My Brief History — Chapter-by-Chapter Outline

Author: Stephen Hawking First published: 2013 Edition covered: First edition, Bantam Books, September 10, 2013 (144 pp., ISBN 978-0-345-53528-3). This is the only edition; no revised edition has been published. The book originated as an expansion of a lecture Hawking gave under the same title.

Central thesis

My Brief History is Stephen Hawking's first sustained autobiographical account, tracing the arc of his life from postwar childhood in Oxford and London through to his position as one of the most famous scientists in the world. The organizing claim of the memoir is that intellectual curiosity, sustained by structure and purpose, can flourish even — and perhaps especially — under conditions of extreme physical constraint. Hawking does not argue this sentimentally; he presents it as simple observation: his most productive decades of theoretical physics coincided with his progressive loss of muscular control.

The book is also a document of how the scientific ideas themselves evolved. Hawking uses each stage of his life as the occasion to explain the science he was doing at that time, so the memoir doubles as a compressed popular account of cosmology from the early 1960s to the 2010s — from the controversy over the Big Bang, through the thermodynamics of black holes, to the no-boundary proposal for the origin of the universe. The two threads — personal and scientific — are kept in parallel throughout.

How is it possible to understand the universe if one cannot fully control one's own body?

Chapter 1 — Childhood

Central question

What kind of family and early environment shaped the boy who would become a theoretical cosmologist?

Main argument

Frank Hawking and the family background

Stephen Hawking opens by tracing his father's family through Yorkshire tenant farmers. His great-grandfather John Hawking had been a prosperous farmer who went bankrupt during the agricultural depression at the turn of the twentieth century. Hawking's grandfather managed to send his own son Frank to Oxford, where Frank studied medicine and eventually became a researcher in tropical medicine. In 1937, Frank Hawking traveled to East Africa for fieldwork, and it was on one of his returns that he met and married Isobel, whose own family — Scottish in origin — had moved south.

Birth in Oxford during wartime

Stephen William Hawking was born on 8 January 1942 in Oxford. The choice of birthplace was deliberate: during the Second World War, the Germans and British had an informal agreement not to bomb Oxford and Cambridge, so Oxford was considered safer than London. The date — as Hawking notes with characteristic dryness — was exactly three hundred years after the death of Galileo.

Early childhood in Highgate

The family lived in Highgate, north London, in a house that Hawking recalls as large, somewhat dilapidated, and full of books. His parents' approach to reading and learning was unconventional: the school he attended in his earliest years did not formally teach reading, so Stephen did not read until he was eight. The household was intellectually alive but financially stretched; the family car was a converted London taxi. Stephen had three siblings: Mary, Philippa, and an adopted brother, Edward, who died in early adulthood.

The model train fascination and early interest in mechanism

From a young age, Hawking was fascinated by understanding how things worked. He was particularly captivated by model trains and spent hours constructing elaborate arrangements. He connects this childhood absorption with mechanical systems to the later drive that drew him toward theoretical physics — the desire to understand the underlying rules that govern observable behaviour, to see how the machine runs.

Key ideas

• The Hawking family's educational trajectory across three generations — from tenant farming to Oxford medicine — provides the specific social context for Stephen's own route to Cambridge.
• Wartime conditions directly determined where Hawking was born, an early instance of large historical forces shaping the most personal biographical facts.
• His early schooling was deliberately unstructured; formal reading instruction came late, yet the household was book-filled and conversation-rich.
• The model-train interest is offered not as mere anecdote but as the earliest form of what becomes a lifelong orientation: understanding systems from the inside.

Key takeaway

Hawking's childhood was shaped by a modest but intellectually ambitious household where curiosity about mechanisms — physical and conceptual — was the dominant inheritance.

Chapter 2 — St. Albans

Central question

How did Hawking's schooling and adolescent social world form the habits of mind that carried him to Oxford?

Main argument

The move and the new school

In 1950, Frank Hawking's work required a move to St. Albans, north of London, and the family took a large Victorian house that was in considerable disrepair. Stephen first attended the High School for Girls (which at the time also took boys up to a certain age), then passed the eleven-plus examination and entered St. Albans School. He describes the school as academically oriented and competitive; the question of university entrance — and specifically which university — was present from the beginning.

Choosing physics over medicine

Frank Hawking wanted his son to study medicine, the family profession. Stephen was uninterested; what gripped him was mathematics and physics, particularly the way they offered routes to understanding the deep structure of reality. This tension — parental expectation vs. authentic intellectual inclination — is one of the chapter's recurring themes, and Hawking presents it without drama as a simple divergence of interests that eventually resolved in his favour.

The friend group and the computing machine

Hawking describes a group of friends — several of whom later had scientific or mathematical careers — who built a rudimentary computer from old clock parts, telephone switchboard components, and recycled electrical parts. The project was partly playful and partly serious; it worked well enough to solve simple logical problems. Hawking notes the collaborative pleasure of building something conceptually elegant from cheap components as formative.

The unconventional family atmosphere

The Hawkings were, by the standards of a quiet cathedral town, conspicuously eccentric. They owned bees in the cellar and fireworks in the greenhouse, converted a Gypsy caravan for summer travel, drove the London taxi, and ate silently at mealtimes — each family member absorbed in a book. Stephen absorbed the message that intellectual absorption was more interesting than social conformity.

Key ideas

• The eleven-plus examination and the grammar school system positioned St. Albans School as a genuine academic route to Oxford, giving Hawking's choices a structural context they might not otherwise have had.
• The homemade computer project is the adolescent analog of the childhood model trains: a practical encounter with the pleasure of understanding how a system works.
• Parental ambitions for medicine versus Hawking's own gravitational pull toward physics is the first instance of him overriding external expectations in favour of what he actually wanted to understand.
• The family culture of reading and eccentricity is presented as having made intellectual seriousness feel normal rather than unusual.

Key takeaway

St. Albans gave Hawking a competitive academic environment, a peer group that shared his interest in building and thinking, and a family atmosphere that normalized intellectual intensity — the combination that prepared him for Oxford.

Chapter 3 — Oxford

Central question

What was Hawking's experience at Oxford, and how did his undergraduate years sharpen — or almost blunt — his intellectual ambition?

Main argument

Arrival and social difficulty

Hawking arrived at University College, Oxford, in October 1959 on a scholarship, intending to study natural sciences (with physics as the focus, since Oxford did not offer a straight physics degree at that time). He was seventeen — younger than most of his classmates, who had completed National Service — and he felt the age gap socially. The prevailing undergraduate culture at Oxford in that era actively discouraged the appearance of working hard; effort was considered unfashionable, and the ideal was effortless brilliance.

Coasting through — and its consequences

Hawking adapted to this culture, working very little. He estimates he spent perhaps a thousand hours of genuine work across three years — roughly an hour a day. He attended the minimum of lectures, relied on his ability to work problems out from first principles without extensive reading, and found that this was just enough to get by. He notes, without obvious regret, that this was a significant waste of time from the standpoint of learning physics: he arrived at Cambridge with large gaps in his knowledge that only became apparent when he started graduate work.

