What do you think?
Rate this book
The Edge of Knowledge: Unsolved Mysteries of the Cosmos
Lawrence Krauss explores the greatest unanswered questions at the forefront of science today, and likely for the coming century and beyond.
Internationally known theoretical physicist and bestselling author Lawrence Krauss explores science’s greatest unanswered questions.
Three of the most important words in science are “I don't know.” Not knowing implies a Universe of opportunities—the possibility of discovery and surprise. Our understanding of science has advanced immeasurably over the last five hundred years, yet many fundamental mysteries of existence How did our Universe begin? How big is the Universe? Is time travel possible? What’s at the center of a black hole? How did life on Earth arise? Are we alone? What is consciousness, and can we create it?
These mysteries define the scientific forefront—the threshold of the unknown. To explore that threshold is to gain a deeper understanding of just how far science has progressed. Covering time, space, matter, life, and consciousness, Krauss introduces readers to topics that will shape the state of science for the next century, providing us all passport to our own journeys of exploration and discovery.
Internationally known theoretical physicist and bestselling author Lawrence Krauss explores science’s greatest unanswered questions.
Three of the most important words in science are “I don't know.” Not knowing implies a Universe of opportunities—the possibility of discovery and surprise. Our understanding of science has advanced immeasurably over the last five hundred years, yet many fundamental mysteries of existence How did our Universe begin? How big is the Universe? Is time travel possible? What’s at the center of a black hole? How did life on Earth arise? Are we alone? What is consciousness, and can we create it?
These mysteries define the scientific forefront—the threshold of the unknown. To explore that threshold is to gain a deeper understanding of just how far science has progressed. Covering time, space, matter, life, and consciousness, Krauss introduces readers to topics that will shape the state of science for the next century, providing us all passport to our own journeys of exploration and discovery.
240 pages, Hardcover
First published May 9, 2023
About the author
Lawrence M. Krauss
36 books1,731 followersLawrence Maxwell Krauss is a Canadian-American theoretical physicist and cosmologist who taught at Arizona State University (ASU), Yale University, and Case Western Reserve University. He founded ASU's Origins Project in 2008 to investigate fundamental questions about the universe and served as the project's director.
Krauss is an advocate for public understanding of science, public policy based on sound empirical data, scientific skepticism, and science education. An anti-theist, Krauss seeks to reduce the influence of what he regards as superstition and religious dogma in popular culture. Krauss is the author of several bestselling books, including The Physics of Star Trek (1995) and A Universe from Nothing (2012), and chaired the Bulletin of the Atomic Scientists Board of Sponsors.
Upon investigating allegations about sexual misconduct by Krauss, ASU determined that Krauss had violated university policy, and did not renew his Origins Project directorship for a third term in July 2018. Krauss retired as a professor at ASU in May 2019, at the end of the following academic year. He currently serves as president of The Origins Project Foundation. Krauss hosts The Origins Podcast with Lawrence Krauss and publishes a blog titled Critical Mass.
Krauss is an advocate for public understanding of science, public policy based on sound empirical data, scientific skepticism, and science education. An anti-theist, Krauss seeks to reduce the influence of what he regards as superstition and religious dogma in popular culture. Krauss is the author of several bestselling books, including The Physics of Star Trek (1995) and A Universe from Nothing (2012), and chaired the Bulletin of the Atomic Scientists Board of Sponsors.
Upon investigating allegations about sexual misconduct by Krauss, ASU determined that Krauss had violated university policy, and did not renew his Origins Project directorship for a third term in July 2018. Krauss retired as a professor at ASU in May 2019, at the end of the following academic year. He currently serves as president of The Origins Project Foundation. Krauss hosts The Origins Podcast with Lawrence Krauss and publishes a blog titled Critical Mass.
Ratings & Reviews
Friends & Following
Create a free account to discover what your friends think of this book!
Community Reviews
Displaying 1 - 30 of 35 reviews
August 2, 2023
“The Edge of Knowledge: Unsolved Mysteries of the Cosmos” is a fascinating and enlightening book that explores some of the most profound questions that science has yet to answer. The author, Lawrence M Krauss, is a renowned theoretical physicist and a popular science writer who has written several best-selling books on topics such as the origin and fate of the universe, the nature of matter and energy, and the physics of Star Trek.
