Martin Rees: Stephen Hawking — An Appreciation

Soon after I enrolled as a graduate student at Cambridge University in 1964, I encountered a fellow student, two years ahead of me in his studies; he was unsteady on his feet and spoke with great difficulty. This was Stephen Hawking. He had recently been diagnosed with a degenerative disease, and it was thought that he might not survive long enough even to finish his PhD. But, amazingly, he lived on to the age of 76. Even mere survival would have been a medical marvel, but of course he didn’t just survive. He become one of the most famous scientists  in the world—acclaimed  as a world-leading researcher in mathematical physics, for his best-selling books about space, time, and the cosmos, and for his astonishing triumph over adversity.

Astronomers are used to large numbers. But few numbers could be as large as the odds I’d have given, back in 1964 when Stephen received his ‘death sentence,’ against witnessing this uniquely inspiring crescendo of achievement sustained for more than 50 years. Few, if any, of Einstein’s successors have done more to deepen our insights into gravity, space, and time.

Stephen went to school in St Albans, near London, and then to Oxford University. He was, by all accounts, a ‘laid back’ undergraduate, but his brilliance nonetheless earned him a first class degree in physics, and an ‘entry ticket’ to a research career in Cambridge. Within a few years of the onset of his disease he was wheelchair-bound, and his speech was an indistinct croak that could only be interpreted by those who knew him. But in other respects fortune had favored him. He married a family friend, Jane Wilde, who provided a supportive home life for him and their three children, Robert, Lucy, and Tim.

The 1960s were an exciting period in astronomy and cosmology: this was the decade when evidence began to emerge for black holes and the big bang. In Cambridge, Stephen  joined a lively research group. It was headed by Dennis Sciama, an enthusiastic and effective mentor who urged him to focus on the new mathematical concepts being developed by Roger Penrose, then at London University, which were initiating a renaissance in the study of Einstein’s theory of general relativity. Stephen mastered Penrose’s techniques and quickly came up with a succession of insights into the nature of black holes (then a very new idea),   along with new arguments that our universe had expanded from a ‘big bang.’ The latter work was done jointly with George Ellis, another of Sciama’s students, with whom Stephen wrote a monograph entitled The Large-Scale Structure of Space-Time. Especially important was the realization that the area of a black hole’s horizon (the ‘one-way membranes’ that shroud the interior of black holes, and from within which nothing can escape) could never decrease. The analogy with entropy (a measure of disorder, that likewise can never decrease) was developed further by the late Israeli theorist Jacob Bekenstein. In the subsequent decades, the observational support for these ideas  has strengthened—most spectacularly with the 2016 announcement of the detection of gravitational waves from colliding black holes.

Stephen was elected to the Royal Society, Britain’s main scientific academy, at the exceptionally early age of 32. He was by then so frail that most of us suspected that he could scale no further heights. But, for Stephen, this was still just the beginning. He worked in the same building as I did. I would often push his wheelchair into his office, and he would ask me to open an abstruse book on quantum theory—the science of atoms, not a subject that had hitherto much interested him. He would sit hunched motionless for hours—he couldn’t even to turn the pages without help. I wondered what was going through his mind, and if his powers were failing. But within a year he came up with his best-ever idea—encapsulated in an equation that he said he wanted on his memorial stone.

The great advances in science generally involve  discovering a link between phenomena that seemed hitherto conceptually unconnected: for instance, Isaac Newton famously realized that the force making an apple fall was the same as the force that held the moon and planets in their orbits. Stephen’s ‘eureka moment’ revealed a profound and unexpected  link between gravity and quantum theory: he predicted that black holes would not be completely black, but would radiate in a characteristic way. Bekenstein’s concept that black holes had ‘entropy’ was more than just an analogy. This radiation is only significant for black holes much less massive than stars—and none of these have been found. However, ‘Hawking radiation’ had very deep implications for mathematical physics—indeed one of the main achievements of string theory has been to corroborate his idea. It is still the focus of theoretical interest—a topic of debate and controversy more than 40 years after his discovery. Indeed the Harvard theorist, Andrew Strominger (with whom Stephen recently collaborated) said that this paper had caused ‘more sleepless nights among theoretical physicists than any paper in history.’ The key issue is whether information that is seemingly lost when objects fall into a black hole is in principle recoverable from the radiation when it evaporates. If it is not, this violates a deeply believed general physical principle. In 2013 he was one of the early winners of the Breakthrough Prize, worth 3 million dollars, which was intended to recognize theoretical work.

Cambridge was Stephen’s base throughout his career, and he became a familiar figure navigating his wheelchair around the city’s streets. By the end of the 1970s, he had advanced to one of the most distinguished posts in the University—the Lucasian Professorship of Mathematics, once held by Newton himself. He held this chair with distinction for 30 years; but reached the retiring age in 2009 and thereafter held a special research professorship. He travelled widely: he was an especially frequent visitor at Caltech, in Pasadena, California; and at Texas A&M University. He continued to seek new links between the very large (the cosmos) and the very small (atoms and quantum theory) and to gain deeper insights into the very beginning of our universe—addressing questions like ‘was our big bang the only one?’ He had a remarkable ability to figure things out in his head. But latterly he worked with students and colleagues who would write a formula on a blackboard; he would stare at it, and say whether he agreed with it, and perhaps what should come next.

In 1987, Stephen contracted pneumonia. He had to undergo a tracheotomy, which removed even the limited powers of speech he then possessed. It had been more than 10 years since he could write, or even  use a keyboard. Without speech, the only way he could communicate was by directing his eye towards  one of the letters of the alphabet on a big board in front of him.

But he was saved by technology. He still had the use of one hand; and a computer, controlled by a single lever, allowed him to spell out sentences. These were then declaimed by a speech synthesizer, with the androidal American accent that has since become his trademark. His lectures were, of course, pre-prepared, but conversation remained a struggle. Each word involved several presses of the lever, so even a sentence took several minutes. He learnt to economize with words. His comments were aphoristic or oracular, but often infused with wit. In his later years, he became too weak to control this machine effectively, even via facial muscles or eye movements, and his communication—to his immense frustration—became even slower.

At the time of his tracheotomy operation, he had a rough draft of a book, which he’d hoped would describe his ideas to a wide readership and earn something for his two eldest children, who were then of college age. On his recovery from pneumonia, he resumed work with the help of an editor. When the US edition of   A Brief History of Time appeared, the printers made some errors (a picture was upside down), and the publishers tried to recall the stock. To their amazement, all copies had already been sold. This was the first inkling that the book was destined for runaway success—four years on bestseller lists around the world.

The feature film The Theory of Everything (where he was superbly impersonated by Eddie Redmayne, in an Oscar-winning performance) portrayed  the human story behind his struggle. It surpassed most biopics in  representing the main characters so well that they themselves were happy with the portrayal (even though it understandably omitted and conflated key episodes in his scientific life). Even before this film, his life and work had featured in movies. In  an excellent TV docudrama made in 2004, he was played by Benedict Cumberbatch (In 2012 Cumberbatch spoke his words in a 4-part documentary The Grand Design made for the Discovery TV  Channel).

Why did he become such a ‘cult figure?’ The concept of an imprisoned mind roaming the cosmos plainly grabbed people’s imagination. If he had achieved equal distinction in (say) genetics rather than cosmology, his triumph of intellect against adversity probably wouldn’t have achieved the same resonance with a worldwide public.

The Theory of Everything conveyed with sensitivity how the need for support (first from a succession of students, but later requiring a team of nurses) strained his marriage to breaking point, especially when augmented by the pressure of his growing celebrity. Jane’s book, on which the film is based chronicles the 25 years during which, with amazing dedication, she underpinned his family life and his career.

