Many of them are now leading theorists who work on observational, experimental or astrophysical aspects of general relativity.

  In 1973, Gravitation appeared, coauthored with Charles Misner and John A. Wheeler. John C. Baez and Chris Hillman have called it one of the great scientific books of all time. They say it inspired two generations of students.

  Black Holes and Time Warps arrived in 1994, a popular book that follows black holes from John Michell to Stephen Hawking and beyond. It has been published in fourteen languages. German came the same year, then Spanish in 1995, and French and Japanese in 1997. Greek followed in 1999, and Czech in 2004. Polish, Chinese and Korean editions arrived in 2005, Thai in 2008 and Italian in 2013.

  Christopher Nolan wrote the foreword to The Science of Interstellar, which Thorne published in 2014 to explain the physics behind the film. In September 2017, Thorne and Roger D. Blandford released Modern Classical Physics, a graduate textbook covering optics, fluids, plasmas, elasticity, relativity and statistical physics. With the artist Lia Halloran, he explored astrophysics through poetry and illustration in The Warped Side of Our Universe. His shorter writing has appeared in Scientific American, and he has published more than 150 articles in scholarly journals.

  PBS shows in the United States and programs on the BBC in the United Kingdom have featured his talks on black holes, gravitational radiation, relativity, time travel and wormholes. In 2017, he delivered the George Gamow Memorial Lecture at the University of Colorado Boulder. Its title was "Probing the Warped Side of the Universe with Gravitational Waves: From the Big Bang to Black Holes."

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• 7. Stories and Screens

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  Linda Jean Peterson and Thorne married in 1960. They had two children, Kares Anne and Bret Carter, who became an architect. The couple divorced in 1977.

  Two years later, Carl Sagan set Thorne up on a blind date with Lynda Obst, who later became a film producer. They dated in 1979-1980 and then parted as friends. In 1984, Thorne married Carolee Joyce Winstein, a professor of biokinesiology and physical therapy at USC.

  Sagan, a longtime friend, turned to Thorne for the physics of wormholes in his novel Contact. Years later, Thorne and Obst developed the concept for Christopher Nolan's film Interstellar. Thorne served as a scientific consultant on that film and on Nolan's Tenet. He also advised Cillian Murphy on playing J. Robert Oppenheimer in Nolan's Oppenheimer. In 2015, Thorne, Obst and Stephen Hawking wrote several drafts of a movie script together.

  Thorne has also turned up on screen as a character. The actor Enzo Cilenti played him in the film The Theory of Everything. Thorne played himself in the Big Bang Theory episode titled "The Laureate Accumulation." He appears too in an episode of the documentary series The Craftsman called "Science, Art & Inspiration."

  In Larry Niven's novel Rainbow Mars, time travel rests on Thorne's wormhole theories. Any traveler who tries to go back before those theories existed ends up in a fantastic version of reality instead of the real past.

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• 8. Honors

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  Time magazine placed Thorne on its list of the 100 most influential people in 2016, a year that also brought a wave of prizes. He received the Special Breakthrough Prize in Fundamental Physics and the Gruber Prize in Cosmology. He shared the Shaw Prize and the Kavli Prize in Astrophysics with Ronald Drever and Rainer Weiss. The Harvey Prize came with the same two co-recipients. Further 2016 honors included the Tomalla Prize, the Georges Lemaître Prize and the Smithsonian Magazine American Ingenuity Award for Physical Sciences.

  The European Physical Society gave him its Cocconi Prize jointly with Weiss and Barish. In 2017, the three men also shared the Princess of Asturias Award.

  The German Astronomical Society awarded him its Karl Schwarzschild Medal in 1996. The California Science Center named him California Scientist of the Year in 2003. In 2009, the Albert Einstein Society in Bern gave him the Albert Einstein Medal, and that year he also held the Lorentz chair at Leiden University. UNESCO presented him with its Niels Bohr Medal in 2010. He was elected to the American Academy of Arts and Sciences in 1972, and later to the National Academy of Sciences, the Russian Academy of Sciences and the American Philosophical Society.

  His writing earned the American Institute of Physics Science Writing Award and the Phi Beta Kappa Science Writing Award. In 2018 he received the Lewis Thomas Prize, and in 2019 the Golden Plate Award of the American Academy of Achievement. He has been a Woodrow Wilson Fellow, a Danforth Fellow, a Guggenheim Fellow and a Fulbright Fellow. He has also served on the International Committee on General Relativity and Gravitation and the Committee on US-USSR Cooperation in Physics. His seat on the National Academy of Sciences' Space Science Board put him in the role of advising NASA and Congress.

  Honorary degrees have come from Claremont Graduate University, Aristotle University of Thessaloniki and, in 2024, the University of Cambridge. The most recent, in 2026, was an honorary Doctor of Science from Rochester Institute of Technology.

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