The book "Eternity. In search of the ultimate theory of time "
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What is time in the modern sense and why does it have exactly such properties? Why does time always move in one direction? Why are there irreversible processes? Twenty years ago, Stephen Hawking tried to explain time through the Big Bang theory. Now Sean Carroll, one of the leading theoretical physicists of our time, will introduce you to the delightful paradigm of the theory of the arrow of time, which covers subjects from the entropy of quantum mechanics to time travel in information theory and the meaning of life.
The book "Eternity. Searching for the ultimate theory of time is not just the next step towards understanding why the Universe exists - this is an excellent reading for a wide range of readers who are interested in the physics and structure of our world.
')
This book is about the nature of time, about the origin of the Universe and about the fundamental structure of physical reality. We do not think here in any small, insignificant categories. We consider age-old, solid problems. Where did time and space come from? Is everything really limited to the Universe that we see, or are there other “Universes” beyond the limits of our gaze? How does the future differ from the past?
According to the authors of the Oxford Dictionary, time is the most frequently used noun in English. Throughout our lives, we move through time, follow it obsessively and try to overtake it every day, and yet, surprisingly, there are few people who can explain in simple words what time is.
We live in the Internet era, so it would be logical to turn for help to the free encyclopedia Wikipedia. At the time of this writing, the Time article begins with the following words:
Time is a component of the measuring system used to determine the order of events, to compare the duration of events and the intervals between them, as well as to quantitatively describe the movement of objects. Time is one of the main themes of religious, philosophical, and scientific research, but even the greatest scholars cannot give a definition of time in a consistent form applicable to all areas of research.
Let's go. By the end of the book, we will be able to formulate a very precise definition of time that will be applicable to all areas. Unfortunately, it is much less obvious why time has the properties it possesses, although we will nevertheless study a few intriguing ideas.
Cosmology, the teaching about the whole Universe, has greatly advanced over the last hundred years. Fourteen billion years ago, our Universe (or at least that part of it that we are able to observe) was in an unimaginably hot, dense state, which we call the Big Bang. Since then, the Universe is expanding and cooling, and, apparently, it will continue to do so in the foreseeable future, and maybe throughout eternity.
A hundred years ago, none of this was known to us - scientists had practically no idea about the structure of the Universe outside the Milky Way galaxy. Today, when we managed to take measurements of the observable Universe, we are able to describe in detail not only its size and shape, but also its constituent parts and the approximate course of history. However, we are not yet able to answer many important questions, in particular, related to the first moments of the Big Bang. As we learn, these questions play a critical role in our understanding of time - not only in the vast expanses of space, but also in our laboratories on Earth and even in our daily life.
Obviously, over time, the Universe evolves: the early Universe was hot and dense, the modern Universe is cold and sparse. But I'm going to outline a much deeper connection. The most mysterious characteristic of time is its orientation: the past is different from the future. This is the arrow of time. Unlike directions in space, which are equal among themselves, the Universe undoubtedly has a preferred orientation in time. The main theme of this book is that the arrow of time exists, because the Universe evolves in a certain way.
The reason why time has a direction is that the Universe is full of irreversible processes - events that occur in one direction of time, but never in the other. You can turn an egg into an omelet, as in the classic example, but it is impossible to make a whole egg out of an omelet. Milk mixes with coffee; fuel burns and turns into exhaust gases; people are born, grow up and die. In Nature, we everywhere find sequences of events in which one type of events always precedes the other, and another always follows. Together they define the arrow of time.
It is noteworthy that at the heart of all our understanding of irreversible processes lies a single concept - what is called entropy and measures the “disorder” of an object or a cluster of objects. Over time, entropy stubbornly increases, or at least remains constant - this is the famous second law of thermodynamics. 2 And the reason why entropy tends to increase is deceptively simple: there are many more ways to make a mess than to organize order; hence (ceteris paribus), ordered configurations will naturally flow into more and more erratic. It is not at all difficult to mix egg molecules in order to get an omelet, but to carefully assemble them back, forming a whole egg, is beyond our power.
This is where the traditional story that physicists usually tell about themselves ends. But there is another ingredient of incredible importance that has not received proper attention so far: if everything in the Universe evolves in the direction of increasing disorder, then it should start with an incredibly ordered configuration. This whole logical chain, explaining why it is impossible to turn an omelet into an egg, is obviously based on the fundamental assumption concerning the early Universe: it was in a state of very low entropy and very high orderliness.