This is where the film ends. But it left us only half way through Stephen’s adult life. After the split with Jane, Stephen married, in 1995, Elaine Mason, who had been one of his nurses, and whose former husband had designed Stephen’s speech synthesizer. But this partnership broke up within a decade. He was sustained, then and thereafter, by a team of helpers and personal assistants, as well as his family. His daughter Lucy has written books for children with her father as coauthor. His later theories were described, and beautifully illustrated, in other books such as Our Universe in a Nutshell and The Grand Design. These weren’t  bought by quite as many people as his first book—but probably more readers got to the end of them.

The success of A Brief History of Time catapulted Stephen to international stardom. He  featured in numerous TV programs; his lectures filled the Albert Hall, and similar venues in the US and Japan. He  featured in Star Trek and The Simpsons, and in numerous TV documentaries, as well as advertisements. He lectured at Clinton’s White House; he was back there more recently when President Obama presented him with the US Medal of Freedom, a very rare honor for any foreigner—and of course just one of the many awards he accumulated over his career (including Companion of Honor from the UK). In the summer of 2012, he reached perhaps his largest-ever audience when he had a star role at the opening ceremony of the London Paralympics.

His 60th birthday celebrations, in January 2002 , were a memorable occasion for all of us. Hundreds of leading scientists came from all over the world to honor and celebrate Stephen’s discoveries, and to spend a week discussing the latest theories on space, time, and the cosmos. But the celebrations weren’t just scientific—that wouldn’t have been Stephen’s style. Stephen was surrounded by his children and grandchildren; there was music and singing; there were ‘celebrities’ in attendance. And when the week’s events were all over, he celebrated with a trip in a hot air balloon.

It was amazing enough that Stephen reached the age of 60; few of us then thought that he would survive 16 more years. His 70th birthday was again marked by an international gathering of scientists in Cambridge, and also with some razzmatazz. So was his 75th birthday, though now shared by several million people via a livestream on the internet. He was in these last years plainly weakening. But he was still able to ‘deliver’ entertaining (and sometimes rather moving) lectures via his speech synthesizer and with the aid of skillfully prepared visuals.

Stephen continued, right until his last decade, to coauthor technical papers, and speak at premier international conferences—doubly remarkable in a subject where even healthy researchers tend to peak at an early age. Specially influential were his contributions to ‘cosmic inflation’—a theory that many believe describes the ultra-early phases of our expanding universe. A key issue is to understand the primordial seeds which eventually develop into galaxies. He proposed (as, independently, did the Russian theorist Viatcheslav Mukhanov) that these were quantum fluctuations—somewhat analogous to those involved in ‘Hawking radiation’ from black holes. He hosted an important meeting in 1982 where such ideas were thoroughly discussed. Subsequently, particularly with James Hartle and Thomas Hertog, he made further steps towards linking the two great theories of 20th century physics: the quantum theory of the microworld and Einstein’s theory of gravity and space-time.

He continued  to be an inveterate traveller—despite attempts to curb this as his respiration weakened. This wasn’t just to lecture. For instance, on a visit to Canada he was undeterred by having to go two miles down a mine-shaft to visit an underground laboratory where famous and delicate experiments had been done. And on a later trip, only a last-minute health setback prevented him from going to the Galapagos. All these travels—and indeed his everyday working life—involved an entourage of assistants and nurses. His fame, and the allure of his public appearances, gave him the resources for  nursing care, and protected him against the ‘does he take sugar?’ type of indignity that the disabled often suffer.

Stephen was far from being the archetype unworldly or nerdish scientist—his personality remained amazingly unwarped by his frustrations and handicaps. As well as his extensive travels, he enjoyed  trips to theatre or opera. He had robust common sense, and was ready to express forceful political opinions. However, a downside of his iconic status was that that his comments attracted exaggerated attention even on topics where he had  no special expertise—for instance philosophy, or the dangers from aliens or from intelligent machines. And he was sometimes involved in media events where his ‘script’ was written by the promoters of causes about which he may have been ambivalent.

But there was absolutely no gainsaying his lifelong commitment to campaigns for the disabled, and (just in the last few months) in support of the NHS—to which he acknowledged he owed so much. He was always, at the personal level, sensitive to the misfortunes of others. He recorded  that, when in hospital soon after his illness was first diagnosed, his depression was lifted when he compared his lot with a boy in the next bed who was dying of leukemia. And he was firmly aligned with other political campaigns and causes. When he visited Israel, he insisted on going also to the West Bank. Newspapers in 2006 showed remarkable pictures of him, in his wheelchair, surrounded  by fascinated and curious crowds in Ramallah.

Even more astonishing are the pictures of him ‘floating’ in the NASA aircraft  (the ‘vomit comet’) that allows passengers to experience weightlessness—he was manifestly overjoyed at escaping, albeit briefly, the clutches of the gravitational force he’d studied for decades and which had so cruelly imprisoned his body.

Tragedy struck Stephen Hawking when he was only 22. He was diagnosed with a deadly disease, and his  expectations dropped to zero. He himself said that everything that happened since then was a bonus. And what a triumph his life has been. His name will live in the annals of science; millions have had their cosmic horizons widened by his best-selling books; and even more, around the world, have been inspired by a unique example of achievement against all the odds—a manifestation of amazing will-power and determination.

Martin Rees is Astronomer Royal of Great Britain, a Fellow of Trinity College, Cambridge, a former director of the Cambridge Institute of Astronomy and author, most recently, of the bestselling Just Six Numbers: The Deep Forces That Shape the Universe. His forthcoming book, On the Future, will be available in October 2018.

Introducing Volume 15 of The Collected Papers of Albert Einstein

From fraudulent science to hope for European reunification, the newest volume of The Collected Papers of Albert Einstein conveys the breakneck speed of Einstein’s personal and professional life. Volume 15 will be out on April 6!

Volume 15: The Berlin Years
Writings & Correspondence, June 1925-May 1927, Documentary Edition

Edited by Diana Kormos Buchwald, József Illy, A. J. Kox, Dennis Lehmkuhl, Ze’ev Rosenkranz & Jennifer Nollar James

Princeton University Press, the Einstein Papers Project at the California Institute of Technology, and the Albert Einstein Archives at the Hebrew University of Jerusalem, are pleased to announce the latest volume in the authoritative COLLECTED PAPERS OF ALBERT EINSTEIN. This volume covers one of the most thrilling two-year periods in twentieth-century physics, as matrix mechanics—developed chiefly by W. Heisenberg, M. Born, and P. Jordan—and wave mechanics—developed by E. Schrödinger—supplanted earlier quantum theory. The almost one hundred writings, a third of which have never before been published, and the more than thirteen hundred letters demonstrate Einstein’s immense productivity at a tumultuous time.

Within this volume, Einstein grasps the conceptual peculiarities involved in the new quantum mechanics; falls victim to scientific fraud while in collaboration with E. Rupp; and continues his participation in the League of Nations’ International Committee on Intellectual Cooperation.


Every document in The Collected Papers of Albert Einstein appears in the language in which it was written, and this supplementary paperback volume presents the English translations of select portions of non-English materials in Volume 15. This translation does not include notes or annotation of the documentary volume and is not intended for use without the original language documentary edition which provides the extensive editorial commentary necessary for a full historical and scientific understanding of the documents.

