Scientifically,
Dr. Hawking will be best remembered for a discovery so strange that it
might be expressed in the form of a Zen koan: When is a black hole not
black? When it explodes.
What
is equally amazing is that he had a career at all. As a graduate
student in 1963, he learned he had amyotrophic lateral sclerosis, a
neuromuscular wasting disease also known as Lou Gehrig’s disease. He was
given only a few years to live.
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The
disease reduced his bodily control to the flexing of a finger and
voluntary eye movements but left his mental faculties untouched.
He went on to become his generation’s leader in exploring gravity and the properties of black holes, the bottomless gravitational pits so deep and dense that not even light can escape them.
That
work led to a turning point in modern physics, playing itself out in
the closing months of 1973 on the walls of his brain when Dr. Hawking
set out to apply quantum theory, the weird laws that govern subatomic
reality, to black holes. In a long and daunting calculation, Dr. Hawking
discovered to his befuddlement that black holes — those mythological
avatars of cosmic doom — were not really black at all. In fact, he
found, they would eventually fizzle, leaking radiation and particles,
and finally explode and disappear over the eons.
The Expansive Life of Stephen Hawking
CreditPaul E. Alers/NASA
Nobody,
including Dr. Hawking, believed it at first — that particles could be
coming out of a black hole. “I wasn’t looking for them at all,” he
recalled in 1978. “I merely tripped over them. I was rather annoyed.”
That calculation, in a thesis published in 1974 in the journal Nature under the title “Black Hole Explosions?,”
is hailed by scientists as the first great landmark in the struggle to
find a single theory of nature — to connect gravity and quantum
mechanics, those warring descriptions of the large and the small, to
explain a universe that seems stranger than anybody had thought.
The
discovery of Hawking radiation, as it is known, turned black holes
upside down. It transformed them from destroyers to creators — or at
least to recyclers — and wrenched the dream of a final theory in a strange, new direction.
“You
can ask what will happen to someone who jumps into a black hole,” Dr.
Hawking said in 1978. “I certainly don’t think he will survive it.
“On
the other hand,” he added, “if we send someone off to jump into a black
hole, neither he nor his constituent atoms will come back, but his mass
energy will come back. Maybe that applies to the whole universe.”
Dennis
W. Sciama, a cosmologist and Dr. Hawking’s thesis adviser at Cambridge,
called Hawking’s thesis in Nature “the most beautiful paper in the
history of physics.”
Edward
Witten, a theorist at the Institute for Advanced Study in Princeton,
said: “Trying to understand Hawking’s discovery better has been a source
of much fresh thinking for almost 40 years now, and we are probably
still far from fully coming to grips with it. It still feels new.”
In 2002, Dr. Hawking said he wanted the formula for Hawking radiation to be engraved on his tombstone.
He was a man who pushed the limits — in his intellectual life, to be sure, but also in his professional
and personal lives. He traveled the globe to scientific meetings,
visiting every continent, including Antarctica; wrote best-selling books
about his work; married twice; fathered three children; and was not
above appearing on “The Simpsons,” “Star Trek: The Next Generation” or “The Big Bang Theory.”
He
celebrated his 60th birthday by going up in a hot-air balloon. The same
week, he also crashed his electric-powered wheelchair while speeding
around a corner in Cambridge, breaking his leg.
In
April 2007, a few months after his 65th birthday, he took part in a
zero-gravity flight aboard a specially equipped Boeing 727, a padded
aircraft that flies a roller-coaster trajectory to produce fleeting
periods of weightlessness. It was a prelude to a hoped-for trip to space
with Richard Branson’s Virgin Galactic company aboard SpaceShipTwo.
Asked why he took such risks,
Dr. Hawking said, “I want to show that people need not be limited by
physical handicaps as long as they are not disabled in spirit.”
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His own spirit left many in awe.
“What
a triumph his life has been,” said Martin Rees, a Cambridge University
cosmologist, the astronomer royal of England and Dr. Hawking’s longtime
colleague. “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 willpower
and determination.”