In this book, Krauss takes us on a journey through the frontiers of science, where we encounter the limits of our knowledge and the possibilities of discovery. He divides the book into five chapters, each focusing on a different area of mystery: time, space, matter, life, and consciousness. In each chapter, he explains the current state of scientific understanding, the challenges and paradoxes that remain unsolved, and the potential implications for our worldview and our future.
Krauss writes with clarity, humor, and passion, making complex concepts accessible and engaging for a general audience. He also shares his personal insights and experiences as a scientist, revealing his curiosity, wonder, and skepticism. He does not shy away from admitting what he does not know or what he finds puzzling or controversial. He invites us to join him in his quest for knowledge and to appreciate the beauty and mystery of nature.
The Edge of Knowledge is not only a book about science, but also a book about philosophy, culture, and history. Krauss shows how science is influenced by and influences our human endeavors and values. He discusses how science relates to religion, art, literature, politics, and ethics. He also traces the historical development of scientific ideas and discoveries, highlighting the achievements and challenges of some of the greatest scientists in history.
The interview with Krauss at the end of the book, where he answers commonly asked questions, is also a nice touch.
The Edge of Knowledge is a book that will inspire you to think deeply about the world around you and within you. It will challenge you to question your assumptions and to expand your horizons. It will also remind you that science is not a collection of facts, but a process of exploration and discovery that never ends. As Krauss writes in the introduction: "The edge of knowledge is where we are most alive."
In this book, Krauss takes us on a journey through the frontiers of science, where we encounter the limits of our knowledge and the possibilities of discovery. He divides the book into five chapters, each focusing on a different area of mystery: time, space, matter, life, and consciousness. In each chapter, he explains the current state of scientific understanding, the challenges and paradoxes that remain unsolved, and the potential implications for our worldview and our future.
Krauss writes with clarity, humor, and passion, making complex concepts accessible and engaging for a general audience. He also shares his personal insights and experiences as a scientist, revealing his curiosity, wonder, and skepticism. He does not shy away from admitting what he does not know or what he finds puzzling or controversial. He invites us to join him in his quest for knowledge and to appreciate the beauty and mystery of nature.
The Edge of Knowledge is not only a book about science, but also a book about philosophy, culture, and history. Krauss shows how science is influenced by and influences our human endeavors and values. He discusses how science relates to religion, art, literature, politics, and ethics. He also traces the historical development of scientific ideas and discoveries, highlighting the achievements and challenges of some of the greatest scientists in history.
The interview with Krauss at the end of the book, where he answers commonly asked questions, is also a nice touch.
The Edge of Knowledge is a book that will inspire you to think deeply about the world around you and within you. It will challenge you to question your assumptions and to expand your horizons. It will also remind you that science is not a collection of facts, but a process of exploration and discovery that never ends. As Krauss writes in the introduction: "The edge of knowledge is where we are most alive."
June 11, 2023
I am a fan of Krauss and enjoyed and learned a lot from "A Universe from Nothing" and "The Physics of Climate Change". Those books spend considerable time laying the groundwork for the explanations that follow. The first three chapters of this book however go deep without first laying a foundation. I found myself constantly referring to Wikipedia and still being confused. These areas are his specialty and he has a lot of knowledge to impart but without a proper introduction they are lost on the intended audience. The last two chapters are a quick read and more like a survey or report on some of the current thinking but without any depth. The books he references are much more informative and provide more background and support for the models they put forth.
In my opinion Krauss should have written 3 books, one for each of the first three chapters, laying out the background necessary for understanding the material and conclusions he presents in the style of his other books. Trying to explain the current depth of knowledge in all these areas in a short book is a mistake.
In my opinion Krauss should have written 3 books, one for each of the first three chapters, laying out the background necessary for understanding the material and conclusions he presents in the style of his other books. Trying to explain the current depth of knowledge in all these areas in a short book is a mistake.