The Boat Club and social integration

The mechanism by which Hawking found his social footing was the Oxford University Boat Club. Unable to row because of his slight build, he became a coxswain — the person who steers the boat and calls the strokes — a role he performed with considerable skill and apparently with genuine pleasure. The Boat Club gave him a social network, a sense of belonging, and an identity within the university that his academic work alone had not.

The final examinations and a borderline result

Approaching his final examinations in 1962, Hawking was in genuine trouble: he had done so little systematic work that many areas of the syllabus were unfamiliar. He made a deliberate choice in the exam to answer only questions in theoretical physics — areas where he could reason from principles rather than rely on recalled detail — and to avoid experimental questions. The strategy worked narrowly, producing a result on the boundary between a first and second class degree. When examiners interviewed him to decide which class to award, he reportedly told them that if they gave him a first he would go to Cambridge, and if they gave him a second he would stay in Oxford. They gave him a first.

First symptoms and an Iranian earthquake

During his final Oxford year, Hawking noticed he was becoming clumsy — tripping, having difficulty tying his shoes. He did not investigate these symptoms immediately. After graduating, he traveled to the Middle East; during a stop in Iran he experienced an earthquake. He recalls the experience vividly as an early instance of confronting physical danger without the resources to respond quickly — a foreshadowing of the helplessness that would later define his physical existence.

Key ideas

• Oxford's culture of effortless performance actively discouraged the kind of systematic, hard work that would have served Hawking better in Cambridge; he absorbed the culture and later recognized it as a mistake.
• The coxswain role is an early example of finding an adapted contribution to a physical activity — participation through intelligence and coordination rather than strength.
• His examination strategy — restrict answers to theoretical questions, avoid areas requiring memorized detail — previews the way he would later do physics: pure theoretical reasoning, minimal dependence on experimental detail.
• The first neurological symptoms appear during his Oxford years but are not yet diagnosed; their presence in this chapter sets up the Cambridge chapter without yet naming the illness.

Key takeaway

Oxford gave Hawking confidence in theoretical reasoning but not in disciplined work; he arrived at Cambridge brilliant, somewhat lazily formed, and beginning to show the first physical symptoms he had not yet understood.

Chapter 4 — Cambridge

Central question

How did a terminal diagnosis become the paradoxical engine of Hawking's most important early scientific work?

Main argument

Arriving at Cambridge and Dennis Sciama

Hawking arrived in October 1962 intending to work with Fred Hoyle, the leading proponent of the steady-state theory of the universe. He was assigned instead to Dennis Sciama, a less famous but more personally available supervisor who proved to be an ideal mentor — broadly read, enthusiastic, and genuinely accessible for long theoretical conversations. Hawking initially regretted not being assigned to Hoyle but later recognized that Sciama's openness to conversation and his wide-ranging engagement with cosmology and particle physics served him better than Hoyle's more detached style would have.

The ALS diagnosis

Shortly after arriving at Cambridge, Hawking began falling more frequently and experienced increasing clumsiness. In the winter of 1962–63, during a visit home, his father arranged for him to see a specialist. After a series of tests — including a muscle biopsy and a lumbar puncture — he was diagnosed with amyotrophic lateral sclerosis (motor neurone disease). The doctors told him the disease would progress and that he had approximately two years to live.

Hawking describes his initial reaction as bleak. He had no purpose, felt that the physics he had wanted to do was now pointless, and began drinking heavily. He then describes a slow turn: a dream in which he was executed, which made him realize he still valued his life; a ward-mate dying of a blood disorder, which made his own situation seem relatively less hopeless; and, most significantly, falling in love with Jane Wilde, whom he had met at a New Year's party.

Jane Wilde and the decision to continue

Meeting Jane Wilde gave Hawking what he describes as a reason to live and a reason to complete his doctorate. If he was going to get married, he needed to show that he could support a family, which meant finishing a PhD and getting a position. This practical motivation aligned with a genuine intellectual reawakening: he began to work seriously for the first time. He and Jane became engaged in 1964 and married in July 1965.

Early cosmological work: singularities and the beginning of the universe

In his doctoral research, Hawking was drawn to the question of whether the universe had a true beginning — a point before which the concepts of space and time did not apply. This was not merely a cosmological question but a mathematical one: under what conditions do solutions to Einstein's field equations become singular (undefined, infinitely curved)?

Roger Penrose had recently proved a theorem showing that a collapsing star, under very general conditions, would produce a singularity at its centre — a point where the laws of physics as then understood broke down. Hawking realized that if you ran the Penrose argument backward in time, the expanding universe could be shown to have originated in a singularity: a Big Bang that was not just an extreme event but a genuine mathematical boundary of spacetime. This was a non-trivial result because it showed that the Big Bang singularity was not an artifact of special symmetry assumptions but a necessary consequence of general relativity under broad conditions.

The Adams Prize and the fellowship

Hawking's early work earned him a research fellowship at Gonville and Caius College. He and Penrose, together with Robert Geroch, developed a series of increasingly powerful singularity theorems. Their joint paper and the collaborative book The Large Scale Structure of Space-Time (with G.F.R. Ellis) became foundational texts in relativistic cosmology. The work earned Hawking and Penrose the Adams Prize in 1966.

Key ideas

• The ALS diagnosis, paradoxically, gave Hawking focus: for the first time he had a reason to work hard rather than coast.
• Dennis Sciama's mentorship was formative — his accessibility and intellectual range exposed Hawking to the full landscape of 1960s cosmology and particle physics at a crucial moment.
• The singularity theorems established Hawking's early reputation; they showed that the Big Bang and black hole singularities were not special-case curiosities but generic predictions of general relativity.
• Jane Wilde's role is described explicitly and without embarrassment: she was the practical motivation to complete the work at the moment when motivation was most at risk.

Key takeaway

At Cambridge, a terminal diagnosis — combined with falling in love — produced in Hawking the determination to work seriously for the first time, and the scientific environment produced some of the most consequential early results in relativistic cosmology.

Chapter 5 — Gravitational Waves

Central question

Why did Hawking, at the boundary between experimental and theoretical physics, ultimately choose pure theory?

Main argument

Weber's claims and the question of detection

In 1969, the American physicist Joseph Weber announced that he had detected gravitational waves using large aluminium bars suspended in vacuum chambers. The detectors — later called Weber bars — were designed to resonate if a gravitational wave passed through them, stretching and compressing space at the detector's location. Weber claimed to be detecting wave bursts at a rate that implied very frequent, very energetic astrophysical events — rates that many theorists found implausible.

Hawking visited Weber's laboratory at the University of Maryland in 1970. He found the experimental setup careful and the experimenters competent, but the claimed event rates struck him as inconsistent with what was known about the density of potentially wave-emitting objects in the local universe. Independent attempts to replicate Weber's results failed; the physics community eventually concluded that Weber had been detecting noise artifacts rather than gravitational waves.