Studies Came Easy
Stephen
William Hawking was born in Oxford, England, on Jan. 8, 1942 — 300
years to the day, he liked to point out, after the death of Galileo, who
had begun the study of gravity. His mother, the former Isobel Walker,
had gone to Oxford to avoid the bombs that fell nightly during the Blitz
of London. His father, Frank Hawking, was a prominent research
biologist.
The
oldest of four children, Stephen was a mediocre student at St. Albans
School in London, though his innate brilliance was recognized by some
classmates and teachers.
Later,
at University College, Oxford, he found his studies in mathematics and
physics so easy that he rarely consulted a book or took notes. He got by
with a thousand hours of work in three years, or one hour a day, he
estimated. “Nothing seemed worth making an effort for,” he said.
The
only subject he found exciting was cosmology because, he said, it dealt
with “the big question: Where did the universe come from?”
Who Was Stephen W. Hawking?
- Stephen W. Hawking was born in Oxford, England, on Jan. 8, 1942.
- At 21, he was diagnosed with amyotrophic lateral sclerosis, also known as Lou Gehrig’s disease, and was told he had less than three years to live.
- He was a renowned Cambridge University physicist and best-selling author who visited every continent and married twice, fathering three children.
- He produced some of the most important cosmological research of his time about gravity and the properties of black holes.
He
moved to Cambridge upon his graduation from Oxford. Before he could
begin his research, however, he was stricken by what his research
adviser, Dr. Sciama, came to call “that terrible thing.”
The
young Hawking had been experiencing occasional weakness and falling
spells for several years. Shortly after his 21st birthday, in 1963,
doctors told him that he had amyotrophic lateral sclerosis. They gave
him less than three years to live.
His
first response was severe depression. He dreamed he was going to be
executed, he said. Then, against all odds, the disease appeared to
stabilize. Though he was slowly losing control of his muscles, he was
still able to walk short distances and perform simple tasks, though
laboriously, like dressing and undressing. He felt a new sense of
purpose.
“When
you are faced with the possibility of an early death,” he recalled, “it
makes you realize that life is worth living and that there are a lot of
things you want to do.”
In
1965, he married Jane Wilde, a student of linguistics. Now, by his own
account, he not only had “something to live for”; he also had to find a
job, which gave him an incentive to work seriously toward his doctorate.
His
illness, however, had robbed him of the ability to write down the long
chains of equations that are the tools of the cosmologist’s trade.
Characteristically, he turned this handicap into a strength, gathering
his energies for daring leaps of thought, which, in his later years, he
often left for others to codify in proper mathematical language.
“People
have the mistaken impression that mathematics is just equations,” Dr.
Hawking said. “In fact, equations are just the boring part of
mathematics.”
By
necessity, he concentrated on problems that could be attacked through
“pictures and diagrams,” adopting geometric techniques that had been
devised in the early 1960s by the mathematician Roger Penrose and a
fellow Cambridge colleague, Brandon Carter, to study general relativity,
Einstein’s theory of gravity.
Black
holes are a natural prediction of that theory, which explains how mass
and energy “curve” space, the way a sleeping person causes a mattress to
sag. Light rays will bend as they traverse a gravitational field, just
as a marble rolling on the sagging mattress will follow an arc around
the sleeper.
Too
much mass or energy in one spot could cause space to sag without end;
an object that was dense enough, like a massive collapsing star, could
wrap space around itself like a magician’s cloak and disappear,
shrinking inside to a point of infinite density called a singularity, a
cosmic dead end, where the known laws of physics would break down: a
black hole.
Einstein himself thought this was absurd when the possibility was pointed out to him.
Using
the Hubble Space Telescope and other sophisticated tools of observation
and analysis, however, astronomers have identified hundreds of objects
that are too massive and dark to be anything but black holes, including a
supermassive one at the center of the Milky Way. According to current
theory, the universe should contain billions more.
As
part of his Ph.D. thesis in 1966, Dr. Hawking showed that when you ran
the film of the expanding universe backward, you would find that such a
singularity had to have existed sometime in cosmic history; space and
time, that is, must have had a beginning. He, Dr. Penrose and a rotating
cast of colleagues published a series of theorems about the behavior of
black holes and the dire fate of anything caught in them.