September 11, 2023
It is remarkable how well you can enjoy reading a book, whilst largely understanding absolutely diddy squat as to what is being talked about. This book is yet another reminder to myself of my scientific illiteracy, and I need a more dumbed down version to get the gist, at least in relation to the astrophysics chat, the latter questions of life and consciousness I can follow with a bit more ease, without getting lost amidst all the quarks and the muons and spin particles and the like. None of which is the fault of the author by any means, who writes well, and perfectly reasonably enough expects people who are reading this book, even the lay-readers to have a still functioning memory of at least school-level physics, which sadly rules me out for some of the sections of the book. But nevertheless despite that, I was still able to appreciate to some extent the importance of certain milestones in discoveries, which is a credit to the author.
Throughout, it is an engaging work and the passion for exploring the unknowns and working with the mysteries of the universe are clearly as spell-binding to the author now as they have ever been and that enthusiasm shines through clearly, and for those with the capacities to handle maths and all that, I can imagine it is the type of book that will inspire new generations of young scientists to get to work on these big ideas.
Me, I'll just wait for the next big colourful documentary, that paints in brilliantly broad strokes.
Throughout, it is an engaging work and the passion for exploring the unknowns and working with the mysteries of the universe are clearly as spell-binding to the author now as they have ever been and that enthusiasm shines through clearly, and for those with the capacities to handle maths and all that, I can imagine it is the type of book that will inspire new generations of young scientists to get to work on these big ideas.
Me, I'll just wait for the next big colourful documentary, that paints in brilliantly broad strokes.
September 22, 2024
While I have great respect for Lawrence Krauss, I found this book less engaging than anticipated and often felt confused. 😔 Although giving it 2 stars may not fully do the book justice, it accurately reflects my personal experience and level of enjoyment. In contrast, ''A Universe from Nothing'' is written with much greater clarity, and I found its concepts easier to grasp.
April 19, 2024
The Edge of Knowledge: Unsolved Mysteries of the Cosmos is a super interesting science book in which theoretical physicist Lawrence Krauss takes a deep dive in to known unknowns in five different subjects: time, space, matter, life, and consciousness. He also reminds the reader that there may be unknown unknowns in science as well (and yes, he includes that Donald Rumsfeld quote in the opening pages). As much as we know about science there is much more yet to be discovered, more so in some subjects such as matter and space, than others such as life / biology. The beauty of science is recognizing we don't have all the answers, and it's fun to read about all the possibilities. It's much more fun to pursue knowledge than pretend you know that everything was created supernaturally and there is no need for questions.
I really liked this book and like Krauss's mostly non-overly technical style of writing. He starts out each chapter with several questions which he will address for each subject. I feel like I have a pretty solid basic understanding of most scientific concepts and was blown away by some of Krauss's hypothesizing but also overwhelmed as some of this went way over my head. Two concepts I struggle with are quantum theory and string theory and no matter how much I read about them I just can't wrap my primate brain around them.
The standout chapters for me were Time and Life. The concept of time and time travel have always been science fiction plot devices and have always piqued my interest. The Life chapter addressed questions: What is life?, How did life originate?, Is DNA life unique?, Are we alone?, and What is the future of life?. This chapter was fascinating to me, especially the science of the origin of life which Krauss predicts will be solved in the coming decades with all we've learned recently from science such as the amount of organic material traveling through space on asteroids and comets and the sheer amount of water we've discovered on other bodies in our solar systems and on comets in our solar neighborhood. Creationists, whose "god of the gaps" has been regulated to a minute space through scientific discoveries over the last couple of centuries, can give up the ghost once we show how life arrived on Earth naturally. Prevailing scientific theories have always been more feasible than their explanation: magic!
The book contains an impressively through index in which every scientific concept and player in the field is listed, Krauss leaves no stone unturned. The book is only around 200 pages and it a quick read. I highly recommend even though I didn't understand parts of it.