Translated by Jennifer Nollar James, Ann M. Hentschel, and Mary Jane Teague, Andreas Aebi and Klaus Hentschel, consultants


Diana Kormos Buchwald, General Editor

THE COLLECTED PAPERS OF ALBERT EINSTEIN is one of the most ambitious publishing ventures ever undertaken in the documentation of the history of science.  Selected from among more than 40,000 documents contained in the personal collection of Albert Einstein (1879-1955), and 20,000 Einstein and Einstein-related documents discovered by the editors since the beginning of the Einstein Papers Project, The Collected Papers provides the first complete picture of a massive written legacy that ranges from Einstein’s first work on the special and general theories of relativity and the origins of quantum theory, to expressions of his profound concern with international cooperation and reconciliation, civil liberties, education, Zionism, pacifism, and disarmament.  The series will contain over 14,000 documents as full text and will fill close to thirty volumes.  Sponsored by the Hebrew University of Jerusalem and Princeton University Press, the project is located at and supported by the California Institute of Technology and has made available a monumental collection of primary material. It will continue to do so over the life of the project. The Albert Einstein Archives is located at the Hebrew University of Jerusalem. The open access digital edition of the first 15 volumes of the Collected Papers is available online at

ABOUT THE SERIES: Fifteen volumes covering Einstein’s life and work up to his forty-eighth birthday have so far been published. They present more than 500 writings and 7,000 letters written by and to Einstein. Every document in The Collected Papers appears in the language in which it was written, while the introduction, headnotes, footnotes, and other scholarly apparatus are in English.  Upon release of each volume, Princeton University Press also publishes an English translation of previously untranslated non-English documents.

ABOUT THE EDITORS: At the California Institute of Technology, Diana Kormos Buchwald is professor of history; A. J. Kox is senior editor and visiting associate in history; József Illy and Ze’ev Rosenkranz are editors and senior researchers in history; Dennis Lehmkuhl is research assistant professor and scientific editor; and Jennifer Nollar James is assistant editor.

Jeffrey Bub & Tanya Bub: There are recipes for Pi. But quantum mechanics?

There’s a recipe for Pi, in fact quite a few recipes. Here’s one that dates to the fifteenth century, discovered by the Indian mathematician and astronomer Nilakantha:


For the trillions of decimal places to which the digits have been calculated, each digit in the decimal expansion of Pi occurs about one-tenth of the time, each pair of digits about one-hundredth of the time, and so on. Its still a deep unsolved mathematical problem to prove that this is in fact a feature of Pi—that the digits will continue to be uniformly distributed in this sense as more and more digits are calculated—but the digits aren’t totally random, since there’s a recipe for calculating them.

Quantum mechanics supplies a recipe for calculating the probabilities of events, how likely it is for an event to happen, but the theory doesn’t say whether an individual event will definitely happen or not. So is quantum theory complete, as Einstein thought, in which case we should try to complete the theory by refining the recipe, or are the individual events really totally random?

Einstein didn’t like the idea that God plays dice with the universe, as he characterized the orthodox Copenhagen interpretation of quantum mechanics adopted by Niels Bohr, Werner Heisenberg, and colleagues. He wrote to his friend the physicist Max Born:

I find the idea quite intolerable that an electron exposed to radiation should choose of its own free will, not only its moment to jump off, but also its direction. In that case, I would rather be a cobbler, or even an employee in a gaming house, than a physicist.

But Einstein was wrong. Consider this puzzle. Could you rig pairs of coins according to some recipe so that if Alice and Bob, separated by any distance, each toss a coin from a rigged pair heads up, one coin lands heads and the other tails, but if they toss the coins any other way (both tails up, or one tails up and the other heads up), they land the same? It turns out that if each coin is designed to land in any way at all that does not depend on the paired coin or how the paired coin is tossed—if each coin has its own “being-thus,” as Einstein put it—you couldn’t get the correlation right for more than 75% of the tosses. This is a version of Bell’s theorem, proved by John Bell in 1964.


What has this got to do with quantum randomness? The coin correlation is actually a “superquantum” correlation called a PR-correlation, after Sandu Popescu and Daniel Rohrlich who came up with the idea. Quantum particles aren’t correlated in quite this way, but measurements on pairs of photons in an “entangled” quantum state can produce a correlation that is close to the coin correlation. If Alice and Bob use entangled photons rather than coins, they could simulate the coin correlation with a success rate of about 85% by measuring the polarizations of the photons in certain directions.

Suppose Alice measures the polarizations of her photons in direction A = 0 or A′ = π/4 instead of tossing her coin tails up or heads up, and Bob measures in the direction B = π/8 or B′ = −π/8 instead of tossing his coin tails up or heads up. Then the angle between Alice’s measurement direction and Bob’s measurement direction is π/8, except when Alice measures in the direction A′ and Bob measures in the direction B′, in which case the angle is 3π/8. According to the quantum recipe for probabilities, the probability that the photon polarizations are the same when they are measured in directions π/8 apart is cos2(π/8), and the probability that the photon polarizations are different when they are measured in directions 3π/8 apart is sin2(3π/8) = cos2(π/8). So the probability that Alice and Bob get outcomes + or − corresponding to heads or tails that mimic the coin correlation is cos2(π/8), which is approximately .85.

Bell’s theorem tells us that this pattern of measurement outcomes is closer to the coin correlation pattern than any possible recipe could produce. So God does play dice, and events involving entangled quantum particles are indeed totally random!

BubTanya Bub is founder of 48th Ave Productions, a web development company. She lives in Victoria, British Columbia. Jeffrey Bub is Distinguished University Professor in the Department of Philosophy and the Institute for Physical Science and Technology at the University of Maryland, where he is also a fellow of the Joint Center for Quantum Information and Computer Science. His books include Bananaworld: Quantum Mechanics for Primates. He lives in Washington, DC. They are the authors of Totally Random: Why Nobody Understands Quantum Mechanics (A Serious Comic on Entanglement).

Celebrate Pi Day with Books about Einstein

Pi Day is coming up! Mathematicians around the world celebrate on March 14th because the date represents the first three digits of π: 3.14.

In Princeton, Pi Day is a huge event even for the non-mathematicians among us, given that March 14 is also Albert Einstein’s birthday. Einstein was born on March 14, 1879, in Ulm, in the German Empire. He turns 139 this year! If you’re in the Princeton area and want to celebrate, check out some of the festivities happening around town:

Saturday, 3/10/18

  • Apple Pie Eating Contest, 9:00 a.m., McCaffrey’s (301 North Harrison Street). Arrive by 8:45 a.m. to participate.
  • Einstein in Princeton Guided Walking Tour, 10:00 a.m. Call Princeton Tour Company at (855) 743-1415 for details.
  • Einstein Look-A-Like Contest, 12:00 p.m., Nassau Inn. Arrive early to get a spot to watch this standing-room-only event!
  • Pi Recitation Contest, 1:30 p.m., Prince William Ballroom, Nassau Inn. Children ages 12 and younger may compete. Register by 1:15 p.m.
  • Pie Throwing Event, 3:14 p.m., Palmer Square. Proceeds to benefit the Princeton Educational Fund Teacher Mini-Grant Program.
  • Cupcake Decorating Competition, 4:00 p.m., House of Cupcakes (34 Witherspoon Street). The winner receives one free cupcake each month for the rest of the year.

Wednesday, 3/14/18

  • Princeton School Gardens Cooperative Fundraiser, 12:00 p.m. to 6:00 p.m., The Bent Spoon (35 Palmer Square West) and Lillipies (301 North Harrison Street). All proceeds from your afternoon treat will be donated to the Princeton School Gardens Cooperative.
  • Pi Day Pop Up Wedding/Vow Renewal Ceremonies, 3:14 p.m. to 6:00 p.m., Princeton Pi (84 Nassau Street). You must pre-register by contacting the Princeton Tour Company.

