A short history of Stephen. The structure of the Universe - in simple terms

Acknowledgments

The book is dedicated to Jane

I decided to try to write a popular book about space and time after I gave the Loeb Lectures at Harvard in 1982. At that time there were already quite a few books devoted to the early Universe and black holes, both very good, for example Steven Weinberg’s book “The First Three Minutes,” and very bad, which there is no need to name here. But it seemed to me that none of them actually addressed the questions that prompted me to study cosmology and quantum theory: where did the universe come from? how and why did it arise? will it end, and if it does, how? These questions interest us all. But modern science is very rich in mathematics, and only a few specialists have sufficient knowledge of the latter to understand this. However, the basic ideas about the birth and further fate of the Universe can be presented without the help of mathematics in such a way that they will become understandable even to people who have not received a scientific education. This is what I tried to do in my book. It is up to the reader to judge how successful I am.

I was told that every formula included in the book would cut the number of buyers in half. Then I decided to do without formulas altogether. True, in the end I still wrote one equation - the famous Einstein equation E=mc^2. I hope it doesn't scare off half of my potential readers.

Apart from the fact that I fell ill with amyotrophic lateral sclerosis, then in almost everything else I was lucky. The help and support I received from my wife Jane and my children Robert, Lucy and Timothy enabled me to lead a fairly normal life and achieve success at work. I was also lucky in that I chose theoretical physics, because it all fits in my head. Therefore, my physical weakness did not become a serious disadvantage. My scientific colleagues, without exception, always provided me with maximum assistance.

During the first, “classic” stage of my work, my closest assistants and collaborators were Roger Penrose, Robert Gerok, Brandon Carter and George Ellis. I am grateful to them for their help and for their collaboration. This stage ended with the publication of the book “Large-scale structure of space-time,” which Ellis and I wrote in 1973 (S. Hawking, J. Ellis. Large-scale structure of space-time. M.: Mir, 1976).

During the second, "quantum" phase of my work, which began in 1974, I worked primarily with Gary Gibbons, Don Page, and Jim Hartle. I owe a lot to them, as well as to my graduate students, who provided me with enormous help both in the “physical” and in the “theoretical” sense of the word. The need to keep up with graduate students was an extremely important motivator and, I think, kept me from getting stuck in a mire.

Brian Witt, one of my students, helped me a lot while working on the book. In 1985, after sketching out the first rough outline of the book, I fell ill with pneumonia. I had to undergo surgery, and after the tracheotomy I stopped speaking, and thus almost lost the ability to communicate. I thought I wouldn't be able to finish the book. But Brian not only helped me revise it, but also taught me how to use the Living Center computer communication program, which was given to me by Walt Waltosh, an employee of Words Plus, Inc., Sunnyvale, California. With its help, I can write books and articles, and also talk to people through a speech synthesizer given to me by another Sunnyvale company, Speech Plus. David Mason installed this synthesizer and a small personal computer on my wheelchair. This system changed everything: it became even easier for me to communicate than before I lost my voice.

What is Stephen Hawking's A Brief History of Time about?

From open sources

Today, March 14, the famous English theoretical physicist Stephen Hawking died at the age of 77. the site publishes a synopsis of his popular science book “A Brief History of Time: From the Big Bang to Black Holes” (1988), which became a bestseller

The book by the outstanding English physicist Stephen Hawking, “A Brief History of Time: From the Big Bang to Black Holes,” is dedicated to finding the answer to Einstein’s question: “What choice did God have when he created the Universe?” Warned that every formula included in the book would halve the number of buyers, Hawking lays out in accessible language the ideas of quantum theory of gravity, an as-yet-unfinished branch of physics that combines general relativity and quantum mechanics.

The book begins with a story about the evolution of human ideas about the Universe: from the celestial spheres of the geocentric system of Aristotle and Ptolemy to the realization of the fact that the Sun is an ordinary yellow star of average size in one of the arms of a spiral galaxy - among hundreds of billions of other galaxies in the observable part of the Universe. The discovery of the redshift of the spectra of stars in other galaxies meant that the Universe was expanding, and this led to the big bang hypothesis: ten or twenty billion years ago, all objects in the Universe could be located in one place with an infinitely high density (singularity point).