Personal anecdote: about a month ago I attended a Zoom presentation by Atheists For Liberty in which Lawrence M. Krauss was one of the featured speakers. It was fantastic. Krauss spoke from his office and I noticed that behind him he had a picture of the great 19th-century agnostic orator Robert G Ingersoll, a personal hero of mine. I commented in the busy chat that I also admired the great Ingersoll and liked his picture. After Krauss presented he jumped in the chat and thanked me for my comment, and stated that this was an original photograph of Ingersoll given to him by Johnny Depp! In this book Krauss mentions that he participated in a public dialogue with Johnny Depp on the subject of computers, creativity, and madness.
I really liked this book and like Krauss's mostly non-overly technical style of writing. He starts out each chapter with several questions which he will address for each subject. I feel like I have a pretty solid basic understanding of most scientific concepts and was blown away by some of Krauss's hypothesizing but also overwhelmed as some of this went way over my head. Two concepts I struggle with are quantum theory and string theory and no matter how much I read about them I just can't wrap my primate brain around them.
The standout chapters for me were Time and Life. The concept of time and time travel have always been science fiction plot devices and have always piqued my interest. The Life chapter addressed questions: What is life?, How did life originate?, Is DNA life unique?, Are we alone?, and What is the future of life?. This chapter was fascinating to me, especially the science of the origin of life which Krauss predicts will be solved in the coming decades with all we've learned recently from science such as the amount of organic material traveling through space on asteroids and comets and the sheer amount of water we've discovered on other bodies in our solar systems and on comets in our solar neighborhood. Creationists, whose "god of the gaps" has been regulated to a minute space through scientific discoveries over the last couple of centuries, can give up the ghost once we show how life arrived on Earth naturally. Prevailing scientific theories have always been more feasible than their explanation: magic!
The book contains an impressively through index in which every scientific concept and player in the field is listed, Krauss leaves no stone unturned. The book is only around 200 pages and it a quick read. I highly recommend even though I didn't understand parts of it.
Personal anecdote: about a month ago I attended a Zoom presentation by Atheists For Liberty in which Lawrence M. Krauss was one of the featured speakers. It was fantastic. Krauss spoke from his office and I noticed that behind him he had a picture of the great 19th-century agnostic orator Robert G Ingersoll, a personal hero of mine. I commented in the busy chat that I also admired the great Ingersoll and liked his picture. After Krauss presented he jumped in the chat and thanked me for my comment, and stated that this was an original photograph of Ingersoll given to him by Johnny Depp! In this book Krauss mentions that he participated in a public dialogue with Johnny Depp on the subject of computers, creativity, and madness.
October 30, 2023
Practically the only section where I felt I learned something new was the last one about consciousness. The rest was more or less the same information you would learn if you've read enough books or watched enough documentaries about physics, cosmology and the evolution of life. I guess humanity is nowhere near solving the mysteries posed by these three areas, and consciousness is only still a fascinating subject because its study is still in its very early infancy, and there are still many new widely varied ideas being thrown around as to its nature and relationship to brain processes, as well as interpretations of different experiments that have been conducted to elucidate it.
January 31, 2024
Review to come...