Not into crowds, or pie? You can also celebrate this multifaceted holiday by picking up one of PUP’s many books about Albert Einstein! In 1922, Princeton University Press published Einstein’s The Meaning of Relativity, his first book produced by an American publisher. Since then, we’ve published numerous works by and about Einstein.

The books and collections highlighted here celebrate not only his scientific accomplishments but also his personal reflections and his impact on present-day scholarship and technology. Check them out and learn about Einstein’s interpersonal relationships, his musings on travel, his theories of time, and his legacy for the 21st century.

Volume 15 of the Collected Papers of Albert Einstein, forthcoming in April 2018, covers one of the most thrilling two-year periods in twentieth-century physics, as matrix mechanics—developed chiefly by W. Heisenberg, M. Born, and P. Jordan—and wave mechanics—developed by E. Schrödinger—supplanted the earlier quantum theory. The almost one hundred writings by Einstein, of which a third have never been published, and the more than thirteen hundred letters show Einstein’s immense productivity and hectic pace of life.

Einstein quickly grasps the conceptual peculiarities involved in the new quantum mechanics, such as the difference between Schrödinger’s wave function and a field defined in spacetime, or the emerging statistical interpretation of both matrix and wave mechanics. Inspired by correspondence with G. Y. Rainich, he investigates with Jakob Grommer the problem of motion in general relativity, hoping for a hint at a new avenue to unified field theory.

Readers can access Volumes 1-14 of the Collected Papers of Albert Einstein online at The Digital Einstein Papers, an exciting new free, open-access website that brings the writings of the twentieth century’s most influential scientist to a wider audience than ever before. This unique, authoritative resource provides full public access to the complete transcribed, annotated, and translated contents of each print volume of the Collected Papers. The volumes are published by Princeton University Press, sponsored by the Hebrew University of Jerusalem, and supported by the California Institute of Technology. Volumes 1-14 of The Collected Papers cover the first forty-six years of Einstein’s life, up to and including the years immediately before the final formulation of new quantum mechanics. The contents of each new volume will be added to the website approximately eighteen months after print publication. Eventually, the website will provide access to all of Einstein’s writings and correspondence accompanied by scholarly annotation and apparatus, which are expected to fill thirty volumes.

The Travel Diaries of Albert Einstein is the first publication of Albert Einstein’s 1922 travel diary to the Far East and Middle East, regions that the renowned physicist had never visited before. Einstein’s lengthy itinerary consisted of stops in Hong Kong and Singapore, two brief stays in China, a six-week whirlwind lecture tour of Japan, a twelve-day tour of Palestine, and a three-week visit to Spain. This handsome edition makes available, for the first time, the complete journal that Einstein kept on this momentous journey.

The telegraphic-style diary entries—quirky, succinct, and at times irreverent—record Einstein’s musings on science, philosophy, art, and politics, as well as his immediate impressions and broader thoughts on such events as his inaugural lecture at the future site of the Hebrew University in Jerusalem, a garden party hosted by the Japanese Empress, an audience with the King of Spain, and meetings with other prominent colleagues and statesmen. Entries also contain passages that reveal Einstein’s stereotyping of members of various nations and raise questions about his attitudes on race. This beautiful edition features stunning facsimiles of the diary’s pages, accompanied by an English translation, an extensive historical introduction, numerous illustrations, and annotations. Supplementary materials include letters, postcards, speeches, and articles, a map of the voyage, a chronology, a bibliography, and an index.

Einstein would go on to keep a journal for all succeeding trips abroad, and this first volume of his travel diaries offers an initial, intimate glimpse into a brilliant mind encountering the great, wide world. 

More than fifty years after his death, Albert Einstein’s vital engagement with the world continues to inspire others, spurring conversations, projects, and research, in the sciences as well as the humanities. Einstein for the 21st Century shows us why he remains a figure of fascination.

In this wide-ranging collection, eminent artists, historians, scientists, and social scientists describe Einstein’s influence on their work, and consider his relevance for the future. Scientists discuss how Einstein’s vision continues to motivate them, whether in their quest for a fundamental description of nature or in their investigations in chaos theory; art scholars and artists explore his ties to modern aesthetics; a music historian probes Einstein’s musical tastes and relates them to his outlook in science; historians explore the interconnections between Einstein’s politics, physics, and philosophy; and other contributors examine his impact on the innovations of our time. Uniquely cross-disciplinary, Einstein for the 21st Century serves as a testament to his legacy and speaks to everyone with an interest in his work. 

The contributors are Leon Botstein, Lorraine Daston, E. L. Doctorow, Yehuda Elkana, Yaron Ezrahi, Michael L. Friedman, Jürg Fröhlich, Peter L. Galison, David Gross, Hanoch Gutfreund, Linda D. Henderson, Dudley Herschbach, Gerald Holton, Caroline Jones, Susan Neiman, Lisa Randall, Jürgen Renn, Matthew Ritchie, Silvan S. Schweber, and A. Douglas Stone.

On April 6, 1922, in Paris, Albert Einstein and Henri Bergson publicly debated the nature of time. Einstein considered Bergson’s theory of time to be a soft, psychological notion, irreconcilable with the quantitative realities of physics. Bergson, who gained fame as a philosopher by arguing that time should not be understood exclusively through the lens of science, criticized Einstein’s theory of time for being a metaphysics grafted on to science, one that ignored the intuitive aspects of time. Jimena Canales tells the remarkable story of how this explosive debate transformed our understanding of time and drove a rift between science and the humanities that persists today.

The Physicist and the Philosopher is a magisterial and revealing account that shows how scientific truth was placed on trial in a divided century marked by a new sense of time.


After completing the final version of his general theory of relativity in November 1915, Albert Einstein wrote a book about relativity for a popular audience. His intention was “to give an exact insight into the theory of relativity to those readers who, from a general scientific and philosophical point of view, are interested in the theory, but who are not conversant with the mathematical apparatus of theoretical physics.” The book remains one of the most lucid explanations of the special and general theories ever written.

This new edition features an authoritative English translation of the text along with an introduction and a reading companion by Hanoch Gutfreund and Jürgen Renn that examines the evolution of Einstein’s thinking and casts his ideas in a broader present-day context.

Published on the hundredth anniversary of general relativity, this handsome edition of Einstein’s famous book places the work in historical and intellectual context while providing invaluable insight into one of the greatest scientific minds of all time.


Browse Our 2018 Physics & Astrophysics Catalog

Our new Physics & Astrophysics catalog includes two new graduate-level textbooks from Kip S. Thorne, Co-Winner of the 2017 Noble Prize in Physics, as well as a look into the physics behind black holes.

If you plan on attending AAS 2018 in National Harbor, MD this weekend, please stop by Booth 1003 to see our full range of Physics and Astrophysics titles and more.

Black holes, predicted by Albert Einstein’s general theory of relativity more than a century ago, have long intrigued scientists and the public with their bizarre and fantastical properties. Although Einstein understood that black holes were mathematical solutions to his equations, he never accepted their physical reality—a viewpoint many shared. This all changed in the 1960s and 1970s, when a deeper conceptual understanding of black holes developed just as new observations revealed the existence of quasars and X-ray binary star systems, whose mysterious properties could be explained by the presence of black holes. Black holes have since been the subject of intense research—and the physics governing how they behave and affect their surroundings is stranger and more mind-bending than any fiction.

The Little Book of Black Holes takes readers deep into the mysterious heart of the subject, offering rare clarity of insight into the physics that makes black holes simple yet destructive manifestations of geometric destiny.