News on the topic

The Big Bang serves as the beginning of time. There is no answer to the question of what happened before the Big Bang, since scientific laws stop working at the point of singularity; the ability to predict the future is lost, and therefore, if something happened “before”, it will not affect current events in any way. After the Big Bang, two scenarios are possible: either the expansion of the Universe will continue forever, or at some point it will stop and go into a compression phase, which will end with a return to the singularity - the Big Bang. It is unclear which option will be realized - it depends on the distances between galaxies and the total mass of matter in the Universe, and these quantities are not precisely known.

Singularities can exist in the Universe even after the Big Bang. A star, having used up nuclear fuel, begins to shrink, and with a sufficiently large mass it cannot resist gravitational collapse, turning into a black hole. So, the English mathematician and physicist Roger Penrose showed that the volume of the star tends to zero, and the density of its matter and the curvature of space-time tend to infinity. In other words, a black hole is a singularity in space-time.

By reversing the direction of time, Penrose and Hawking proved the claim that if general relativity (GR) is true, then the Big Bang point must exist. So the big bang hypothesis became a mathematical theorem, and general relativity itself turned out to be incomplete: its laws are violated at the singularity point. This is not surprising - after all, GTR is a classical theory, and in a small region of space near the singularity, quantum effects become significant. Thus, the study of black holes and the early Universe requires the use of quantum mechanics and the creation of a unified theory - the quantum theory of gravity.

Dealing with the phenomena of the microworld, quantum mechanics developed independently of general relativity. Quantum physics has accumulated some experience in combining different types of interactions. Thus, it was possible to combine electromagnetic and weak interactions into one theory. Namely, it turned out that the carriers of electromagnetic interaction (virtual photons) and the carriers of weak interaction (vector bosons) are realizations of one particle and become indistinguishable from each other at energies of about 100 GeV. There are also grand unification theories, that is, the unification of the electroweak and strong interactions (however, to achieve the energies of the grand unification and test these theories, an accelerator the size of the Solar System is needed).

All these theories do not include gravity, since it is very small for elementary particles. However, at the point of singularity, gravitational forces, together with the curvature of space-time, tend to infinity, so that the joint consideration of quantum mechanical and gravitational effects becomes inevitable. This leads to the following surprising results.

According to the Penrose–Hawking theorem, falling into a black hole is irreversible. But, as is known, every irreversible process is accompanied by an increase in entropy. Does a black hole have entropy?

Hawking notes that the area of the event horizon of a black hole does not decrease with time (and when matter falls into a black hole, it increases), that is, it has all the properties of entropy. His American colleague Bikenstein proposes that the area of a black hole's event horizon be considered a measure of its entropy. Hawking objects: having entropy, a black hole must have a temperature and therefore radiate - contrary to the very definition of a black hole! - but later he himself discovers the mechanism of this radiation.

The source of radiation turns out to be a vacuum near a black hole, in which particle-antiparticle pairs are born due to quantum fluctuations of energy. One member of the pair has positive energy, the other has negative energy (so the sum is zero); a particle with negative energy can fall into a black hole, and a particle with positive energy can leave its vicinity. The flow of positive energy particles is the radiation of the black hole; particles with negative energy reduce its mass - the black hole “evaporates” and disappears over time, taking the singularity with it. Hawking sees this as the first indication of the possibility of eliminating the singularities of general relativity using quantum mechanics and asks the question: will quantum mechanics have a similar effect on the “big” singularities, that is, will quantum mechanics eliminate the singularities of the Big Bang and the Big Bang?

News on the topic

The classical general theory of relativity leaves no choice: the expanding Universe is born from a singularity, and the initial conditions are unknown (GTR does not work at the “moment of creation”). At the initial moment, the Universe could be ordered and homogeneous, or it could be very chaotic. The further process of evolution, however, significantly depends on the conditions at this boundary of space-time. Using Feynman's method of summing over various "trajectories" of the development of the Universe, Hawking, within the framework of the quantum theory of gravity, obtains an alternative to singularity: space-time is finite and does not have a singularity in the form of a boundary or edge (it is similar to the surface of the Earth, but only in four dimensions) . And since there is no boundary, there is no need for initial conditions on it, that is, there is no need to introduce new laws that determine the behavior of the early Universe (or resort to the help of God). Then the Universe "...would not have been created, it could not be destroyed. It would simply exist."