August 6, 2023
A HISTORICAL OVERVIEW OF MANY CHALLENGING QUESTIONS/ISSUES
Theoretical physicists Lawrence Krauss wrote in the Foreword to this 2023 book, “Three of the most important words in science are: ‘I don’t know.’ Therein lies the beginning of enlightenment, because not knowing implies… the possibility of discovery and of surprise. If history is any guide, there is a lot more about the universe that we don’t know than we do… The limits of the word we understand have moved further and further beyond the universe of our direct experience over the past five hundred years… Yet the fundamental mysteries of existence persist: How did our universe begin, if it even had a beginning? How will it end?... What are the fundamental laws governing our existence? Are those laws the same everywhere?... How did life on earth arise? Are we alone? What is consciousness? Is human consciousness unique?... The mysteries… define … the threshold of the unknown. To explore that threshold is to gai a deeper understanding of just how far science has progressed. That is the purpose of this book… It is structured around the big outstanding mysteries mentioned earlier…. The result, I hope, will be a celebration of knowledge rather than of ignorance. It is an invitation to ponder and appreciate the universe in which we live.” (Pg. xv-xvi)
He recounts, “As I described in ‘The Physics of Star Trek’… a stable wormhole… can always be turned into a time machine… The problem… is that wormholes cannot be stable if normal matter and energy are all we have available to create one. Each mouth of the wormhole will collapse to form a black hole out of which nothing can escape in a time shorter than it would take to traverse the wormhole. The only way to stabilize a wormhole is to fill it up with a new, exotic kind of energy… and there are persuasive arguments that one cannot create, even in principle, such energy in the laboratory… knowing how to untangle the precise relativistic quantum properties of curved spacetimes is required to resolve the issue, and we don’t yet have the technology to do so.” (Pg. 34)
He explains, “space and time… become relativistic quantum mechanical variables. And relativistic quantum variables can spontaneously be created and destroyed. Whole ‘virtual’ spacetimes, like our own universe, could spontaneously pop into existence. But… only those spacetimes that have zero total energy might be expected to survive more than an instant, much less 13.8 billion years, before disappearing.” (Pg. 45-46)
He suggests, “if there is a multiverse, there may be no such fundamental principles. Many of the basic characteristics of our universe might be accidental. It could be that the laws of physics could be quite different in each universe within the multiverse, and that we measure the laws we do because our universe happened to allow the formation of galaxies, planets and life… If an infinite number of universes are formed over an infinite time, then the laws of probability suggest it is inevitable that there will be other universes just like our own… and everything we now see would exist as an exact copy, with perhaps a few exceptions. In that universe, the copy of you might be writing this book now, and the copy of me might … be reading it, for example… Every possibility that could exist, would exist…” (Pg. 55-56)
He recounts, “Physicists trying to develop a quantum theory of gravity … discovered a theory in which the fundamental spacetime objects were... string-like objects… The theory would indeed allow general relativity to be consistently quantized, but only if spacetime had not four dimensions, but twenty-six. This was a lot to swallow… for many physicists… a large cadre of very talented theorists … discovered that… it was possible to reduce the number of dimensions from twenty-six down to ten or eleven…. [But] if there are indeed other dimensions in nature, where are they hiding?... These extra dimensions could be curled up into a very small six- or seven-dimensional ball… The diameter of the ball would be … about nineteen orders of magnitude smaller than the diameter of the nucleus of a hydrogen atom!... For this reason… string theory remains a fascinating area of study … but whether it has anything to do with the real world remains an open question.” (Pg. 59-60)
He acknowledges, “it is possible to … outline the various key features that underlie our quantum universe… These five facts capture most of the craziness of quantum theory. They imply that the sensible classical reality that most of us take for granted is an illusion… physicists from Einstein onward have argued that while the mathematics of quantum mechanics clearly provides correct predictions about how the world works… quantum mechanics is simply too crazy to be absolutely true.” (Pg. 113-116)
He clarifies, ‘In my book, ‘A Universe from Nothing,’ I argued that quantum creation of universes from nothing is to be expected, and that the properties of such a universe will… inevitably resemble the properties of the universe in which we live. But I acknowledged … that simply having no space, no time, no particles, and no radiation, may not be fully NOTHING What about the laws of physics? Did they antedate our universe?” (Pg. 121)
He argues, “Some individuals who refuse to accept the likelihood of the natural formation of life and demand a supernatural explanation point to … complexity as a proof of the inadequacy of natural mechanisms to explain life’s appearance… The problem with this viewpoint is that, just like evolution, the origin of life weas likely not a completely random process. The laws of chemistry depend on the subtle interplay between the physical concepts of entropy… and enthalpy…” (Pg. 128-129)