A Calculation in His Head
Dr. Hawking’s signature breakthrough resulted from a feud with the Israeli theoretical physicist Jacob Bekenstein,
then a Princeton graduate student, about whether black holes could be
said to have entropy, a thermodynamic measure of disorder. Dr.
Bekenstein said they could, pointing out a close analogy between the
laws that Dr. Hawking and his colleagues had derived for black holes and
the laws of thermodynamics.
Dr.
Hawking said no. To have entropy, a black hole would have to have a
temperature. But warm objects, from a forehead to a star, radiate a
mixture of electromagnetic radiation, depending on their exact
temperatures. Nothing could escape a black hole, and so its temperature
had to be zero. “I was very down on Bekenstein,” Dr. Hawking recalled.
To
settle the question, Dr. Hawking decided to investigate the properties
of atom-size black holes. This, however, required adding quantum
mechanics, the paradoxical rules of the atomic and subatomic world, to
gravity, a feat that had never been accomplished. Friends turned the
pages of quantum theory textbooks as Dr. Hawking sat motionless staring
at them for months. They wondered if he was finally in over his head.
When
he eventually succeeded in doing the calculation in his head, it
indicated to his surprise that particles and radiation were spewing out
of black holes. Dr. Hawking became convinced that his calculation was
correct when he realized that the outgoing radiation would have a
thermal spectrum characteristic of the heat radiated by any warm body,
from a star to a fevered forehead. Dr. Bekenstein had been right.
Dr.
Hawking even figured out a way to explain how particles might escape a
black hole. According to quantum principles, the space near a black hole
would be teeming with “virtual” particles that would flash into
existence in matched particle-and-antiparticle pairs — like electrons
and their evil twin opposites, positrons — out of energy borrowed from
the hole’s intense gravitational field.
They
would then meet and annihilate each other in a flash of energy,
repaying the debt for their brief existence. But if one of the pair fell
into the black hole, the other one would be free to wander away and
become real. It would appear to be coming from the black hole and taking
energy away from it.
But those, he cautioned, were just words. The truth was in the math.
“The
most important thing about Hawking radiation is that it shows that the
black hole is not cut off from the rest of the universe,” Dr. Hawking
said.
It
also meant that black holes had a temperature and had entropy. In
thermodynamics, entropy is a measure of wasted heat. But it is also a
measure of the amount of information — the number of bits — needed to
describe what is in a black hole. Curiously, the number of bits is
proportional to the black hole’s surface area, not its volume, meaning
that the amount of information you could stuff into a black hole is
limited by its area, not, as one might think, its volume.
That
result has become a litmus test for string theory and other pretenders
to a theory of quantum gravity. It has also led to speculations that we
live in a holographic universe, in which three-dimensional space is some
kind of illusion.
Andrew
Strominger, a Harvard string theorist, said of the holographic theory,
“If it’s really true, it’s a deep and beautiful property of our universe
— but not an obvious one.”
To ‘Know the Mind of God’
The
discovery of black hole radiation also led to a 30-year controversy
over the fate of things that had fallen into a black hole.
Dr.
Hawking initially said that detailed information about whatever had
fallen in would be lost forever because the particles coming out would
be completely random, erasing whatever patterns had been present when
they first fell in. Paraphrasing Einstein’s complaint about the
randomness inherent in quantum mechanics, Dr. Hawking said, “God not
only plays dice with the universe, but sometimes throws them where they
can’t be seen.”
Many
particle physicists protested that this violated a tenet of quantum
physics, which says that knowledge is always preserved and can be
retrieved. Leonard Susskind, a Stanford physicist who carried on the
argument for decades, said, “Stephen correctly understood that if this
was true, it would lead to the downfall of much of 20th-century
physics.”
On
another occasion, he characterized Dr. Hawking to his face as “one of
the most obstinate people in the world; no, he is the most infuriating
person in the universe.” Dr. Hawking grinned.
Dr.
Hawking admitted defeat in 2004. Whatever information goes into a black
hole will come back out when it explodes. One consequence, he noted
sadly, was that one could not use black holes to escape to another
universe. “I’m sorry to disappoint science fiction fans,” he said.