Modern Classical Physics is a long-awaited, first-year, graduate-level text and reference book covers the fundamental concepts and twenty-first-century applications of six major areas of classical physics that every masters- or PhD-level physicist should be exposed to, but often isn’t: statistical physics, optics (waves of all sorts), elastodynamics, fluid mechanics, plasma physics, and special and general relativity and cosmology. Growing out of a full-year course that the eminent researchers Kip Thorne and Roger Blandford taught at Caltech for almost three decades, this book is designed to broaden the training of physicists. Its six main topical sections are also designed so they can be used in separate courses, and the book provides an invaluable reference for researchers.

First published in 1973, Gravitation is a landmark graduate-level textbook that presents Einstein’s general theory of relativity and offers a rigorous, full-year course on the physics of gravitation. Upon publication, Science called it “a pedagogic masterpiece,” and it has since become a classic, considered essential reading for every serious student and researcher in the field of relativity. This authoritative text has shaped the research of generations of physicists and astronomers, and the book continues to influence the way experts think about the subject.

Steven S. Gubser: Thunder and Lightning from Neutron Star mergers

As of late 2015, we have a new way of probing the cosmos: gravitational radiation. Thanks to LIGO (the Laser Interferometer Gravitational-wave Observatory) and its new sibling Virgo (a similar interferometer in Italy), we can now “hear” the thumps and chirps of colliding massive objects in the universe. Not for nothing has this soundtrack been described by LIGO scientists as “the music of the cosmos.” This music is at a frequency easily discerned by human hearing, from somewhat under a hundred hertz to several hundred hertz. Moreover, gravitational radiation, like sound, is wholly different from light. It is possible for heavy dark objects like black holes to produce mighty gravitational thumps without at the same time emitting any significant amount of light. Indeed, the first observations of gravitational waves came from black hole merger events whose total power briefly exceeded the light from all stars in the known universe. But we didn’t observe any light from these events at all, because almost all their power went into gravitational radiation.

In August 2017, LIGO and Virgo observed a collision of neutron stars which did produce observable light, notably in the form of gamma rays. Think of it as cosmic thunder and lightning, where the thunder is the gravitational waves and the lightning is the gamma rays. When we see a flash of ordinary lightning, we can count a few seconds until we hear the thunder. Knowing that sound travels one mile in about five seconds, we can reckon how distant the event is. The reason this method works is that light travels much faster than sound, so we can think of the transmission of light as instantaneous for purposes of our estimate.

Things are very different for the neutron star collision, in that the event took place about 130 million light years away, but the thunder and lightning arrived on earth pretty much simultaneously. To be precise, the thunder was first: LIGO and Virgo heard a basso rumble rising to a characteristic “whoop,” and just 1.7 seconds later, the Fermi and INTEGRAL experiments observed gamma ray bursts from a source whose location was consistent with the LIGO and Virgo observations. The production of gamma rays from merging neutron stars is not a simple process, so it’s not clear to me whether we can pin that 1.7 seconds down as a delay precisely due to the astrophysical production mechanisms; but at least we can say with some confidence that the propagation time of light and gravity waves are the same to within a few seconds over 130 million light years. From a certain point of view, that amounts to one of the most precise measurements in physics: the ratio of the speed of light to the speed of gravity equals 1, correct to about 14 decimal places or better.

The whole story adds up much more easily when we remember that gravitational waves are not sound at all. In fact, they’re nothing like ordinary sound, which is a longitudinal wave in air, where individual air molecules are swept forward and backward just a little as the sound waves pass them by. Gravitational waves instead involve transverse disturbances of spacetime, where space is stretched in one direction and squeezed in another—but both of those stretch-squeeze directions are at right angles to the direction of the wave. Light has a similar transverse quality: It is made up of electric and magnetic fields, again in directions that are at right angles to the direction in which the light travels. It turns out that a deep principle underlying both Maxwell’s electromagnetism and Einstein’s general relativity forces light and gravitational waves to be transverse. This principle is called gauge symmetry, and it also guarantees that photons and gravitons are massless, which implies in turn that they travel at the same speed regardless of wavelength.

It’s possible to have transverse sound waves: For instance, shearing waves in crystals are a form of sound. They typically travel at a different speed from longitudinal sound waves. No principle of gauge symmetry forbids longitudinal sound waves, and indeed they can be directly observed, along with their transverse cousins, in ordinary materials like metals. The gauge symmetries that forbid longitudinal light waves and longitudinal gravity waves are abstract, but a useful first cut at the idea is that there is extra information in electromagnetism and in gravity, kind of like an error-correcting code. A much more modest form of symmetry is enough to characterize the behavior of ordinary sound waves: It suffices to note that air (at macroscopic scales) is a uniform medium, so that nothing changes in a volume of air if we displace all of it by a constant distance.

In short, Maxwell’s and Einstein’s theories have a feeling of being overbuilt to guarantee a constant speed of propagation. And they cannot coexist peacefully as theories unless these speeds are identical. As we continue Einstein’s hunt for a unified theory combining electromagnetism and gravity, this highly symmetrical, overbuilt quality is one of our biggest clues.

The transverse nature of gravitational waves is immediately relevant to the latest LIGO / Virgo detection. It is responsible for the existence of blind spots in each of the three detectors (LIGO Hanford, LIGO Livingston, and Virgo). It seems like blind spots would be bad, but they actually turned out to be pretty convenient: The signal at Virgo was relatively weak, indicating that the direction of the source was close to one of its blind spots. This helped localize the event, and localizing the event helped astronomers home in on it with telescopes. Gamma rays were just the first non-gravitational signal observed: the subsequent light-show from the death throes of the merging neutron stars promises to challenge and improve our understanding of the complex astrophysical processes involved. And the combination of gravitational and electromagnetic observations will surely be a driver of new discoveries in years and decades to come.


BlackSteven S. Gubser is professor of physics at Princeton University and the author of The Little Book of String TheoryFrans Pretorius is professor of physics at Princeton. They both live in Princeton, New Jersey. They are the authors of The Little Book of Black Holes.

Steven S. Gubser & Frans Pretorius: The Little Book of Black Holes

Black holes, predicted by Albert Einstein’s general theory of relativity more than a century ago, have long intrigued scientists and the public with their bizarre and fantastical properties. Although Einstein understood that black holes were mathematical solutions to his equations, he never accepted their physical reality—a viewpoint many shared. This all changed in the 1960s and 1970s, when a deeper conceptual understanding of black holes developed just as new observations revealed the existence of quasars and X-ray binary star systems, whose mysterious properties could be explained by the presence of black holes. Black holes have since been the subject of intense research—and the physics governing how they behave and affect their surroundings is stranger and more mind-bending than any fiction. The Little Book of Black Holes by Steven S. Gubser and Frans Pretorius takes readers deep into the mysterious heart of the subject, offering rare clarity of insight into the physics that makes black holes simple yet destructive manifestations of geometric destiny. Read on to learn a bit more about black holes and what inspired the authors to write this book.

Your book tells the story of black holes from a physics perspective. What are black holes, really? What’s inside?

Black holes are regions of spacetime from which nothing can escape, not even light. In our book, we try to live up to our title by getting quickly to the heart of the subject, explaining in non-technical terms what black holes are and how we use Einstein’s theory of relativity to understand them. What’s inside black holes is a great mystery. Taken at face value, general relativity says spacetime inside a black hole collapses in on itself, so violently that singularities form. We need something more than Einstein’s theory of relativity to understand what these singularities mean. Hawking showed that quantum effects cause black holes to radiate very faintly. That radiation is linked with quantum fluctuations inside the black hole. But it’s a matter of ongoing debate whether these fluctuations are a key to resolving the puzzle of the singularity, or whether some more drastic theory is needed.

