Kip Thorne

A Utah boy and a black hole

Kip Stephen Thorne was born in Logan, Utah, on June 1, 1940, into a family of academics. His father, D. Wynne Thorne, was a soil chemist at Utah State University; his mother, Alison Comish Thorne, was one of the first women in the country to earn a PhD in economics. The Thornes were Mormon, scholarly, and unfussy, and the household ran on the assumption that a child who asked a question was owed a serious answer. By eight, Kip had built a model of the solar system and decided he wanted to understand how the planets really moved. By thirteen, he had read George Gamow’s One Two Three… Infinity and was hooked on the geometry of spacetime.

He went to Caltech for his undergraduate degree in 1958 and then to Princeton for graduate work in 1962. His advisor was John Archibald Wheeler, the physicist who had coined the term “black hole” and who treated general relativity not as a curiosity but as a living theory with unfinished business. Wheeler taught his students to take Einstein’s equations at face value: if the math said a star could collapse to a point, then somewhere in the universe a star was doing exactly that, and the job of the theorist was to figure out what it looked like from the outside. Thorne finished his PhD in 1965 with a thesis on the relativistic mechanics of cylindrical bodies, and after a brief postdoc in Moscow with the Soviet relativist Yakov Zel’dovich he returned to Caltech as a junior faculty member in 1967. He never left. In 1991 Caltech named him the Richard P. Feynman Professor of Theoretical Physics, the chair held by Feynman until his death.

Gravitation, and a culture for relativity

Through the late 1960s and the 1970s Thorne built a school of relativistic astrophysics at Caltech almost from nothing. He worked on neutron stars, pulsars, accretion disks, and the conditions under which a star can collapse to a black hole. With his Princeton mentor Wheeler and the relativist Charles Misner, he co-authored Gravitation, published in 1973, a 1200-page textbook universally known as MTW. The book did for general relativity what Feynman’s Lectures had done for undergraduate physics: it took a subject that had been the preserve of a few specialists and made it teachable, lively, and central. Two generations of relativists learned the theory from MTW. Stephen Hawking once admitted he kept a copy on his desk.

Kip Stephen Thorne (born June 1, 1940) is an American astrophysicist and author. He shared the 2017 Nobel Prize in Physics with Rainer Weiss and Barry C. Barish "for decisive contributions to the LIGO detector and the observation of gravitational waves".

LIGO: thirty years of patience

In the early 1980s Thorne, the experimentalist Rainer Weiss at MIT, and the Scottish-born Caltech physicist Ronald Drever began arguing that a kilometre-scale laser interferometer could, in principle, detect the ripples in spacetime that Einstein had predicted in 1916. The signal they were after was unimaginably small: a passing gravitational wave from two colliding black holes would stretch a four-kilometre arm by less than the width of a proton. Most physicists thought the project was impossible, naive, or both. Thorne spent the next three decades arguing otherwise. He wrote the theoretical case, mentored the graduate students who built the simulations, lobbied the National Science Foundation, negotiated the inevitable scientific civil wars (Drever was eventually pushed off the project), and refused to let the enterprise die during the long years when it produced nothing but null results. LIGO was, when it was finally funded at full scale in the 1990s, the most expensive experiment in the history of the NSF.

On September 14, 2015, four days into the first observing run of the upgraded Advanced LIGO detectors, a chirp arrived from a pair of black holes that had merged 1.3 billion light-years away. The waveform matched, to within the noise, the numerical-relativity simulations that Thorne’s students and their collaborators had spent decades preparing. The signal was named GW150914. It was the first direct detection of gravitational waves and the first direct observation of a binary black hole. The 2017 Nobel Prize in Physics went to Thorne, Weiss, and Barry Barish, the Caltech experimentalist who had taken over LIGO’s management in the 1990s and dragged it across the engineering finish line. Drever had died in March of that year and could not share the prize.

Interstellar, and a working scientist’s afterlife

Thorne formally retired from his Caltech chair in 2009 to spend more time on, of all things, a movie. With the producer Lynda Obst he had been developing a science-fiction film built around real general relativity, and in 2014 Interstellar arrived in theatres with Thorne as executive producer and science advisor. The black hole at the centre of the film, Gargantua, was ray-traced from the geodesic equations Thorne supplied to the visual-effects team; the image was so accurate that the production yielded two refereed papers on gravitational lensing. His companion book The Science of Interstellar, written that same year, walks the public through what in the film was plausible, what was speculative, and what was outright artistic licence. He has written for the public ever since, on time travel, on wormholes, on the lessons of LIGO, with the steady patience of a man who has spent his life waiting for a signal.

What he means to the quantum story

Thorne is the bridge. Quantum mechanics gave the twentieth century its small-scale machinery; Einstein’s general relativity gave it its large-scale geometry; gravitational waves are where the two will eventually be forced to meet. By proving that Einstein’s century-old ripple in spacetime is a measurable, repeatable, instrument-grade signal, Thorne and his collaborators handed the next century the data stream from which a quantum theory of gravity will, sooner or later, have to be read off.