Despite
his concession, however, the information paradox, as it is known, has
become one of the hottest topics in theoretical physics. Physicists say
they still do not know how information gets in or out of black holes.
An Earthling’s Guide to Black Holes
Welcome to the place of no return — a region in space
where the gravitational pull is so strong that not even light can escape
it. This is a black hole.
Raphael
Bousso of the University of California, Berkeley, and a former student
of Dr. Hawking’s, said the present debate had raised “by another few
notches” his estimation of the “stupendous magnitude” of Dr. Hawking’s
original discovery.
In
1974, Dr. Hawking was elected a Fellow of the Royal Society, the
world’s oldest scientific organization; in 1979, he was appointed to the
Lucasian chair of mathematics at Cambridge, a post once held by Isaac
Newton. “They say it’s Newton’s chair, but obviously it’s been changed,”
he liked to quip.
Dr.
Hawking also made yearly visits to the California Institute of
Technology in Pasadena, which became like a second home. In 2008, he
joined the Perimeter Institute for Theoretical Physics in Waterloo,
Ontario, as a visiting researcher.
Having
conquered black holes, Dr. Hawking set his sights on the origin of the
universe and on eliminating that pesky singularity at the beginning of
time from models of cosmology. If the laws of physics could break down
there, they could break down everywhere.
In
a meeting at the Vatican in 1982, he suggested that in the final theory
there should be no place or time when the laws broke down, even at the
beginning. He called the notion the “no boundary” proposal.
With
James Hartle of the Institute for Theoretical Physics in Santa Barbara,
Calif., Dr. Hawking envisioned the history of the universe as a sphere
like the Earth. Cosmic time corresponds to latitude, starting with zero
at the North Pole and progressing southward.
Although
time started there, the North Pole was nothing special; the same laws
applied there as everywhere else. Asking what happened before the Big
Bang, Dr. Hawking said, was like asking what was a mile north of the
North Pole — it was not any place, or any time.
By
then, string theory, which claimed finally to explain both gravity and
the other forces and particles of nature as tiny microscopically
vibrating strings, like notes on a violin, was the leading candidate for
a “theory of everything.”
In
“A Brief History of Time,” Dr. Hawking concluded that “if we do
discover a complete theory” of the universe, “it should in time be
understandable in broad principle by everyone, not just a few
scientists.”
He
added, “Then we shall all, philosophers, scientists and just ordinary
people, be able to take part in the discussion of why it is that we and
the universe exist.”
“If
we find the answer to that,” he continued, “it would be the ultimate
triumph of human reason — for then we would know the mind of God.”
Dr. Hawking
Until
1974, Dr. Hawking was still able to feed himself and to get in and out
of bed. At Jane’s insistence, he would drag himself, hand over hand, up
the stairs to the bedroom in his Cambridge home every night, in an
effort to preserve his remaining muscle tone. After 1980, care was
supplemented by nurses.
Dr.
Hawking retained some control over his speech up to 1985. But on a trip
to Switzerland, he came down with pneumonia. The doctors asked Jane if
she wanted his life support turned off, but she said no. To save his
life, doctors inserted a breathing tube. He survived, but his voice was
permanently silenced.
Speaking With the Eyes
It
appeared for a time that he would be able to communicate only by
pointing at letters on an alphabet board. But when a computer expert,
Walter Woltosz, heard about Dr. Hawking’s condition, he offered him a
program he had written called Equalizer. By clicking a switch with his
still-functioning fingers, Dr. Hawking was able to browse through menus
that contained all the letters and more than 2,500 words.
Word
by word — and when necessary, letter by letter — he could build up
sentences on the computer screen and send them to a speech synthesizer
that vocalized for him. The entire apparatus was fitted to his motorized
wheelchair.
Even
when too weak to move a finger, he communicated through the computer by
way of an infrared beam, which he activated by twitching his right
cheek or blinking his eye. The system was expanded to allow him to open
and close the doors in his office and to use the telephone and internet
without aid.
Although
he averaged fewer than 15 words per minute, Dr. Hawking found he could
speak through the computer better than he had before losing his voice.