How sure are we that black holes exist?

A lot more certain than we were a few years ago. In September 2015, the LIGO experiment detected gravitational waves from the collision of two black holes, each one about thirty times the mass of the sun. Everything about that detection fit our expectations based on Einstein’s theories, so it’s hard to escape the conclusion that there really are black holes out there. In fact, before the LIGO detection we were already pretty sure that black holes exist. Matter swirling around gigantic black holes at the core of distant galaxies form the brightest objects in the Universe. They’re called quasars, and the only reason they’re dim in our sight is that they’re so far away, literally across the Universe. Similar effects around smaller black holes generate X-rays that we can detect relatively nearby, mere thousands of light years away from us. And we have good evidence that there is a large black hole at the center of the Milky Way.

Can you talk a bit about the formation of black holes?

Black holes with mass comparable to the sun can form when big stars run out of fuel and collapse in on themselves. Ordinarily, gravity is the weakest force, but when too much matter comes together, no force conceivable can hold it up against the pull of gravity. In a sense, even spacetime collapses when a black hole forms, and the result is a black hole geometry: an endless inward cascade of nothing into nothing. All the pyrotechnics that we see in distant quasars and some nearby X-ray sources comes from matter rubbing against itself as it follows this inward cascade.

How have black holes become so interesting to non-specialists? How have they been glorified in popular culture?

There’s so much poetry in black hole physics. Black hole horizons are where time stands still—literally! Black holes are the darkest things that exist in Nature, formed from the ultimate ashes of used-up stars. But they create brilliant light in the process of devouring yet more matter. The LIGO detection was based on a black hole collision that shook the Universe, with a peak power greater than all stars combined; yet we wouldn’t even have noticed it here on earth without the most exquisitely sensitive detector of spacetime distortions ever built. Strangest of all, when stripped of surrounding matter, black holes are nothing but empty space. Their emptiness is actually what makes them easy to understand mathematically. Only deep inside the horizon does the emptiness end in a terrible, singular core (we think). Horrendous as this sounds, black holes could also be doorways into wormholes connecting distant parts of the Universe. But before packing our bags for a trip from Deep Space Nine to the Gamma Quadrant, we’ve got to read the fine print: as far as we know, it’s impossible to make a traversable wormhole.

What inspired you to write this book? Was there a point in life where your interest in this topic was piqued?

We both feel extremely fortunate to have had great mentors, including Igor Klebanov, Curt Callan, Werner Israel, Matthew Choptuik, and Kip Thorne who gave us a lot of insight into black holes and general relativity. And we owe a big shout-out to our editor, Ingrid Gnerlich, who suggested that we write this book.

GubserSteven S. Gubser is professor of physics at Princeton University and the author of The Little Book of String Theory. Frans Pretorius is professor of physics at Princeton.

Kip Thorne & Roger Blandford on Modern Classical Physics

PhysicsThis first-year, graduate-level text and reference book covers the fundamental concepts and twenty-first-century applications of six major areas of classical physics that every masters- or PhD-level physicist should be exposed to, but often isn’t: statistical physics, optics (waves of all sorts), elastodynamics, fluid mechanics, plasma physics, and special and general relativity and cosmology. Growing out of a full-year course that the eminent researchers Kip S. Thorne, winner of the 2017 Nobel Prize in Physics, and Roger D. Blandford taught at Caltech for almost three decades, this book is designed to broaden the training of physicists. Its six main topical sections are also designed so they can be used in separate courses, and the book provides an invaluable reference for researchers.

This book emerged from a course you both began teaching nearly 4 decades ago. What drove you to create the course, and ultimately to write this book?

KST: We were unhappy with the narrowness of physics graduate education in the United States. We believed that every masters-level or PhD physicist should be familiar with the basic concepts of all the major branches of classical physics and should have some experience applying them to real world phenomena. But there was no obvious route to achieve this, so we created our course.

RDB: Of course we had much encouragement from colleagues who helped us teach it and students who gave us invaluable feedback on the content.

The title indicates that the book is a “modern” approach to classical physics (which emphasizes physical phenomena at macroscopic scales). What specifically is “modern” in your book’s approach to this subject?

KST: Classical-physics ideas and tools are used extensively today in research areas as diverse as astrophysics, high-precision experimental physics, optical physics, biophysics, controlled fusion, aerodynamics, computer simulations, etc. Our book draws applications from all these modern topics and many more. Also, these modern applications have led to powerful new viewpoints on the fundamental concepts of classical physics, viewpoints that we elucidate—for example, quantum mechanical viewpoints and language for purely classical mode-mode coupling in nonlinear optics and in nonlinear plasma physics.

Why do you feel that it is so important for readers to become more familiar with classical physics, beyond what they may have been introduced to already?

KST: In their undergraduate and graduate level education, most physicists have been exposed to classical mechanics, electromagnetic theory, elementary thermodynamics, and little classical physics beyond this. But in their subsequent careers, most physicists discover that they need an understanding of other areas of classical physics (and this book is a vehicle for that).

In many cases they may not even be aware of their need. They encounter problems in their research or in R&D where powerful solutions could be imported from other areas of classical physics, if only they were aware of those other areas. An example from my career: in the 1970s, when trying to understand recoil of a binary star as it emits gravitational waves, I, like many relativity physicists before me, got terribly confused. Then my graduate student, Bill Burke—who was more broadly educated than I—said “we can resolve the confusion by adopting techniques that are used to analyze boundary layers in fluid flows around bodies with complicated shapes.” Those techniques (matched asymptotic expansions), indeed, did the job, and through Bill, they were imported from fluid mechanics into relativity.

RDB: Yes. To give a second example, when I was thinking about ways to accelerate cosmic rays, I recalled graduate lectures on stellar dynamics and found just the tools I needed.

You also mention in the book that geometry is a deep theme and important connector of ideas. Could you explain your perspective, and how geometry is used thematically throughout the book?

KST: The essential point is that, although coordinates are a powerful, and sometimes essential, tool in many calculations, the fundamental laws of physics can be expressed without the aid of coordinates; and, indeed, their coordinate-free expressions are generally elegant and exceedingly powerful. By learning to think about the laws in coordinate-free (geometric) language, a physicist acquires great power. For example, when one searches for new physical laws, requiring that they be geometric (coordinate-free) constrains enormously the forms that they may take. And in many practical computations (for example, of the relativistic Doppler shift), a geometric route to the solution can be faster and much more insightful than one that uses coordinates. Our book is infused with this.

RDB: We are especially keen on presenting these fundamental laws in a manner which makes explicit the geometrically formulated conservation laws for mass, momentum, energy, etc. It turns out that this is often a good starting point when one wants to solve these equations numerically. But ultimately, a coordinate system must be introduced to execute the calculations and interpret the output.

One of the areas of application that you cover in the book is cosmology, an area of research that has undergone a revolution over the past few decades. What are some of the most transformative discoveries in the field’s recent history? How does classical physics serve to underpin our modern understanding of how the universe formed and is evolving? What are some of the mysteries that continue to challenge scientists in the field of cosmology?   

RDB: There have indeed been great strides in understanding the large scale structure and evolution of the universe, and there is good observational support for a comparatively simple description. Cosmologists have found that 26 percent of the energy density in the contemporary, smoothed-out universe is in the form of “dark matter,” which only seems to interact through its gravity. Meanwhile, 69 percent is associated with a “cosmological constant,” as first introduced by Einstein and which causes the universe to accelerate. The remaining five percent is the normal baryonic matter which we once thought accounted for essentially all of the universe. The actual structure that we observe appears to be derived from almost scale-free statistically simple, random fluctuations just as expected from an early time known as inflation. Fleshing out the details of this description is almost entirely an exercise in classical physics. Even if this description is validated by future observations, much remains to be understood, including the nature of dark matter and the cosmological constant, what fixes the normal matter density, and the great metaphysical question of what lies beyond the spacetime neighborhood that we can observe directly.