The arrow of time connects the early Universe with what we literally experience at every moment of our life. This is not only breaking eggs and other irreversible processes, such as adding milk to coffee or cluttering up a room in which no one is cleaning up. The arrow of time is the reason why it seems to us that time passes by us or (if you like) why we are sailing through time. This is the reason why we remember the past, but not the future. Why we grow and change, why we have a metabolic process and why we eventually die. Why we believe in a causal relationship. This is a fundamental component of our idea of ​​free will.
And all this thanks to the Big Bang.
The mystery of the arrow of time, in essence, is the following: why the conditions in the early Universe were exactly as they were; why there was a configuration with low entropy, which allowed all these interesting and irreversible processes to occur? This book is dedicated to the research of this issue. Unfortunately, no one yet knows the correct answer to it. But in the development of modern science we have reached the stage at which we already have the necessary tools to seriously tackle this mystery.
Both scientists and ancient thinkers have always tried to understand time. In ancient Greece, the philosophers of the pre-Socratic times Heraclitus and Parmenides occupied different positions on the nature of time: Heraclitus emphasized the primacy of change, while Parmenides denied the reality of change in general. The nineteenth century was the heroic era of statistical mechanics: people learned to establish the behavior of macroscopic objects based on their microscopic components - when figures such as Ludwig Boltzmann, James Clerk Maxwell and Josiah Willard Gibbs managed to define entropy and describe its role in irreversible processes . However, they did not know anything about Einstein’s general theory of relativity or about quantum mechanics and, of course, about modern cosmology. For the first time in the history of science, we at least have a chance to assemble a sound theory of time and the evolution of the Universe.
I'm going to suggest the following version: The Big Bang was not the beginning of the universe. Cosmologists sometimes say that the Big Bang represents the true boundary of space and time, before which nothing existed - in fact, even time itself did not exist, therefore the concept of “before”, strictly speaking, cannot be used in this case. However, we know too little about the final laws of physics to make such statements with confidence. Scientists are increasingly beginning to appeal to the possibility that the Big Bang was not really the beginning of everything - this is just the phase through which the universe passes, or at least our part of the universe. If this is true, then the question of our low-entropic origin takes another form: not “Why did the universe originate in such a low-entropy state?”, But “Why did our part of the universe go through a period of such low entropy?”
Although this question does not seem simpler, it is another question, and it opens up a new range of possible answers. It is possible that the Universe that we see is just a part of a much larger Multiverse, which does not originate in a low-entropic configuration. I will argue that the most intelligent model of the Multipurpose is one where the entropy increases simply because the entropy can always increase: there is no state of maximum entropy. As an additional bonus, the Multipurpose can be completely symmetrical in time: starting from some point in the middle, when entropy has a high value, it evolves towards the past and future into states in which entropy is even higher. The universe available to our gaze is just a tiny process of an incredibly massive ensemble, and our particular journey from the dense Big Bang to the eternal void is part of the more global ambition of the Multiverse to increase its own entropy.
In any case, this is just one of the possibilities. Consider this as an example of one of the scenarios that cosmologists should consider if they decide to seriously tackle the problems posed by the arrow of time. And regardless of whether this particular idea leads us in the right direction, these problems themselves are already incredibly exciting and real. Throughout this book, we will study the problems of time from various points of view: time travel, information, quantum mechanics, the nature of eternity. When there is no certainty as to how the final answer should sound, the question should be tried to be asked in every way possible.
Not everyone agrees that cosmology should play a significant role in our understanding of the arrow of time. Once I had the opportunity to hold a seminar on this topic in a large audience at the physics department of a large educational institution. One of the older professors of this faculty considered my presentation insufficiently convincing and made efforts so that all those present would know about his displeasure. The next day, he sent an e-mail to other faculty members and was kind enough to include me in the mailing list:
Finally, the entropy value of the Universe as a function of time is an interesting problem for cosmology, but to assume that the laws of physics depend on it is utter nonsense. Carroll’s statement that the second law of thermodynamics owes its existence to cosmology is one of the silliest [sic] statements that I have heard at physical seminars, with the exception of the statement [surname] about consciousness in quantum mechanics. I am surprised that the physicists present kindly listened to such nonsense. Later, I had a dinner with several graduate students who readily supported my objections, but Carroll remained unmoved.