The Hawking–Gibbons detector proposal — and its withdrawal

Stimulated by the debates around Weber's work, Hawking and his student Gary Gibbons drafted a proposal for a new type of gravitational wave detector. They submitted a funding application to the Science Research Council. But as Hawking describes it, he reflected seriously on whether experimental work was genuinely practical given his advancing disability. The hands-on demands of maintaining experimental apparatus — the alignment, the calibration, the late-night interventions when something went wrong — were already beyond him. He and Gibbons withdrew the application.

Choosing theory

The episode clarified something for Hawking that had perhaps been implicit since Oxford: theoretical physics, in which the work consists of thought, paper, and conversation, was not merely his preference but, increasingly, the only mode available to him. He observes that this constraint was not as limiting as it might seem — theoretical physicists have contributed foundationally to science without needing to run a single experiment. The observation is made without self-pity; it reads as a practical recognition.

The eventual vindication of gravitational wave detection

The chapter allows Hawking to note briefly that the question Weber had been trying to answer — whether gravitational waves could be directly detected — was eventually answered affirmatively. The LIGO detectors, vastly more sensitive than anything Weber built, detected gravitational waves from merging black holes in 2015, confirming a prediction of general relativity first made a century earlier.

Key ideas

• Weber's claims were significant enough to prompt several independent groups to attempt replication; the failure to replicate was the community's correction mechanism working as it should.
• The withdrawn detector proposal is a rare instance of Hawking explicitly mapping his disability onto a professional decision in real time, rather than retrospectively.
• Gravitational wave detection ultimately succeeded — Hawking includes this as background context — but by a different technology and a different generation.
• The episode reinforces the memoir's wider argument: that constraints on what you cannot do can clarify what you can, and that working within those constraints is not defeat.

Key takeaway

The gravitational waves episode produced, as a by-product, Hawking's definitive commitment to theoretical rather than experimental physics — a choice that his disability had already made for him, and that proved entirely consistent with the highest level of scientific contribution.

Chapter 6 — The Big Bang

Central question

How did the scientific community's resistance to a universe with a beginning shape the debate that Hawking's doctoral work entered — and helped resolve?

Main argument

The cosmological debate of the 1960s

By the early 1960s, cosmology was divided between two competing models of the universe. The steady-state theory, developed principally by Fred Hoyle, Thomas Gold, and Hermann Bondi, held that the universe had no beginning and no end: it had always existed, and as it expanded, new matter was continuously created to maintain a constant average density. The Big Bang theory held that the universe began from an extremely hot, dense initial state and had been expanding ever since. Many physicists, including Hoyle (who coined the term "Big Bang" as a dismissive label), found the idea of a universe with a beginning philosophically uncomfortable — it seemed too close to a creation event.

The microwave background changes the game

In 1965, Arno Penzias and Robert Wilson at Bell Laboratories detected a faint microwave signal coming uniformly from all directions in the sky. This was the cosmic microwave background radiation — the heat signature of the hot early universe, now cooled to about 2.7 degrees above absolute zero as the universe expanded. Its existence had been predicted by Big Bang theory; the steady-state theory had no natural explanation for it. After this discovery, the steady-state theory was effectively abandoned by most cosmologists.

Hawking's doctoral question: did the universe necessarily begin in a singularity?

Hawking's specific contribution was mathematical. Even if the universe expanded from a hot dense state, it was not immediately obvious whether that initial state was a true singularity — a point where the curvature of spacetime became infinite and the laws of physics broke down — or whether it might have been a very extreme but finite state that physics could still describe. Special symmetrical models produced singularities, but special symmetry is not realistic.

Penrose's singularity theorem for collapsing stars provided the key tool. Hawking recognized that the same mathematical argument could be run in reverse, for an expanding rather than a contracting universe. Applying it, he showed that under the very general conditions described by general relativity — without needing to assume special symmetry — an expanding universe with the properties we observe necessarily had a singular beginning.

The Penrose–Hawking singularity theorems

Working independently and then collaboratively with Roger Penrose and Robert Geroch, Hawking developed a series of singularity theorems of increasing generality. The culminating result, published with Penrose in 1970, showed that a very general class of spacetimes — those satisfying reasonable physical energy conditions and lacking closed timelike curves — must contain singularities. The theorems applied both to the Big Bang and to black holes, unifying the two phenomena under the same mathematical framework.

The theorems were recognized immediately as a major advance. Their significance was not merely cosmological but foundational: they showed that general relativity, taken seriously, predicted its own breakdown at singularities, which meant that a quantum theory of gravity would eventually be required to describe those regimes.

Key ideas

• The steady-state vs. Big Bang debate was not just scientific but ideological; many physicists resisted a creation event on philosophical grounds, and the microwave background settled the empirical question against them.
• The singularity theorems required no special symmetry assumptions; their generality was precisely what made them significant.
• The theorems show that general relativity predicts the limits of its own applicability — the singularities are not a failure of the theory but a built-in signal that a deeper theory is needed.
• Hawking and Penrose's collaboration produced results neither could have reached alone; Penrose supplied the topological tools, Hawking the cosmological application.

Key takeaway

The singularity theorems established that the universe necessarily began in a Big Bang singularity — not as a feature of special initial conditions but as a general consequence of general relativity, pointing toward the need for a quantum theory of the very early universe.

Chapter 7 — Black Holes

Central question

How did the study of black holes lead Hawking to his most famous discovery — that black holes are not entirely black?

Main argument

Historical background: from dark stars to event horizons

Hawking sketches the history of the concept. In 1783, the English clergyman John Michell imagined a "dark star" — a body so massive that light could not escape its gravitational pull. Laplace made a similar calculation in 1796. The modern formulation came from Einstein's general relativity: Karl Schwarzschild found, in 1916, the exact solution describing the spacetime geometry around a spherically symmetric mass. Robert Oppenheimer and his student Hartland Snyder showed in 1939 that sufficiently massive stars, exhausting their nuclear fuel, would undergo gravitational collapse and form a region from which nothing — not even light — could escape. Einstein himself doubted such objects could exist.

The renaissance of black hole physics in the 1960s

The discovery of quasars in the early 1960s revived interest in black holes. Quasars — enormously luminous objects at cosmological distances — required energy outputs explainable only by massive gravitational collapse. John Wheeler, who popularized the term "black hole" in 1967, Roger Penrose, and others began developing the formal theory of these objects. The event horizon — the boundary beyond which escape is impossible — became the central concept.

Hawking's area theorem

In 1970, working with the causal structure tools he had developed for the singularity theorems, Hawking proved that the area of a black hole's event horizon can never decrease: in any physical process involving black holes, the total horizon area either stays constant or increases. This result — the area theorem — had an immediate and puzzling consequence: it was formally analogous to the second law of thermodynamics, which states that entropy (disorder) in a closed system never decreases. The formal resemblance suggested that a black hole's horizon area was somehow connected to its entropy.