KST: Remarkably, in fleshing out the details in the last chapter of our book, we utilize classical-physics concepts and results from every one of the other chapters. ALL of classical physics feeds into cosmology!

The revolution in cosmology that you describe depends upon many very detailed observations using telescopes operating throughout the entire electromagnetic spectrum and beyond. How do you deal with this in the book?

RDB: We make no attempt to describe the rich observational and experimental evidence, referring the reader to many excellent texts on cosmology that describe these in detail. However, we do describe some of the principles that underlie the design and operation of the radio and optical telescopes that bring us cosmological data.

There is has also been a lot of excitement regarding the recent observation by LIGO of gravitational waves caused by merging black holes. How is this subject covered in the book, and how, briefly, are some of the concepts of classical physics elucidated in your description of this cutting-edge research area?   

KST: LIGO’s gravitational wave detectors rely on an amazingly wide range of classical physics concepts and tools, so time and again we draw on LIGO for illustrations. The theory of random processes, spectral densities, the fluctuation-dissipation theorem, the Fokker-Planck equation; shot noise, thermal noise, thermoelastic noise, optimal filters for extracting weak signals from noise; paraxial optics, Gaussian beams, the theory of coherence, squeezed light, interferometry, laser physics; the interaction of gravitational waves with light and with matter; the subtle issue of the conservation or non conservation of energy in general relativity—all these and more are illustrated by LIGO in our book.

What are some of the classical physics phenomena in every day life that you are surprised more people do not fully understand—whether they are lay people, students, or scientists?

KST: Does water going down a drain really have a strong preference for clockwise in the northern hemisphere and counterclockwise in the south? How strong? What happens as you cross the equator? How are ocean waves produced? Why do stars twinkle in the night sky, and why doesn’t Jupiter twinkle? How does a hologram work? How much can solid objects be stretched before they break, and why are there such huge differences from one type of solid (for example thin wire) to another (a rubber band)?

RDB: I agree and have to add that I am regularly humbled by some every day phenomenon that I cannot explain or for which I have carried around for years a fallacious explanation. There is, rightly, a lot of focus right now on climate change, energy, hurricanes, earthquakes, and so on. We hear about them every day. We physicists need to shore up our understanding and do a better job of communicating this.

Do you believe that some of your intended readers might be surprised to discover the deep relevance of classical physics to certain subject areas?

KST: In subjects that physicists think of as purely quantum, classical ideas and classical computational techniques can often be powerful. Condensed matter physics is an excellent example—and accordingly, our book includes a huge number of condensed-matter topics. Examples are Bose-Einstein condensates, the van der Waals gas, and the Ising model for ferromagnetism.

RDB: Conversely, quantum mechanical techniques are often used to simplify purely classical problems, for example in optics.

Writing a book is always an intellectual journey. In the preparation of this tremendously wide-ranging book, what were some of the most interesting things you learned along the way?

KST: How very rich and fascinating is the world of classical physics—far more so than we thought in 1980 when we embarked on this venture. And then there are the new inventions, discoveries, and phenomena that did not exist in 1980 but were so important or mind-boggling that we could not resist including them in our book. For example, optical-frequency combs and the phase-locked lasers that underlie them, Bose-Einstein condensates, the collapse of the World Trade Center buildings on 9/11/01, the discovery of gravitational waves and the techniques that made it possible, laser fusion, and our view of the universe at large.

Kip S. Thorne is the Feynman Professor Emeritus of Theoretical Physics at Caltech. His books include Gravitation and Black Holes and Time Warps. Roger D. Blandford is the Luke Blossom Professor of Physics and the founding director of the Kavli Institute of Particle Astrophysics and Cosmology at Stanford University. Both are members of the National Academy of Sciences.


Read like a Nobel Prize-winning physicist

This morning Princeton University Press was thrilled to congratulate PUP author and celebrated physicist Kip Thorne on being a co-winner of the Nobel Prize in Physics for 2017. Dr. Thorne’s research has focused on Einstein’s general theory of relativity and astrophysics, with emphasis on relativistic stars, black holes, and especially gravitational waves. The latter observation, made in September 2015, validated a key prediction of Einstein’s general theory of relativity. Princeton University Press is honored to be the publisher of Dr. Thorne’s Modern Classical Physics, co-authored with Roger Blandford, and the new hardback edition of the renowned classic, Gravitation, co-authored with Charles Misner and the late John Wheeler, forthcoming this fall.

Over the years, we’ve published several Nobel winners, including:

  • Einstein
  • Richard Feynman (QED)
  • P.W. Anderson (the classic and controversial Theory of Superconductivity in the High-Tc Cuprates)
  • Paul Dirac (General Theory of Relativity)
  • Werner Heisenberg (Encounters with Einstein)

Interested in learning more about physics yourself? We put together the ultimate Nobel reading list. Click the graphic for links to each book.

PUP congratulates Kip S. Thorne, joint winner of the Nobel Prize in Physics

New Books Gravitation and Modern Classical Physics Publishing in October 2017

Princeton, NJ, October 3, 2017—Upon today’s announcement that Dr. Kip S. Thorne is the joint winner of the Nobel Prize in Physics for 2017, Princeton University Press would like to extend hearty congratulations to the celebrated physicist.

The Royal Swedish Academy recognizes Dr. Thorne, along with Rainer Weiss and Barry C. Barish, for decisive contributions to the LIGO detector and the observation of gravitational waves”.

Feynman Professor of Theoretical Physics, Emeritus at the California Institute of Technology, Dr. Thorne has focused his research on Einstein’s general theory of relativity and on astrophysics, with emphasis on relativistic stars, black holes, and especially gravitational waves. The latter observation, made in September 2015, validated a key prediction of Einstein’s general theory of relativity.

Princeton University Press is honored to be the publisher of Dr. Thorne’s Modern Classical Physics, co-authored with Roger Blandford, and the new hardback edition of the renowned classic, Gravitation, co-authored with Charles Misner and the late John Wheeler, publishing in October 2017.

According to Christie Henry, director of Princeton University Press, “Dr. Thorne’s creativity and brilliance have been as grounding to Princeton University Press’s publishing program in the physical sciences as gravitation is to the human experience.  His recently released Princeton University Press contributions, Gravitation and Modern Classical Physics, are vital to our mission of illuminating spheres of knowledge to advance and enrich the human conversation, and today we celebrate his commitment to science with the Nobel committee and readers across the universe.”

Since the publication of Albert Einstein’s The Meaning of Relativity in 1922, Princeton University Press has remained committed to publishing global thought leaders in the sciences and beyond. We are honored to count Dr. Thorne’s work as part of this legacy.


For more information, please contact:

Julia Haav, Assistant Publicity Director, 609.258.2831


Michael Strauss: America’s Eclipse

Welcome to the UniverseOn Monday, August 21, people all across the United States will witness one of the rarest and most spectacular of all astronomical phenomena: a total solar eclipse. This occurs when the position of the Moon and the Sun in the sky align perfectly, such that the Moon’s shadow falls onto a specific point on the Earth’s surface. If you are lucky enough to be standing in the shadow, you will see the Sun’s light completely blocked by the Moon: the sky will become dark, and the stars and planets will become visible. But because the apparent sizes of the Moon and the Sun are almost the same, and because everything is in motion—the Moon orbits Earth, and Earth rotates around its axis and orbits the Sun—the Moon’s shadow moves quickly.  During the eclipse, the Moon’s shadow will cross the United States at a speed of 1800 miles per hour, taking about 90 minutes to travel from the Pacific Coast in Oregon to touch the Atlantic in South Carolina.  This means that totality, the time when the Sun’s disk is completely covered as seen from any given spot along the eclipse path, is very brief: 2 minutes and 40 seconds at best.