His only complaint, he confided, was that the speech synthesizer,
manufactured in California, gave him a new vocal inflection.
“Please pardon my American accent,” he used to say.
His
decision to write “A Brief History of Time” was prompted, he said, by a
desire to share his excitement about “the discoveries that have been
made about the universe” with “the public that paid for the research.”
He wanted to make the ideas so accessible that the book would be sold in
airports.
He
also hoped to earn enough to pay for his children’s education. He did.
The book’s extraordinary success made him wealthy, a hero to disabled
people everywhere and even more famous.
The
news media followed his movements and activities over the years, from
visiting the White House to meeting the Dallas Cowboys cheerleaders, and
reported his opinions on everything from national health care
(socialized medicine in England had kept him alive) to communicating
with extraterrestrials (maybe not a good idea, he said), as if he were a
rolling Delphic Oracle.
Asked by New Scientist magazine what he thought about most, Dr. Hawking answered: “Women. They are a complete mystery.”
In
1990, Dr. Hawking and his wife separated after 25 years of marriage;
Jane Hawking wrote about their years together in two books, “Music to
Move the Stars: A Life With Stephen Hawking” and “Traveling to Infinity:
My Life With Stephen.” The latter became the basis of the movie “The Theory of Everything.”
In
1995, he married Elaine Mason, a nurse who had cared for him since his
bout of pneumonia. She had been married to David Mason, the engineer who
had attached Dr. Hawking’s speech synthesizer to his wheelchair.
In 2004,
British newspapers reported that the Cambridge police were
investigating allegations that Elaine had abused Dr. Hawking, but no
charges were filed, and Dr. Hawking denied the accusations. They later divorced.
His survivors include his children, Robert, Lucy and Tim, and three grandchildren.
‘There Is No Heaven’
Among
his many honors, Dr. Hawking was named a commander of the British
Empire in 1982. In the summer of 2012, he had a star role in the opening
of the Paralympics Games in London. The only thing lacking was the
Nobel Prize, and his explanation for this was characteristically pithy:
“The Nobel is given only for theoretical work that has been confirmed by
observation. It is very, very difficult to observe the things I have
worked on.”
Dr.
Hawking was a strong advocate of space exploration, saying it was
essential to the long-term survival of the human race. “Life on Earth is
at the ever-increasing risk of being wiped out by a disaster, such as
sudden global nuclear war, a genetically engineered virus or other
dangers we have not yet thought of,” he told an audience in Hong Kong in
2007.
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Nothing
raised as much furor, however, as his increasingly scathing remarks
about religion. One attraction of the no-boundary proposal for Dr.
Hawking was that there was no need to appeal to anything outside the
universe, like God, to explain how it began.
In
“A Brief History of Time,” he had referred to the “mind of God,” but in
“The Grand Design,” a 2011 book he wrote with Leonard Mlodinow, he was
more bleak about religion. “It is not necessary to invoke God to light
the blue touch paper,” he wrote, referring to the British term for a
firecracker fuse, “and set the universe going.”
He went further that year, telling The Guardian:
“I regard the brain as a computer which will stop working when its
components fail. There is no heaven or afterlife for broken-down
computers; that is a fairy story for people afraid of the dark.”
Having spent the best part of his life grappling with black holes and cosmic doom, Dr. Hawking had no fear of the dark.
“They’re
named black holes because they are related to human fears of being
destroyed or gobbled up,” he once told an interviewer. “I don’t have
fears of being thrown into them. I understand them. I feel in a sense
that I am their master.”
Correction: March 14, 2018
An earlier version of this obituary misstated the year Dr. Hawking was appointed to the Lucasian chair of mathematics at Cambridge University. It was 1979, not 1982. The earlier version also misstated part of the title of Martin Rees, a longtime colleague of Dr. Hawking’s. He is the astronomer royal of England, not Britain.
An earlier version of this obituary misstated the year Dr. Hawking was appointed to the Lucasian chair of mathematics at Cambridge University. It was 1979, not 1982. The earlier version also misstated part of the title of Martin Rees, a longtime colleague of Dr. Hawking’s. He is the astronomer royal of England, not Britain.