The no-hair theorem

Hawking, together with Brandon Carter and David Robinson, worked on the no-hair theorem: the result that a stationary black hole (one not changing with time) is completely characterized by just three parameters — its mass, its electric charge, and its angular momentum (spin). All other information about what fell in to form the black hole is inaccessible from outside. Two black holes with identical mass, charge, and spin are physically indistinguishable regardless of what they were made of.

Hawking radiation: quantum effects at the event horizon

The most surprising result came in 1974. Applying quantum field theory in the curved spacetime of a black hole — a calculation that required combining general relativity with quantum mechanics in a regime where neither was obviously primary — Hawking discovered that black holes should emit a faint thermal radiation. The mechanism involves the quantum vacuum: near the event horizon, pairs of virtual particles are continuously created and annihilated. Occasionally, one member of a pair falls into the black hole while the other escapes. From outside, the escaping particle appears as radiation with a thermal spectrum — the temperature being inversely proportional to the black hole's mass.

This Hawking radiation implied that black holes are not truly black: they slowly emit energy and, if nothing falls in to compensate, they slowly evaporate. A small black hole has a higher temperature and evaporates faster; a stellar-mass black hole would take enormously longer than the current age of the universe to evaporate appreciably. But the result was theoretically fundamental: it connected gravity, quantum mechanics, and thermodynamics in a single calculation.

The information paradox

Hawking radiation introduced what became one of the most debated questions in theoretical physics: the black hole information paradox. If a black hole forms from matter in a definite quantum state and then evaporates by emitting thermal radiation (which carries no information about the original state), where does the information go? Quantum mechanics requires that information is not destroyed; thermal radiation carries no specific information about what created it. Hawking initially argued that information was genuinely lost — a deeply controversial position. He describes the paradox as analogous to burning an encyclopedia: even though the material is not destroyed, the information encoded in it is practically irretrievable.

Key ideas

• The area theorem (1970) was the first result suggesting a deep connection between black hole geometry and thermodynamics — later made precise by Bekenstein's entropy proposal and Hawking's radiation.
• The no-hair theorem shows that black holes are radically simple objects: three numbers specify them completely, and all complexity of their formation is hidden.
• Hawking radiation (1974) was greeted with initial scepticism by Hawking's own supervisor, Dennis Sciama, and by John Wheeler — both later accepted it as correct.
• The information paradox remains open; Hawking himself changed his position in 2004, conceding that information is probably not lost, but the full resolution is still debated.
• The result that black holes emit thermal radiation unified thermodynamics, general relativity, and quantum mechanics in a single formula, making it one of the most celebrated results in modern theoretical physics.

Key takeaway

Hawking's work on black holes moved from classical geometry (the area theorem, the no-hair theorem) to the discovery that quantum effects make black holes radiate — a result that connected gravity, quantum theory, and thermodynamics and introduced the unsolved information paradox that still drives fundamental physics research.

Chapter 8 — Caltech

Central question

How did Hawking's repeated visits to the California Institute of Technology shape his collaborations and his scientific bets?

Main argument

The Sherman Fairchild Visiting Professorship

In 1974, Hawking was offered a Sherman Fairchild Distinguished Visiting Professorship at Caltech. He spent the 1974–75 academic year there, the first of what became a long-running association: from the early 1990s onward, he visited Caltech for several weeks nearly every year. The institution — with its concentration of relativists, astrophysicists, and quantum physicists — was one of the few places in the world where Hawking could have sustained conversations with people thinking about the same class of problems at the same level of depth.

Kip Thorne and the Cygnus X-1 wager

At Caltech, Hawking's primary collaborator and intellectual sparring partner was Kip Thorne, the leading American expert on general relativity and gravitational waves. Their most famous exchange was a bet placed in 1975 (formalized in a written contract): Hawking wagered that Cygnus X-1 — a binary X-ray source in which one component appeared to be far too massive to be anything other than a black hole — was in fact not a black hole. He described the bet explicitly as an insurance policy: if black holes did not exist, he would at least win a subscription to the satirical magazine Private Eye to compensate for losing the theoretical work that depended on their existence. In 1990, Hawking conceded the bet. Cygnus X-1 is now regarded as one of the clearest examples of a stellar-mass black hole.

The atmosphere at Caltech: Feynman and others

Hawking describes the intellectual culture at Caltech as unusually direct and unintimidating — a place where one was expected to challenge ideas rather than defer to seniority. He recalls interactions with Richard Feynman as emblematic of this atmosphere: Feynman was dismissive of formality and had no patience for vague answers, but he engaged seriously with problems he found interesting. The contrast with the more hierarchical Cambridge atmosphere is drawn gently.

Scientific productivity and the California environment

Hawking found California both socially enjoyable and scientifically productive. The combination of a concentrated community of relativists, the regular contact with experimentalists working on gravitational physics, and the lighter administrative load during visiting appointments made Caltech periods among his most productive. He notes the practical role played by his students and postdoctoral researchers, who became indispensable as his physical disability advanced — they handled blackboard work, literature searches, and increasingly served as his hands in collaborative calculations.

Key ideas

• The Cygnus X-1 bet was not a scientific result but a device for dramatizing the stakes of theoretical work: Hawking's bet against black holes existing was protection against being wrong about the most consequential ideas of his career.
• Conceding the bet in 1990 was a gesture of scientific honesty made publicly and without embarrassment; it also confirmed that the area of physics he had spent his career developing was built on real phenomena.
• Caltech's culture, shaped by figures like Feynman and Thorne, complemented and contrasted with Cambridge in ways that Hawking found intellectually stimulating over decades of visits.
• The role of students and postdocs as physical proxies for Hawking's increasingly limited motor function is described here as a practical collaborative model that sustained his productivity.

Key takeaway

Caltech gave Hawking a second scientific home where direct intellectual engagement and a concentration of talent in relativistic physics enabled both sustained collaboration and the famous wagers that dramatized his scientific commitments.

Chapter 9 — Marriage

Central question

How did the demands of Hawking's disability reshape his marriage to Jane Wilde, and how did both marriages eventually end?

Main argument

Jane Wilde and the early years

Jane Wilde and Hawking married in July 1965, a few months after his diagnosis had been confirmed and his two-year prognosis communicated. Jane has described the marriage as a deliberate choice to provide support and to give Hawking the stability and domestic structure he needed to work. Hawking acknowledges this explicitly. The early years were demanding: he was on crutches and then a wheelchair, they had three children in relatively quick succession (Robert in 1967, Lucy in 1970, and Timothy in 1979), and the combination of three young children with round-the-clock care needs for a progressively disabled husband fell primarily on Jane.

The practical arrangements and their strains

As Hawking's condition advanced through the 1970s, the household required increasing outside help. Graduate students and postdoctoral researchers took on roles that went beyond academic assistance, helping with physical care and daily logistics. The physical demands were considerable; the emotional and relational consequences were significant. Hawking notes, with some restraint, that the strains on the marriage were real, and that the arrangement that Jane made — bringing choirmaster Jonathan Hellyer Jones into the household as a friend and helper after Timothy's birth in 1979 — changed the family's internal dynamic. He acknowledges that Jane's relationship with Hellyer Jones eventually became a central one in her life, and that his own response to this was one of frustration.