If you are standing along the eclipse path, it takes about 2.5 hours for the Moon to pass across the Sun.  That is, you will see the disk of the Sun eaten away, becoming an ever-narrowing crescent. During this time, you can only look at the Sun with eclipse glasses (make sure they are from a reputable company!), which block the vast majority of the light from the Sun.  It is also fun to look at the dappled shadows underneath a leafy tree; if you look closely, you’ll see that the individual spots of light are all crescent-shaped. A bit more than an hour after the Moon begins to cover the Sun, you reach the point of totality, and the sky becomes dark. It is now safe to remove your eclipse glasses.

Experiencing a few minutes of darkness in the middle of the day is pretty cool. But what makes the eclipse really special is that with the light of the Sun’s disk blocked out, the faint outer atmosphere of the Sun, its corona, becomes visible to the naked eye. The corona consists of tenuous gas extending over millions of miles, with a temperature of a few million degrees. It is shaped by the complex magnetic field of the Sun, and may exhibit a complex arrangement of loops and filaments: indeed, observations of the solar corona during eclipses have been one of the principal ways in which astronomers have learned about its magnetic field. The sight is awe-inspiring; those who have experienced it say that it is as a life-changing experience.

As the Moon starts to move off the disk, the full brightness of the Sun becomes visible again, and you must put your eclipse glasses back on to protect your eyes. The Sun now appears as a narrow and ever-widening crescent. A bit more than an hour later, the Sun’s disk is completely uncovered.

The shadow of the Moon will be about 70 miles in diameter at any given time. That means that if you are not standing in that 70-mile-wide path as the shadow crosses the country, you will only see a partial solar eclipse, in which you will see the Sun appearing as a crescent.  Again, be sure to wear eclipse glasses to look at the Sun!

Solar eclipses happen roughly once or twice a year somewhere on Earth’s surface, but because  of the narrowness of the eclipse path, the number of people standing in the path is usually relatively small. This one, crossing the entire continental US, is special in this regard: tens of millions of people live within a few hours of the eclipse path. This promises to be the most widely seen and recorded eclipse in history! I have never seen a total eclipse of the Sun before, and am very excited to be traveling with my family to Oregon, where we have our fingers crossed for good weather. So, to all those who have the opportunity to stand in the Moon’s shadow, get yourself a pair of eclipse glasses, and prepare yourself to be awed.

Michael A. Strauss is professor of astrophysics at Princeton University. He is the coauthor (with Neil deGrasse Tyson and J. Richard Gott) of Welcome to the Universe: An Astrophysical Tour.

Anna Frebel: Solar Eclipse 2017

Next Monday, the U.S. will witness an absolutely breathtaking natural spectacle. One worthy of many tweets as it is of the astronomical kind—quite literally. I’m talking about the upcoming total solar eclipse where, for a short couple of minutes, the Moon will move directly into our line of sight to perfectly eclipse the Sun.

During the so-called “totality,” when the Sun is fully covered, everything around you will take on twilight colors. It will get cooler, the birds will become quieter, and you’ll get this eerie feeling that something is funny is going on. No wonder that in ancient times, people thought the world would end during such an event.

I have witnessed this twice before. 1999 in Munich, Germany, and 2002 in Ceduna, Australia. Like so many others, I traveled there with great anticipation to see the Sun disappear on us. In both cases, however, it was cloudy for hours before totality which caused frustration and even anxiety in the crowd. But nature happened to be kind. A few minutes before totality, the clouds parted to let us catch a glimpse. We experienced how the disk of the Sun finally fully vanished just after seeing the last little rays of light peeking through that produced a famous “diamond ring” image. We could also see the glowing corona surrounding the black Sun. All the while, nature around us transformed into what felt like a cool and breezy late summer evening. A few minutes later, everything was back to normal and the clouds covered it all once again like nothing had ever happened. The exact same cloud scenario happened both times—how lucky was that?

As for next Monday, I sincerely hope the clouds will stay home. I know so many folks who will travel from far and wide into the totality zone to experience this “Great American Eclipse.” It is actually fairly narrow, only about 100 miles wide, but stretches diagonally across the entire U.S.. For many, this will be a once in a lifetime opportunity to see such a rare event and I’m sure this experience will stay with them for years to come. It sure did for me.

I will actually not travel into the totality zone. Instead, I’ll be watching and talking about the partial eclipse that we can see up here in Massachusetts with my three year old son and his preschool class. A partial eclipse lasts for a couple of hours and occurs when the alignment between Earth, Moon, and Sun is just a bit “off.” Generally, this can happen when these three bodies are indeed not going to perfectly align. Or, when a person on Earth is close but not right in the totality zone, it causes a misalignment between the observer, the Moon, and the Sun. In both cases, the Sun is not going to get fully covered. Nevertheless, it is still a marvelous event and great for children and anyone interested to learn about solar eclipses and astronomy. And luckily enough, everyone in the U.S., Canada, and Mexico can watch a partial eclipse, no matter where you are located.

Solar eclipses don’t happen randomly. There are part of long lasting cycles that stem from the motion of the Moon around the Earth and the alignment of its orbit with respect to the Sun. This eclipse is part of the famous Saros cycle 145, and so was the 1999 eclipse I saw in Munich. It produces eclipses every 18 years, 11 days and 8h. Subsequent Saros eclipses are visible from different parts of the globe.The extra 8 hours in the cycle mean that from one eclipse to the next, the Earth must rotate an additional ~8 hours or ~120º. Hence, this eclipse is ~120º westward from continental Europe which is the continental U.S.. The next one will be visible from China in 2035. Each of the many Saros series typically lasts 12 to 13 centuries. Series 145 began in 1639 and will end in 3009 after 77 eclipses.

There are 4 to 6 total eclipses every year but not all are visible on land. Actually, from about any given point on Earth, once every 150 years an eclipse is visible. Now, it’s our turn. So if you’re not already traveling into the totality zone, make sure you still watch the partial eclipse—never without eclipse glasses, though, partial or total eclipse alike! Looking into the Sun causes serious longterm damage to your eyes but also your camera. So equip your camera with glasses, too! Alternatively, you can just watch the Sun’s shadow on a wall to observe how the Sun gets eaten away piece by piece by the incoming Moon. Ask your work if you can take a few minutes off. It’s a worthy cause. Actually, a well-timed bathroom break is almost long enough to catch totality or a glimpse of partial coverage. Eclipses are simply too rare and too beautiful to miss!

Get your eclipse glasses, rearrange your schedule (just a little bit), and make sure your kids or grandkids, friends and neighbors are seeing it too. Because, actually, the tides of the oceans on Earth are slowing down Earth’s rotation which make the Moon spiral outward and away from us by 1 inch per year. This means that the Moon will appear smaller and smaller with time, and in the far future, there won’t be any total eclipses possible anymore.

FrebelAnna Frebel is the Silverman (1968) Family Career Development Assistant Professor in the Department of Physics at the Massachusetts Institute of Technology. She has received numerous international honors and awards for her discoveries and analyses of the oldest stars. She is the author of Searching for the Oldest Stars: Ancient Relics from the Early Universe.