The theme of God is present throughout the book; Hawking is essentially having a discussion with God. Here is a quote that kind of sums up this discussion.

“From the idea that space and time form a closed surface, very important consequences also follow regarding the role of God in the life of the Universe. In connection with the successes achieved by scientific theories in describing events, most scientists have come to the conviction that God allows the Universe to develop in according to a certain system of laws and does not interfere with its development, does not violate these laws. But the laws do not tell us anything about what the Universe looked like when it first appeared - winding the clock and choosing the beginning could still be the work of God. While we think that the Universe had a beginning, we can think that it had a Creator, but if the Universe is truly completely closed and has no boundaries or edges, then it should have neither a beginning nor an end: it simply is ", and that's all! Is there then any place left for the Creator?"

Here is the answer to Einstein’s question: God did not have any freedom to choose the initial conditions.

By summing over Feynman trajectories in the absence of space-time boundaries, Hawking finds that the Universe in its current state is highly likely to expand equally quickly in all directions - in agreement with observations of the isotropic background of the CMB. Further, since the origin of time is a smooth, regular point in space and time, then the Universe began its evolution from a homogeneous, ordered state. This initial order explains the presence of a thermodynamic arrow of time, indicating the direction of time in which the disorder (entropy) of the Universe increases.

In the final part of the book, Hawking describes string theory, which claims to unify all physics. This theory does not deal with particles, but with objects like one-dimensional strings. Particles are interpreted as vibrations of strings, emission and absorption of particles - as breaking and joining of strings. String theory, however, does not lead to contradictions only in 10-dimensional or 26-dimensional spaces. Perhaps, during the development of the Universe, only four coordinates of our space-time “unfolded,” while the rest turned out to be folded into a space of negligibly small sizes.

Why did it happen? Hawking gives the answer from the standpoint of the so-called anthropic principle: otherwise the conditions for the development of intelligent beings capable of asking such a question would not have arisen. In fact, in the case of a smaller dimension of space, evolution is difficult: for example, every through passage in the body of a two-dimensional creature divides it into two parts. In spaces of higher dimensions, the law of gravitational attraction will be different, and the orbits of the planets will become unstable (“we would then either freeze or burn”). Of course, other universes are also possible, with a different number of unfolded coordinates, “... but in such areas there will be no intelligent beings who could see this variety of operating dimensions.”

Hawking is optimistic about the prospects for creating a unified theory that describes the Universe. Having taken away the act of creation from God, he assigns God the role of the creator of its laws. When a mathematical model is built, the question remains why the Universe, which obeys this model, exists at all. Unbound by the need to build new theories, scientists will turn to its research. “And if the answer to such a question is found, it will be a complete triumph of human reason, for then God’s plan will become clear to us.”

Summary of Stephen Hawking's book "A Brief History of Time" prepared by Igor Yakovlev

Stephen Hawking, Leonard Mlodinow

Brief history of time

Preface

Only four letters distinguish the title of this book from the title of the one first published in 1988. “A Brief History of Time” remained on the London Sunday Times bestseller list for 237 weeks, and every 750th person on our planet, adult or child, purchased it. A remarkable success for a book devoted to the most difficult problems of modern physics. However, these are not only the most difficult, but also the most exciting problems, because they address us to fundamental questions: what do we really know about the Universe, how did we acquire this knowledge, where did the Universe come from and where is it going? These questions formed the main subject of A Brief History of Time and became the focus of this book. A year after the publication of A Brief History of Time, responses began to pour in from readers of all ages and backgrounds around the world. Many of them expressed the wish for a new version of the book to be published that, while retaining the essence of A Brief History of Time, would explain the most important concepts in a simpler and more entertaining way. Although some may have expected it to be A Long History of Time, the response from readers made it clear that very few of them were eager to read a lengthy treatise that covered the subject at the level of a college course in cosmology. Therefore, while working on “The Shortest History of Time,” we preserved and even expanded the fundamental essence of the first book, but at the same time tried to leave its volume and accessibility of presentation unchanged. This is in fact shortest history, since we have omitted some purely technical aspects, however, as it seems to us, this gap is more than filled with a deeper interpretation of the material, which truly forms the core of the book.