The tracheotomy, communication, and Elaine Mason

In 1985, while revising the manuscript of A Brief History of Time in Geneva, Hawking contracted pneumonia and had to be connected to a life-support machine. Jane was confronted with the choice of whether to authorize a tracheotomy that would save his life but eliminate the remnants of his natural voice. She authorized it. The operation was successful but left Hawking entirely without speech; the subsequent arrival of the speech synthesis software provided by Walt Woltosz (the Equalizer program, later adapted for Hawking's use) and the hardware provided by David Mason gave him a new voice — one that became globally recognizable.

David Mason's wife, Elaine Mason, was a nurse. She became one of the nurses working the overnight shifts in the Hawking household. By 1990, Hawking's relationship with Elaine Mason had become central to his life; he left the family home and moved with her. He and Jane divorced in 1995. That same year, he married Elaine Mason.

The second marriage and its end

The second marriage was, by public accounts, difficult; Hawking's children expressed concern about their access to their father and about his welfare. The marriage ended in divorce in 2006. Hawking notes this briefly. After the second divorce, he resumed close relationships with Jane, his children, and eventually his grandchildren.

Key ideas

• Jane Wilde's decision to marry Hawking when his prognosis was two years is presented as an act of deliberate will rather than naivety; she knew the diagnosis.
• The progressive outsourcing of physical care to graduate students and nurses created a household structure that was intellectually productive and personally complex.
• The 1985 tracheotomy is a hinge event: it ended Hawking's natural voice but the speech synthesizer that replaced it gave him a recognizable and persistent mode of communication.
• The memoir is notably restrained about the personal details of both marriages; it reports events without extended emotional analysis.

Key takeaway

Hawking's marriages were shaped by the extraordinary demands of his disability — the first sustained by Jane's determined support and eventually strained beyond recovery; the second brief and troubled; the later reconciliation with his first family quiet and unremarked.

Chapter 10 — A Brief History of Time

Central question

How did A Brief History of Time come to be written, and what does its improbable success reveal about the relationship between science and popular culture?

Main argument

The financial motivation

By the early 1980s, Hawking's care costs had become substantial. Round-the-clock nursing, adapted equipment, and the general expenses of supporting a family on an academic salary required supplementary income. He decided to write a popular book about cosmology aimed at the general public. He had given popular lectures; the project was an extension of that practice rather than a departure from it.

Simon Mitton and the early negotiations

He first approached Simon Mitton, the editor in charge of astronomy books at Cambridge University Press, who had worked with Hawking on his academic books. Mitton was interested but told Hawking the draft he had seen was too technical for a trade readership; the conventional wisdom about popular science was that each equation halved the sales. Cambridge University Press offered £10,000 — at that point their largest advance.

Al Zuckerman, the auction, and Bantam

Literary agent Al Zuckerman had learned of the project and approached Hawking before the Cambridge University Press contract was signed. Zuckerman organized an auction between major publishers. Bantam Books, through a bid of $250,000 — twenty-five times the Cambridge offer — won the auction. Bantam's editor Peter Guzzardi became the crucial creative partner; Guzzardi sent back repeated detailed editorial notes requesting clearer explanations of each technical concept. The back-and-forth was extensive; Hawking found it demanding but ultimately productive.

The 1985 pneumonia crisis and the voice

The manuscript was nearly complete when Hawking contracted pneumonia in Geneva in August 1985. After the tracheotomy that saved his life (described in Chapter 9), Hawking's first messages via his new speech-generating device included a request for assistance finishing the book. The technical apparatus of his new communication — speaking by selecting words on a screen, then producing synthesized speech — slowed his writing to approximately a word per minute but also, paradoxically, encouraged more careful selection of words.

Publication, reception, and cultural phenomenon

A Brief History of Time was published in the United States in April 1988. The initial print run was modest; Bantam expected respectable but not extraordinary sales. Instead, the book immediately sold out and remained at the top of bestseller lists for months, eventually appearing on the Sunday Times list for 237 consecutive weeks — a record. It has sold approximately nine million copies and been translated into forty languages.

The reasons for the extraordinary success were debated at the time and since. Hawking notes with dry humour that many people bought the book without necessarily reading it — John Maddox, editor of Nature, surveyed Californian readers and found that the book was widely known but less widely read. The cultural theorist's answer is that the book filled a specific role: it provided a route into the largest questions — origin of the universe, nature of time, existence of God — through the authority of physics, and it did so without equations.

Hawking's mother, Isobel, defended the book against critics who said its language was still too difficult: the ideas themselves were difficult, she argued, not the language; and the difficulty was the point.

Key ideas

• The book was motivated by financial necessity, not by a considered publishing strategy; the scale of its success was unexpected by everyone, including Hawking.
• Peter Guzzardi's editing was central: the repeated requests for clarification pushed Hawking toward a level of explanatory precision that no academic audience would have demanded.
• The cultural phenomenon of a physics book on every coffee table raised questions about reading, scientific authority, and intellectual aspiration that are still not fully resolved.
• The book's success enabled Hawking to fund his care and secured his public position as the globally recognized symbol of physics, which in turn shaped everything that came after — including, eventually, the memoir in which he is now describing it.

Key takeaway

A Brief History of Time was written out of financial necessity, shaped by the editorial demands of a mass-market publisher, and became one of the best-known books of the twentieth century — a publishing event that altered Hawking's life and that he regards with qualified, sceptical satisfaction.

Chapter 11 — Time Travel

Central question

Is travel to the past possible, and what does physics say about the conditions under which it might or might not be?

Main argument

The theoretical background: closed timelike curves

Hawking frames the chapter around a specific mathematical concept: closed timelike curves (CTCs) — paths through spacetime that loop back on themselves and return to the same point in both space and time. General relativity does not prohibit such curves in principle; certain exact solutions to Einstein's equations (such as the rotating universe solution found by Kurt Gödel in 1949) contain them. If CTCs exist, an observer following one would return to their own past.

Wormholes and the Kip Thorne proposal

Stimulated by a question from Carl Sagan who needed a scientifically plausible mechanism for interstellar travel for his novel Contact, Kip Thorne and his students Michael Morris and Ulvi Yurtsever (at Caltech) explored in 1988 whether traversable wormholes — shortcuts through spacetime connecting distant points — were permitted by general relativity. They found that such wormholes were in principle possible but required exotic matter with negative energy density to hold them open. Moreover, a traversable wormhole, if one could be created and then accelerated at different rates at each mouth, could in principle function as a time machine.

The chronology protection conjecture

Hawking's response was sceptical. In 1992, he proposed the chronology protection conjecture: that the laws of physics conspire to prevent the formation of closed timelike curves on macroscopic scales, thereby protecting the consistency of the universe's causal structure. The proposed mechanism is quantum mechanical: near a potential Cauchy horizon (the boundary at which closed timelike curves would first form), quantum vacuum fluctuations build up in an exponentially growing cascade. The resulting energy-momentum tensor diverges before the CTC can form, destroying the wormhole or the time machine before it becomes operational.