I hope he reads this book. There are many loud statements here, but I will be cautious, dividing them into three types: 1) the remarkable results of modern physics, which sound surprisingly, but nevertheless are generally accepted facts; 2) large-scale statements with which not all working physicists agree, but which nevertheless must be accepted, since their truth does not raise any questions; 3) speculative ideas outside the comfort zone of the current state of affairs in science. Definitely, we will not shy away from abstract and speculative reasoning, but they will always be clearly marked as such. Ultimately, you will be armed with all the necessary knowledge to decide for yourself which parts of the story make sense and which parts do not.
The topic of time includes a huge number of ideas - from household to shocking. We will look into thermodynamics, quantum mechanics, special and general relativity, information theory, cosmology, elementary particle physics, and quantum gravity. The first part of the book can be viewed as a sightseeing tour, telling about entropy and the arrow of time, the evolution of the Universe and various concepts of the very idea of ​​"time". After that, we will try to approach the issue more systematically: in the second part, we will think deeply about space — time and relativity, including the possibility of traveling back in time. In the third part, we will seriously consider the concept of entropy, examining its role in a variety of contexts, from the evolution of life to the mysteries of quantum mechanics.
In the fourth part we will put everything together in order to boldly look into the eyes of the riddles that entropy confronts modern cosmologists: how the Universe should look and how similar is it to how the Universe actually looks? I will demonstrate that the Universe does not look like it should “(of course, explaining what I mean by using this word), at least this is the case for the Universe that we see around us. If our Universe originated in the Big Bang, its existence is aggravated by a finely tuned boundary condition for which we cannot find a worthy explanation. However, if the observable Universe is part of a larger ensemble - the Multi-Loop, then perhaps we have a chance to explain why in a tiny part of this ensemble, entropy at one end of time is so drastically different from entropy at the other.
All this, of course, is an unforgivable theorizing, but these fabrications should be taken seriously. The stakes are great - time, space, the Universe, so the mistakes that we will certainly make along the way, without a doubt, will also differ in scale. Sometimes it is useful to let your imagination float freely, even if our ultimate goal is to return to Earth and explain what is happening in the kitchen.
More information about the book can be found on the publisher's website.
Table of contents
Excerpt
For readers of this blog 25% discount coupon - Eternity
What is time in the modern sense and why does it have exactly such properties? Why does time always move in one direction? Why are there irreversible processes? Twenty years ago, Stephen Hawking tried to explain time through the Big Bang theory. Now Sean Carroll, one of the leading theoretical physicists of our time, will introduce you to the delightful paradigm of the theory of the arrow of time, which covers subjects from the entropy of quantum mechanics to time travel in information theory and the meaning of life.The book "Eternity. Searching for the ultimate theory of time is not just the next step towards understanding why the Universe exists - this is an excellent reading for a wide range of readers who are interested in the physics and structure of our world.
')
This book is about the nature of time, about the origin of the Universe and about the fundamental structure of physical reality. We do not think here in any small, insignificant categories. We consider age-old, solid problems. Where did time and space come from? Is everything really limited to the Universe that we see, or are there other “Universes” beyond the limits of our gaze? How does the future differ from the past?
According to the authors of the Oxford Dictionary, time is the most frequently used noun in English. Throughout our lives, we move through time, follow it obsessively and try to overtake it every day, and yet, surprisingly, there are few people who can explain in simple words what time is.
We live in the Internet era, so it would be logical to turn for help to the free encyclopedia Wikipedia. At the time of this writing, the Time article begins with the following words:
Time is a component of the measuring system used to determine the order of events, to compare the duration of events and the intervals between them, as well as to quantitatively describe the movement of objects. Time is one of the main themes of religious, philosophical, and scientific research, but even the greatest scholars cannot give a definition of time in a consistent form applicable to all areas of research.
Let's go. By the end of the book, we will be able to formulate a very precise definition of time that will be applicable to all areas. Unfortunately, it is much less obvious why time has the properties it possesses, although we will nevertheless study a few intriguing ideas.
Cosmology, the teaching about the whole Universe, has greatly advanced over the last hundred years. Fourteen billion years ago, our Universe (or at least that part of it that we are able to observe) was in an unimaginably hot, dense state, which we call the Big Bang. Since then, the Universe is expanding and cooling, and, apparently, it will continue to do so in the foreseeable future, and maybe throughout eternity.