We also took the opportunity to update the information and include the latest theoretical and experimental data in the book. A Brief History of Time describes the progress that has been made toward a complete unified theory in recent times. In particular, it concerns the latest provisions of string theory, wave-particle duality, and reveals the connection between various physical theories, indicating that a unified theory exists. As for practical research, the book contains important results of recent observations obtained, in particular, using the COBE (Cosmic Background Explorer) satellite and the Hubble Space Telescope.

Chapter first

THINKING ABOUT THE UNIVERSE

We live in a strange and wonderful universe. An extraordinary imagination is required to appreciate its age, size, fierceness and even beauty. The place occupied by people in this boundless space may seem insignificant. And yet we are trying to understand how this whole world works and how we, people, look in it.

Several decades ago, a famous scientist (some say it was Bertrand Russell) gave a public lecture on astronomy. He said that the Earth revolves around the Sun, and it, in turn, revolves around the center of a vast star system called our Galaxy. At the end of the lecture, a small old lady sitting in the back stood up and said:

You've been telling us complete nonsense here. In reality, the world is a flat slab resting on the back of a giant turtle.

Smiling with a feeling of superiority, the scientist asked:

What is the turtle standing on?

“You are a very smart young man, very much,” answered the old lady. - She stands on another turtle, and so on, ad infinitum!

Most people today would find this picture of the universe, this never-ending tower of turtles, quite funny. But what makes us think we know more?

Forget for a minute what you know—or think you know—about space. Look into the night sky. What do all these luminous points look like to you? Maybe they're tiny lights? It is difficult for us to guess what they really are, because this reality is too far from our everyday experience.

If you often watch the night sky, you've probably noticed an elusive spark of light just above the horizon at dusk. This is Mercury, a planet very different from our own. A day on Mercury lasts two-thirds of its year. On the sunny side, the temperature goes over 400°C, and in the dead of night it drops to almost -200°C.

But no matter how different Mercury is from our planet, it is even more difficult to imagine an ordinary star - a colossal inferno, burning millions of tons of matter every second and heated in the center to tens of millions of degrees.

Another thing that is hard to wrap your head around is the distances to planets and stars. The ancient Chinese built stone towers to get a closer look. It is quite natural to believe that stars and planets are much closer than they really are, since in everyday life we never come into contact with enormous cosmic distances.

These distances are so great that there is no point in expressing them in conventional units - meters or kilometers. Light years are used instead (a light year is the distance light travels in a year). In one second, a beam of light travels 300,000 kilometers, so a light year is a very long distance. The closest star to us (after the Sun), Proxima Centauri, is approximately four light years away. It is so far away that the fastest spacecraft currently being designed would take about ten thousand years to reach it. Even in ancient times, people tried to comprehend the nature of the Universe, but they did not have the capabilities that modern science, in particular mathematics, opens up. Today we have powerful tools: mental ones, such as mathematics and the scientific method, and technological ones, such as computers and telescopes. With their help, scientists have collected a huge amount of information about space. But what do we really know about the Universe and how did we know it? Where did she come from? In what direction is it developing? Did it have a beginning, and if it did, what happened? before him? What is the nature of time? Will it come to an end? Is it possible to go back in time? Recent major physics discoveries, enabled in part by new technologies, offer answers to some of these long-standing questions. Perhaps someday these answers will become as obvious as the Earth's revolution around the Sun - or perhaps as curious as a tower of turtles. Only time (whatever that is) will tell.

British scientist Stephen Hawking, known as the brightest star in modern astrophysics, has died at the age of 76.

Hawking is among the scientists who have had the greatest influence on our modern understanding of the universe with his study of black holes and popular science works such as A Brief History of Time. Born in 1942, the Briton was considered one of the world's greatest minds and was considered by some to be the most famous scientist in the modern world. For other scientists, he was a symbol of the unlimited possibilities of the human mind.

“His departure left an intellectual vacuum. But it's not empty. Think of it as a kind of energy penetrating the fabric of spacetime that cannot be measured." , world-renowned astrophysicist and science author Neil deGrasse Tyson tweeted.