Hawking notes that this remains a conjecture rather than a theorem — the calculation requires a full theory of quantum gravity in the relevant regime, which does not yet exist. But he regards the empirical evidence as strongly suggestive: we have not been visited by tourists from the future.

The 2009 party for time travelers

To test his conjecture in the most direct possible way, Hawking held a champagne reception in 2009 specifically for time travelers. The reception was publicized only after it had taken place, so only someone from the future who had received the invitation could have attended. No one appeared. Hawking presents this with characteristic dry humour as empirical support for the chronology protection conjecture, while acknowledging its obvious limitations as a scientific test.

Key ideas

• Closed timelike curves are not obviously forbidden by general relativity; the question is whether quantum effects forbid them in practice.
• The wormhole proposal by Thorne et al. was a serious piece of general relativistic physics, not science fiction; its requirement for exotic matter with negative energy density is the practical obstacle.
• The chronology protection conjecture is motivated by the desire to preserve logical consistency (avoid grandfather paradoxes) and by the quantum mechanical calculation showing that CTCs cannot form without a quantum instability.
• The empirical argument from the absence of time tourists is offered as humour but also as a genuine (if informal) evidentiary point.

Key takeaway

Hawking regards time travel to the past as effectively impossible — not because general relativity forbids it but because quantum effects appear to prevent the formation of the timelike curves it would require — and he proposed the chronology protection conjecture to articulate this as a physical law.

Chapter 12 — Imaginary Time

Central question

What is imaginary time, and what role does it play in Hawking's approach to quantum cosmology?

Main argument

The technical background: Euclidean quantum gravity

Hawking explains the concept of imaginary time — a mathematical device central to his approach to quantum gravity. In ordinary physics, time is described by real numbers. If one replaces real time t with imaginary time τ = it (where i is the square root of −1), the metric signature of spacetime changes from Lorentzian (three spatial dimensions and one time dimension with opposite sign) to Euclidean (four spatial dimensions, all with the same sign). In this Euclidean formulation, there are no singularities and no initial or final boundaries — spacetime becomes a smooth, compact four-dimensional space.

The practical use of this device was known from quantum field theory: integrals over imaginary time ("Wick rotation") often converge when the corresponding real-time integrals do not. Hawking adopted the Euclidean path integral approach to quantum gravity as a way of calculating quantum-gravitational effects without running into the singularities that plague the real-time description.

Connection to the path integral approach

Richard Feynman's sum-over-histories (path integral) approach to quantum mechanics says that the probability of going from one state to another is calculated by summing over all possible histories connecting those states, each weighted by a phase factor. Hawking and Jim Hartle applied this to the universe itself: the "wave function of the universe" is calculated by summing over all compact four-dimensional Euclidean geometries. In imaginary time, these are smooth four-dimensional spaces — there is no special boundary, no initial singularity, no moment of creation.

Imaginary time and the origin of the universe

The key consequence — developed fully in the no-boundary proposal (Chapter 13) — is that asking "what happened before the Big Bang?" may be as meaningless as asking "what is south of the South Pole?". In imaginary time, the universe is a closed, finite four-dimensional space with no boundary. The question of an origin does not arise: every point in imaginary time is as much an interior point as any other. The Big Bang singularity of real time is replaced, in imaginary time, by a smooth region analogous to the North Pole — a genuine point in the space but not a boundary of it.

What imaginary time "means"

Hawking is careful about the physical interpretation. Imaginary time is a mathematical tool whose relationship to "real" physical time is not fully understood. One position is that imaginary time is merely a computational device: it makes integrals tractable and calculations better-defined, but physical observables must ultimately be expressed in real time. Another position — which Hawking is drawn to — is that imaginary time is as real as ordinary time, and that the distinction between the two is a feature of how we happen to describe things rather than a fundamental feature of the world. He does not insist on the stronger interpretation but presents both.

Key ideas

• Imaginary time is a well-defined mathematical operation (Wick rotation) with established uses in quantum field theory; Hawking's application to cosmology extends a known technique into a new domain.
• In imaginary time, spacetime becomes a smooth Euclidean manifold with no singularities; the Big Bang is not a boundary but a smooth interior point.
• The sum-over-histories interpretation gives the no-boundary proposal a clear formal meaning: the wave function of the universe is a sum over all compact four-geometries without boundary.
• The interpretive question — whether imaginary time is "real" — is left open; the scientific content of the proposal does not depend on resolving it.

Key takeaway

Imaginary time is Hawking's technical device for doing quantum cosmology without singularities; in imaginary time, the universe has no edge and no beginning in the sense of a boundary, which sets up the no-boundary proposal for the origin of everything.

Chapter 13 — No Boundaries

Central question

If the universe has no boundary in imaginary time, what follows for the questions of creation, divine causation, and the ultimate theory of physics?

Main argument

The Hartle–Hawking state

In 1983, Hawking and James Hartle published what became known as the Hartle–Hawking no-boundary proposal (or the Hartle–Hawking state). The proposal applies the Euclidean path integral approach to the wave function of the entire universe. The key claim: the wave function of the universe is given by a sum over all compact, smooth four-dimensional Euclidean geometries — geometries with no boundary. In this framework, the universe does not have a beginning in imaginary time; it simply exists as a finite four-dimensional space without an edge.

When this wave function is translated back into real time, it describes a universe that spontaneously began expanding — but the "beginning" is not a singularity or a boundary; it is the analogue of the North Pole. There is no moment at which the universe was created, and therefore no causal prior state — no "before" — about which one needs to ask.

Implications for the concept of creation

The no-boundary proposal has a direct bearing on the question of whether the universe requires a creator or a prior cause. If the universe has no boundary in imaginary time and no initial singularity, then there is no moment at which something external needed to set it going. Hawking addresses this directly: the proposal eliminates the role of a creator not by argument but by making the relevant question — what caused the Big Bang? — mathematically ill-formed. There is no "before" because there is no boundary.

He is careful not to overstate this: the no-boundary proposal is a conjecture, not a proven theory. And the question of why the laws of physics take the form they do — why there is a wave function at all — remains open. The proposal removes one form of the creation question without claiming to remove all forms.

Top-down cosmology

A later development Hawking describes is top-down cosmology, developed with Thomas Hertog. Classical cosmology asks: given the initial conditions of the universe, what do we observe today? Top-down cosmology reverses this: given what we observe today, what initial conditions are consistent with those observations? The approach is motivated by the observation that in the no-boundary proposal, there is no single classical history of the universe but a quantum superposition of histories; the question of which history we observe is partly determined by the kind of observers we are. The approach connects the no-boundary proposal to the broader questions of anthropic reasoning in cosmology.