A hundred years ago, none of this was known to us - scientists had practically no idea about the structure of the Universe outside the Milky Way galaxy. Today, when we managed to take measurements of the observable Universe, we are able to describe in detail not only its size and shape, but also its constituent parts and the approximate course of history. However, we are not yet able to answer many important questions, in particular, related to the first moments of the Big Bang. As we learn, these questions play a critical role in our understanding of time - not only in the vast expanses of space, but also in our laboratories on Earth and even in our daily life.
Time after big bang
Obviously, over time, the Universe evolves: the early Universe was hot and dense, the modern Universe is cold and sparse. But I'm going to outline a much deeper connection. The most mysterious characteristic of time is its orientation: the past is different from the future. This is the arrow of time. Unlike directions in space, which are equal among themselves, the Universe undoubtedly has a preferred orientation in time. The main theme of this book is that the arrow of time exists, because the Universe evolves in a certain way.
The reason why time has a direction is that the Universe is full of irreversible processes - events that occur in one direction of time, but never in the other. You can turn an egg into an omelet, as in the classic example, but it is impossible to make a whole egg out of an omelet. Milk mixes with coffee; fuel burns and turns into exhaust gases; people are born, grow up and die. In Nature, we everywhere find sequences of events in which one type of events always precedes the other, and another always follows. Together they define the arrow of time.
It is noteworthy that at the heart of all our understanding of irreversible processes lies a single concept - what is called entropy and measures the “disorder” of an object or a cluster of objects. Over time, entropy stubbornly increases, or at least remains constant - this is the famous second law of thermodynamics. 2 And the reason why entropy tends to increase is deceptively simple: there are many more ways to make a mess than to organize order; hence (ceteris paribus), ordered configurations will naturally flow into more and more erratic. It is not at all difficult to mix egg molecules in order to get an omelet, but to carefully assemble them back, forming a whole egg, is beyond our power.
This is where the traditional story that physicists usually tell about themselves ends. But there is another ingredient of incredible importance that has not received proper attention so far: if everything in the Universe evolves in the direction of increasing disorder, then it should start with an incredibly ordered configuration. This whole logical chain, explaining why it is impossible to turn an omelet into an egg, is obviously based on the fundamental assumption concerning the early Universe: it was in a state of very low entropy and very high orderliness.
The arrow of time connects the early Universe with what we literally experience at every moment of our life. This is not only breaking eggs and other irreversible processes, such as adding milk to coffee or cluttering up a room in which no one is cleaning up. The arrow of time is the reason why it seems to us that time passes by us or (if you like) why we are sailing through time. This is the reason why we remember the past, but not the future. Why we grow and change, why we have a metabolic process and why we eventually die. Why we believe in a causal relationship. This is a fundamental component of our idea of ​​free will.
And all this thanks to the Big Bang.
We see not all
The mystery of the arrow of time, in essence, is the following: why the conditions in the early Universe were exactly as they were; why there was a configuration with low entropy, which allowed all these interesting and irreversible processes to occur? This book is dedicated to the research of this issue. Unfortunately, no one yet knows the correct answer to it. But in the development of modern science we have reached the stage at which we already have the necessary tools to seriously tackle this mystery.
Both scientists and ancient thinkers have always tried to understand time. In ancient Greece, the philosophers of the pre-Socratic times Heraclitus and Parmenides occupied different positions on the nature of time: Heraclitus emphasized the primacy of change, while Parmenides denied the reality of change in general. The nineteenth century was the heroic era of statistical mechanics: people learned to establish the behavior of macroscopic objects based on their microscopic components - when figures such as Ludwig Boltzmann, James Clerk Maxwell and Josiah Willard Gibbs managed to define entropy and describe its role in irreversible processes . However, they did not know anything about Einstein’s general theory of relativity or about quantum mechanics and, of course, about modern cosmology. For the first time in the history of science, we at least have a chance to assemble a sound theory of time and the evolution of the Universe.
I'm going to suggest the following version: The Big Bang was not the beginning of the universe. Cosmologists sometimes say that the Big Bang represents the true boundary of space and time, before which nothing existed - in fact, even time itself did not exist, therefore the concept of “before”, strictly speaking, cannot be used in this case. However, we know too little about the final laws of physics to make such statements with confidence. Scientists are increasingly beginning to appeal to the possibility that the Big Bang was not really the beginning of everything - this is just the phase through which the universe passes, or at least our part of the universe. If this is true, then the question of our low-entropic origin takes another form: not “Why did the universe originate in such a low-entropy state?”, But “Why did our part of the universe go through a period of such low entropy?”