At the age of 21, Professor Hawking was diagnosed with a rare form of motor neurone disease, and doctors gave him only a few years to live. His disease, however, progressed unusually slowly, causing him to work for more than half a century while confined to a wheelchair. In fact, Hawking was a medical miracle - only 5 percent of people who have this form of the disease live more than ten years after diagnosis, but he lived with it for more than five decades. He himself said that his physical condition was not a significant obstacle to his scientific work in the field of theoretical physics and even in some sense helped him.

Hawking lost his voice after severe pneumonia and complications. For a time, his only way of communicating was to spell words literally, raising his eyebrows when someone pointed to the correct letter on a special card. Later, a computer expert from California named Walt Waltow sent him his computer program called "Equalizer", with which the professor could select words from a menu on a screen controlled by a button in his hand. This, combined with a speech synthesizer, became Hawking's trademark "electronic" voice.

The illness did not interfere with his personal life. In 1965, he married his youthful love, Jane Wilde, although at that time he had already been diagnosed with a terrible disease. Their marriage lasted 26 years and ended in misunderstanding, but Hawking became the father of three children.

In 1995, he entered into his second marriage to Elaine Mason, a nurse who then took care of him. They remained together until 2006.
Hawking with his second wife Elaine Mason

The British scientist was known for his work on black holes and relativity, and is among the scientists who have most influenced the modern understanding of the Universe.

At the age of 17, Hawking received a place at Oxford. In 1971, together with Sir Roger Penrose, they provided a mathematical basis to support the Big Bang theory: they showed that if the theory of relativity is correct, then there must be a wormhole point in space-time. They also created the Hawking-Penrose theory of the early development of the universe after the Big Bang and its exponential expansion from a state of much higher temperature and density.
Hawking believed that the future of the human species lay in space.

Hawking also suggested that immediately after the Big Bang, primordial black holes formed and evaporated almost instantly. He later discovered that black holes emit energy and evaporate, a phenomenon that later became known as Hawking Radiation.

Over the years, he has worked on other theories about black holes, including the idea that they can lead to other universes.

In the early 1980s, he proposed that although the Universe has no boundaries, it has a finite size in spacetime. A mathematical proof of this theory was given a little later. According to him, the Universe is limitless, but finite.

Stephen Hawking's work in astrophysics places him among the most prestigious scientists in the world today. He was awarded 12 honorary titles, the Order of the British Empire and the US Presidential Medal of Freedom. For 30 years he was Lucasian Professor of Mathematics at Cambridge University, a position held by Isaac Newton and other famous scientists. Although Hawking retired in 2009, he continued to work at the university. Barack Obama presents Hawking with the US Presidential Medal of Freedom

His work in popularizing science brought him widespread fame and glory. A Brief History of Time, published in 1988, was a Sunday Times bestseller for 237 weeks - almost five years - with more than 10 million copies sold and translated into dozens of languages. The book describes in clear language the structure, origin and development of the Universe, exploring phenomena such as the Big Bang and the foundations of quantum mechanics.

In an interview with New Scientist shortly before his 70th birthday, the physicist said one of the greatest physics achievements of his career was the COBE satellite's discovery of small variations in the temperature of the cosmic microwave background radiation left over from the Big Bang.

Hawking believed that the future of the human species lay in space. He has repeatedly stated that humans will not survive if they remain only on Earth due to our invasive nature.

His unique life has repeatedly attracted the attention of documentarians and filmmakers, and in 2014, a biographical film about him, “Stephen Hawking Universe,” was made about him, starring Eddie Redmayne as Hawking. In addition, the scientist has appeared in several television shows, including The Simpsons, Red Dwarf and The Big Bang Theory.
At the premiere of the biographical film "Stephen Hawking's Universe"

In addition to his scientific work, Hawking was also known for his visionary statements. Here are some of them:

My goal is simple. It is a complete understanding of the universe, why it is the way it is, and why it exists at all.
In my opinion, the brain is a computer that stops working when its components fail. There is no heaven or afterlife for broken computers; This is a fairy tale story for people who are afraid of the dark.
I think the simplest explanation is that there is no God. No one created the Universe, and no one controls our destiny. This brings me to the profound realization that there is probably no heaven or afterlife. We have one lifetime to appreciate the grand design of the universe, and for that I am extremely grateful.
Remember to look at the stars and not at your feet.
Life would be tragic if it weren't funny.
My expectations were reduced to zero when I was 21 years old. Everything from then on was a bonus.
People who brag about their intelligence are losers.
We are just a progressive species of apes on a small planet of a very small star. But we can understand the universe. It turns us into something special.