The M-theory horizon

The chapter closes with Hawking's reflections on the state of fundamental physics at the time he was writing. String theory and its extension, M-theory, held out the promise of a unified framework encompassing general relativity and quantum mechanics, with a landscape of possible physical laws rather than a unique theory. Hawking regards this landscape not as a failure of physics but as a feature: the conditions in which observers like us can exist constrain which part of the landscape is relevant to our questions. The no-boundary proposal, in this context, is the beginning of a quantum cosmological account of why we find ourselves in a universe with the laws we observe.

Key ideas

• The no-boundary proposal gives a precise mathematical meaning to the idea that the universe had no beginning: in imaginary time, it is a smooth closed four-geometry with no edge.
• The theological implication is not argued but follows from the mathematics: no boundary means no prior cause, which removes one formulation of the creation question without addressing others.
• Top-down cosmology recasts the relationship between initial conditions and observations, making the observer's existence part of the calculation.
• M-theory's landscape of possible physical laws is not, for Hawking, a defeat for physics but a context in which the no-boundary proposal becomes even more relevant.
• The memoir ends with Hawking noting that it has been a glorious time to be alive and doing research in theoretical physics — a phrase that recurs in the Kirkus review as encapsulating the book's quiet satisfaction with a life well used.

Key takeaway

The no-boundary proposal — the book's final and largest scientific idea — holds that the universe is self-contained in imaginary time, without a boundary, without a prior cause, and without a beginning in the conventional sense; and Hawking presents this not as speculation but as the best current answer physics can give to the oldest question: why is there something rather than nothing?

The book's overall argument

1. Chapter 1 (Childhood) — Establishes the family and cultural conditions that made a theoretical physicist possible: intellectual curiosity, modest means, and a household where ideas mattered more than convention.
2. Chapter 2 (St. Albans) — Shows how a competitive grammar school environment and a peer group interested in building and thinking gave Hawking's curiosity its first directed form, and how he chose physics over medicine against his father's wishes.
3. Chapter 3 (Oxford) — Documents the risks of intellectual coasting — a culture that penalized effort and rewarded effortless display — and the narrow escape of a first-class degree, alongside the first, still-unnamed symptoms of the disease that would redefine his life.
4. Chapter 4 (Cambridge) — Presents the paradox at the memoir's heart: a terminal diagnosis, given at the moment of greatest vulnerability, became the engine of focused work; the singularity theorems established Hawking as a first-rank theorist, and Jane Wilde gave him the reason to keep going.
5. Chapter 5 (Gravitational Waves) — Marks Hawking's definitive turn to pure theory: the episode of Weber's claims and the withdrawn detector proposal clarified, against his disability, what kind of physicist he could and would be.
6. Chapter 6 (The Big Bang) — Explains the cosmological context — the defeat of the steady-state theory, the significance of the microwave background — in which Hawking's singularity theorems were the decisive mathematical contribution.
7. Chapter 7 (Black Holes) — Traces the arc from classical geometry (area theorem, no-hair theorem) to the quantum-mechanical discovery of Hawking radiation, demonstrating how the encounter between general relativity and quantum mechanics produces the most surprising results and the deepest open problems.
8. Chapter 8 (Caltech) — Expands the scientific geography beyond Cambridge: Caltech provided sustained contact with Kip Thorne, a culture of direct intellectual engagement, and the occasion for the famous wagers that dramatized the stakes of black hole physics.
9. Chapter 9 (Marriage) — Places the personal cost of Hawking's scientific productivity in full view: the structure that enabled the physics — the nursing care, the household arrangements, Jane's sacrifices — was also the structure that eventually dissolved his first marriage.
10. Chapter 10 (A Brief History of Time) — Shows how financial necessity produced the most culturally consequential science book of its era, and how a trade editor's relentless demand for clarity forced a higher standard of popular explanation than any academic audience would have required.
11. Chapter 11 (Time Travel) — Applies the tools of general relativity and quantum mechanics to the question of temporal causality, arriving at the chronology protection conjecture: the laws of physics appear designed to prevent time travel, protecting the causal structure of the universe.
12. Chapter 12 (Imaginary Time) — Introduces the mathematical device — replacing real time with imaginary time to produce a smooth Euclidean spacetime — that makes the no-boundary proposal technically tractable, removing singularities and boundaries from the description of the universe.
13. Chapter 13 (No Boundaries) — Delivers the culminating scientific and philosophical claim: that in imaginary time, the universe has no boundary, no beginning, and no prior cause; that the question "what happened before the Big Bang?" is as ill-formed as "what is south of the South Pole?"; and that this constitutes the best current answer physics can provide to the question of why the universe exists.

Common misunderstandings

Misunderstanding: This is primarily a disability memoir about overcoming adversity.

The book does not present Hawking's life as an inspirational narrative about defeating illness. The ALS diagnosis is treated as a practical and scientific fact that shaped his working methods and his priorities, not as the memoir's emotional centre. Hawking explicitly resists the framing of disabled genius as inspiring spectacle — he notes, with some impatience, that his celebrity is partly an artifact of that framing.

Misunderstanding: Hawking radiation has been observed and confirmed experimentally.

The memoir makes clear that Hawking radiation is a theoretical prediction from a calculation combining general relativity and quantum mechanics. For black holes of astrophysical mass, the radiation is far too faint to detect with any existing or planned instrument. The prediction is accepted by the physics community on theoretical grounds, not because it has been measured.

Misunderstanding: The no-boundary proposal proves there is no God.

Hawking is careful in the memoir not to make this claim. The no-boundary proposal eliminates the need for a creator only in the specific sense that it removes the initial singularity — the moment at which something external would have had to set the universe going. It does not address the question of why the laws of physics exist, or why the no-boundary proposal itself should describe nature. The theological implications are real but narrow.

Misunderstanding: A Brief History of Time is about Hawking's life.

The title A Brief History of Time (1988) is frequently confused with My Brief History (2013). They are different books. The former is a popular cosmology book with no autobiographical content; the latter is the memoir covering his personal history and scientific development. The confusion is understandable given the similarity of the titles — and Hawking plays on this similarity deliberately.

Misunderstanding: The Caltech and gravitational wave chapters are scientific digressions from an otherwise personal memoir.

The book is structured so that each chapter covers a period of Hawking's life while simultaneously explaining the science he was working on during that period. The scientific chapters are not digressions but the primary content; the personal narrative is the connective tissue. The book is a memoir of a scientific mind, not a biography of a person who happened to do science.

Central paradox / key insight

The central paradox of My Brief History is that Hawking's most productive period — the decades that produced the singularity theorems, the area theorem, Hawking radiation, and the no-boundary proposal — were also the decades during which his physical capabilities declined most steeply. He went from walking with difficulty, to using crutches, to a wheelchair, to complete loss of speech, to communication at one word per minute through a computer interface — and during this arc he produced the work for which he is primarily remembered.