Although this question does not seem simpler, it is another question, and it opens up a new range of possible answers. It is possible that the Universe that we see is just a part of a much larger Multiverse, which does not originate in a low-entropic configuration. I will argue that the most intelligent model of the Multipurpose is one where the entropy increases simply because the entropy can always increase: there is no state of maximum entropy. As an additional bonus, the Multipurpose can be completely symmetrical in time: starting from some point in the middle, when entropy has a high value, it evolves towards the past and future into states in which entropy is even higher. The universe available to our gaze is just a tiny process of an incredibly massive ensemble, and our particular journey from the dense Big Bang to the eternal void is part of the more global ambition of the Multiverse to increase its own entropy.
In any case, this is just one of the possibilities. Consider this as an example of one of the scenarios that cosmologists should consider if they decide to seriously tackle the problems posed by the arrow of time. And regardless of whether this particular idea leads us in the right direction, these problems themselves are already incredibly exciting and real. Throughout this book, we will study the problems of time from various points of view: time travel, information, quantum mechanics, the nature of eternity. When there is no certainty as to how the final answer should sound, the question should be tried to be asked in every way possible.
There will always be skeptics
Not everyone agrees that cosmology should play a significant role in our understanding of the arrow of time. Once I had the opportunity to hold a seminar on this topic in a large audience at the physics department of a large educational institution. One of the older professors of this faculty considered my presentation insufficiently convincing and made efforts so that all those present would know about his displeasure. The next day, he sent an e-mail to other faculty members and was kind enough to include me in the mailing list:
Finally, the entropy value of the Universe as a function of time is an interesting problem for cosmology, but to assume that the laws of physics depend on it is utter nonsense. Carroll’s statement that the second law of thermodynamics owes its existence to cosmology is one of the silliest [sic] statements that I have heard at physical seminars, with the exception of the statement [surname] about consciousness in quantum mechanics. I am surprised that the physicists present kindly listened to such nonsense. Later, I had a dinner with several graduate students who readily supported my objections, but Carroll remained unmoved.
I hope he reads this book. There are many loud statements here, but I will be cautious, dividing them into three types: 1) the remarkable results of modern physics, which sound surprisingly, but nevertheless are generally accepted facts; 2) large-scale statements with which not all working physicists agree, but which nevertheless must be accepted, since their truth does not raise any questions; 3) speculative ideas outside the comfort zone of the current state of affairs in science. Definitely, we will not shy away from abstract and speculative reasoning, but they will always be clearly marked as such. Ultimately, you will be armed with all the necessary knowledge to decide for yourself which parts of the story make sense and which parts do not.
The topic of time includes a huge number of ideas - from household to shocking. We will look into thermodynamics, quantum mechanics, special and general relativity, information theory, cosmology, elementary particle physics, and quantum gravity. The first part of the book can be viewed as a sightseeing tour, telling about entropy and the arrow of time, the evolution of the Universe and various concepts of the very idea of ​​"time". After that, we will try to approach the issue more systematically: in the second part, we will think deeply about space — time and relativity, including the possibility of traveling back in time. In the third part, we will seriously consider the concept of entropy, examining its role in a variety of contexts, from the evolution of life to the mysteries of quantum mechanics.
In the fourth part we will put everything together in order to boldly look into the eyes of the riddles that entropy confronts modern cosmologists: how the Universe should look and how similar is it to how the Universe actually looks? I will demonstrate that the Universe does not look like it should “(of course, explaining what I mean by using this word), at least this is the case for the Universe that we see around us. If our Universe originated in the Big Bang, its existence is aggravated by a finely tuned boundary condition for which we cannot find a worthy explanation. However, if the observable Universe is part of a larger ensemble - the Multi-Loop, then perhaps we have a chance to explain why in a tiny part of this ensemble, entropy at one end of time is so drastically different from entropy at the other.
All this, of course, is an unforgivable theorizing, but these fabrications should be taken seriously. The stakes are great - time, space, the Universe, so the mistakes that we will certainly make along the way, without a doubt, will also differ in scale. Sometimes it is useful to let your imagination float freely, even if our ultimate goal is to return to Earth and explain what is happening in the kitchen.
More information about the book can be found on the publisher's website.
Table of contents
Excerpt
For readers of this blog 25% discount coupon - Eternity
Source: https://habr.com/ru/post/367981/
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