Tags: ,

Stephen Hawking

BRIEF HISTORY OF TIME.

From the big bang to black holes

Acknowledgments

The book is dedicated to Jane

Apart from the fact that I fell ill with amyotrophic lateral sclerosis, then in almost everything else I was lucky. The help and support provided by my wife Jane and children Robert, Lucy and Timothy enabled me to lead a fairly normal life and achieve success at work. I was also lucky in that I chose theoretical physics, because it all fits in my head. Therefore, my physical weakness did not become a serious disadvantage. My scientific colleagues, without exception, always provided me with maximum assistance.

I am grateful to many who have read early versions of the book for suggestions on how it could be improved. Thus, Peter Gazzardi, my editor at Bantam Books, sent me letter after letter with comments and questions on passages that he felt were poorly explained. Admittedly, I was quite annoyed when I received a huge list of recommended fixes, but Gazzardi was absolutely right. I'm sure the book was made better by Gazzardi rubbing my nose in the mistakes.

I express my deep gratitude to my assistants Colin Williams, David Thomas and Raymond Laflamme, my secretaries Judy Fella, Ann Ralph, Cheryl Billington and Sue Macy and my nurses. I could not have achieved anything if all the costs of scientific research and necessary medical care had not been borne by Gonville and Caius College, the Science and Technology Research Council and the Leverhulme, MacArthur, Nuffield and Ralph Smith Foundations. I am very grateful to all of them.

Preface

We live, understanding almost nothing about the structure of the world. We don’t think about what mechanism generates the sunlight that ensures our existence, we don’t think about gravity, which keeps us on Earth, preventing it from throwing us into space. We are not interested in the atoms from which we are composed and on the stability of which we ourselves essentially depend. With the exception of children (who still know too little not to ask such serious questions), few people puzzle over why nature is the way it is, where the cosmos came from, and whether it has always existed? Couldn't time one day be turned back so that the effect precedes the cause? Is there an insurmountable limit to human knowledge? There are even children (I have met them) who want to know what a black hole looks like, what is the smallest particle of matter? why do we remember the past and not the future? If there really was chaos before, then how is it that apparent order has now been established? and why does the Universe exist at all?

In our society, it is common for parents and teachers to respond to these questions by mostly shrugging their shoulders or calling for help from vaguely remembered references to religious legends. Some people do not like such topics because they vividly reveal the narrowness of human understanding.

But the development of philosophy and the natural sciences moved forward mainly thanks to questions like these. More and more adults are showing interest in them, and the answers are sometimes completely unexpected for them. Differing in scale from both atoms and stars, we are pushing the horizons of exploration to cover both the very small and the very large.

In the spring of 1974, about two years before the Viking spacecraft reached the surface of Mars, I was in England at a conference organized by the Royal Society of London on the possibilities of searching for extraterrestrial civilizations. During a coffee break, I noticed a much larger meeting taking place in the next room and, out of curiosity, entered it. So I witnessed a long-standing ritual - the admission of new members to the Royal Society, which is one of the oldest associations of scientists on the planet. Ahead, a young man sitting in a wheelchair was very slowly writing his name in a book, the previous pages of which bore the signature of Isaac Newton. When he finally finished signing, the audience burst into applause. Stephen Hawking was already a legend then.

Hawking now occupies the chair of mathematics at the University of Cambridge, which was once occupied by Newton and later by P. A. M. Dirac - two famous researchers who studied one - the largest, and the other - the smallest. Hawking is their worthy successor. This first popular book by Hokippa contains a lot of useful things for a wide audience. The book is interesting not only for the breadth of its content, it allows you to see how the author’s thought works. You will find in it clear revelations about the limits of physics, astronomy, cosmology and courage.

But this is also a book about God... or maybe about the absence of God. The word "God" appears frequently in its pages. Hawking sets out to find the answer to Einstein's famous question about whether God had any choice when he created the Universe. Hawking is trying, as he himself writes, to unravel God's plan. All the more unexpected is the conclusion (at least temporary) to which these