The book does not resolve this paradox so much as sit with it. Hawking's own explanation is practical: his disability forced him toward a mode of physics — pure theoretical reasoning, minimal experimental participation, maximum reliance on geometric and topological intuition — that happened to be exactly the mode most productive for the problems he was working on. A physics that could be done entirely in the head, on paper, and in conversation was available to him in a way that experimental or computational physics was not. The constraints concentrated rather than diminished him.

"When one's expectations are reduced to zero, one really appreciates everything one does have."

The insight that emerges is not about disability per se but about how constraints shape the form that productive work takes. The same principle appears in the no-boundary proposal itself: the question "what happened before the Big Bang?" is not answered but dissolved — by recognizing that "before" has no meaning when there is no boundary. The cosmological and the autobiographical share a common structure: the apparent limiting condition turns out not to be a boundary at all.

Important concepts

ALS (amyotrophic lateral sclerosis)

The progressive motor neurone disease with which Hawking was diagnosed in 1962–63 at the age of twenty-one. The disease destroys the motor neurons that control voluntary muscle movement, resulting in progressive paralysis while leaving cognition unaffected. Hawking had an unusually slow-progressing form; most ALS patients survive two to five years after diagnosis; he survived fifty-five years.

Singularity

A point in spacetime where the curvature of space becomes infinite and the equations of general relativity break down. The Big Bang and the centres of black holes are the two primary contexts in which singularities appear. Hawking's singularity theorems (with Penrose and Geroch) established that singularities are not mathematical artifacts of special assumptions but generic predictions of general relativity under physically realistic conditions.

Event horizon

The boundary of a black hole: the surface beyond which the escape velocity exceeds the speed of light. Nothing that crosses the event horizon from inside can return to the outside. The event horizon is not a material surface but a geometric feature of the spacetime metric — a one-way membrane.

Hawking radiation

The thermal radiation predicted by Hawking in 1974 to be emitted by black holes as a consequence of quantum effects near the event horizon. The temperature of this radiation is inversely proportional to the black hole's mass. The prediction combines general relativity, quantum field theory, and thermodynamics in a single calculation and implies that black holes slowly evaporate.

Area theorem

Hawking's 1970 result that the total area of a black hole's event horizon cannot decrease in any physical process. The formal analogy with the second law of thermodynamics (entropy never decreases) was the first hint that black holes have a thermodynamic description, subsequently made precise by Bekenstein's identification of horizon area with entropy and Hawking's radiation calculation.

No-hair theorem

The result that a stationary black hole is completely characterized by three parameters: mass, electric charge, and angular momentum. All information about the matter that formed the black hole is inaccessible from outside. Proved by Hawking, Brandon Carter, and David Robinson.

Black hole information paradox

The question of whether information about the quantum state of matter that falls into a black hole is permanently lost when the black hole evaporates via Hawking radiation, or whether it is encoded in the outgoing radiation. Quantum mechanics requires that information is not destroyed; Hawking radiation, being thermal, appears to carry no specific information. The paradox is unresolved and remains one of the central open problems in theoretical physics.

Imaginary time

The mathematical device of replacing real time t with it (where i = √−1) in the equations of physics. In imaginary time, the spacetime metric becomes Euclidean (positive definite) rather than Lorentzian; singularities are smoothed out; and the path integrals of quantum mechanics become better defined. Hawking uses imaginary time as the technical foundation of the no-boundary proposal.

No-boundary proposal (Hartle–Hawking state)

The 1983 proposal by Stephen Hawking and James Hartle that the wave function of the universe is given by a path integral over all compact, smooth, four-dimensional Euclidean geometries — geometries with no boundary. In imaginary time, the universe has no edge and no beginning; the Big Bang is a smooth interior point, not a singularity. The proposal eliminates the need for initial boundary conditions for the universe.

Chronology protection conjecture

Hawking's 1992 conjecture that the laws of physics prevent the formation of closed timelike curves on macroscopic scales, thereby preventing time travel to the past. The proposed mechanism is that quantum vacuum fluctuations build up divergently near a potential Cauchy horizon, destroying any incipient time machine before it can form.

Steady-state theory

The cosmological model, proposed in 1948 by Hoyle, Gold, and Bondi, holding that the universe is in a steady state with no beginning and no end, with new matter continuously created to maintain constant average density as the universe expands. The discovery of the cosmic microwave background in 1965 provided strong evidence against the theory, and the singularity theorems of Hawking and Penrose showed that an expanding universe satisfying general relativity's energy conditions necessarily had a singular beginning.

Cosmic microwave background (CMB)

The thermal radiation left over from the early universe, first detected by Penzias and Wilson in 1965. With a temperature of approximately 2.7 K, the CMB is the cooled remnant of the hot, dense state of the early universe. Its existence is a central prediction of Big Bang cosmology and a principal piece of evidence against the steady-state theory.

References and Web Links

Primary book and edition information

• Hawking, Stephen. My Brief History. Bantam Books, 2013 (US); Bantam Press, 2013 (UK). 144 pp. ISBN 978-0-345-53528-3.
  • Penguin Random House book page
  • Open Library record
  • Amazon US listing (hardcover)

Background and overview

• Wikipedia: My Brief History
• Wikipedia: Stephen Hawking — full biographical article
• Caltech obituary: Caltech Mourns the Loss of Stephen Hawking

Hawking radiation and black hole thermodynamics

• Hawking, S. W. "Black hole explosions?" Nature 248 (1974): 30–31. The original paper predicting Hawking radiation.
• Bekenstein, Jacob. "Black Holes and Entropy." Physical Review D 7 (1973): 2333. The paper establishing that black hole entropy is proportional to horizon area.
• Wikipedia: Hawking radiation
• Kip Thorne's Westminster tribute to Stephen Hawking — Caltech (PDF)

Singularity theorems

• Penrose, Roger. "Gravitational Collapse and Space-Time Singularities." Physical Review Letters 14 (1965): 57–59.
• Hawking, S. W., and R. Penrose. "The Singularities of Gravitational Collapse and Cosmology." Proceedings of the Royal Society A 314 (1970): 529–548.

The no-boundary proposal and imaginary time

• Hartle, J. B., and S. W. Hawking. "Wave function of the Universe." Physical Review D 28 (1983): 2960. The original paper.
• Quanta Magazine: Physicists Debate Hawking's Idea That the Universe Had No Beginning
• Physics LibreTexts: The Hartle-Hawking no-boundary proposal

Chronology protection conjecture

• Hawking, S. W. "Chronology protection conjecture." Physical Review D 46 (1992): 603–611.
• Wikipedia: Chronology protection conjecture

A Brief History of Time (discussed in Chapter 10)

• Wikipedia: A Brief History of Time
• Slate: How A Brief History of Time Changed Our Perception of Physics
• National Academies chapter on writing of A Brief History of Time (from "Stephen Hawking: A Life in Science")

Reviews and critical reception

• Kirkus Reviews: My Brief History

Additional study resources

These are secondary summaries and should be used alongside, rather than instead of, the original book.

• Wikipedia: Jane Hawking — for context on the marriage chapters
• Royal Society: Stephen William Hawking biographical memoir