He cautions, “many of the planets within their star’s habitable zones exist much closer to their host stars than the earth does to the sun… Thus, every time another earth-like planet is reported in the press, it is best to remain skeptical about the possibilities of finding life on it.” (Pg. 146)
He states, “perhaps, as… some scientists… like to imagine, life was INTENTIONALLY seeded on this planet by an advanced civilization… this notion… merely puts off the origins of life issue. If life on earth evolved because it was jump-started by life elsewhere, what about the life elsewhere? Was it seeded too? Eventually the buck will have to stop, and the non-biological origin of life will have to be explained. For this reason, I don’t really take panspermia seriously.” (Pg. 150)
He observes, “in a universe that expands FOREVER, there may be local fluctuations that might, with unbelievably small but NON-ZERO probabilities, cause momentary (in a cosmic sense) emergences of some news life forms. They too will die out, but the process may reoccur every now and then, forever. In that vague and improbable sense, life itself might never end in the universe. It just won’t be the same life that survives…” (Pg. 160)
He asserts, “the universe isn’t fine-tuned for life. Rather, life on earth arose because it could. Just s in the case of biological evolution, life is fine-tuned for the universe, rather than the other way around. The existence of life in our universe seems miraculous, but it need not be a miracle. The mysteries surrounding the origin of life, its variety, and its possible future are fascinating and provocative. The fact that we don’t yet fully understand these things is not evidence for God or that we live in some vast video game created by some more advanced civilization … Rather, it is simply evidence of not understanding, and that motivates trying to find out the answers… Not only are we not likely to be special gifts of creation, but the possible existence of lifeforms with nothing in common with us lends further incredulity to the incredibly non-humble suggestion that the universe was made for us.” (Pg. 162)
He admits, “the phenomenon of consciousness is the one area I know of in science where the forefront discussions seem to be made by philosophers equally as often as they are made by experimental cognitive scientists. I tend to view this as an indication of a science in its early stages. Philosophy is indispensable for developing the questions in fields of science where it is not clear what the important questions are, namely, the ones that scientists will use later to explore nature, which in turn lead to further questions, answers, and so on.” (Pg. 166-167)
He notes, “I have never liked the term artificial intelligence as it applies to the technologies we are creating, because there is, as far as I can see, nothing artificial or intelligent about it. Most of what is now classified as AI is really a case of machine learning (ML). With ML, computers sift through mountains of data. Faced with increasing amounts of data, real and imagined, internet companies are under immediate pressure to help develop software and hardware that can ‘learn’ from the data---that is, systems that can adapt to future real-time data inputs, using information gleaned from scouring massive amounts of past data.” (Pg. 192)
He asks, “The key question…is whether such an evolutionary history is… necessary to recreate consciousness in machines. Will devices that do not have the hierarchical framework of our brains---with forebrain and midbrain built on hindbrain, with succeeding layers taking on new tasks while interfacing and communicating across the entire system, all the while being intimately tied to bodily sensory information flow and regulation---be able to achieve consciousness? Time will tell. It may be that fundamentally new computational devices, perhaps based on quantum computing ideas, will be required. I personally suspect, no matter how challenging, that there is no fundamental roadblock getting in the way of ultimately developing functioning self-aware machines.” (Pg. 196)
He concludes, “What is called artificial intelligence is a natural by-product of human development, just as writing was then. Technology, a human invention, changes the world, but it also requires humans to change with it. This has been going on long as humans have been human. An AI future may be better than the present. After all, I imagine most people today think a world of books to read is better than the world before writing allowed them to be written. Recognizing that we don’t know what the future will bring, just as recognizing how many questions about the universe are yet to be answered, may help us ensure that the future always remains more exciting than the past.” (Pg. 199)
This book will be of great interest to those concerned with current issues in science.
Theoretical physicists Lawrence Krauss wrote in the Foreword to this 2023 book, “Three of the most important words in science are: ‘I don’t know.’ Therein lies the beginning of enlightenment, because not knowing implies… the possibility of discovery and of surprise. If history is any guide, there is a lot more about the universe that we don’t know than we do… The limits of the word we understand have moved further and further beyond the universe of our direct experience over the past five hundred years… Yet the fundamental mysteries of existence persist: How did our universe begin, if it even had a beginning? How will it end?... What are the fundamental laws governing our existence? Are those laws the same everywhere?... How did life on earth arise? Are we alone? What is consciousness? Is human consciousness unique?... The mysteries… define … the threshold of the unknown. To explore that threshold is to gai a deeper understanding of just how far science has progressed. That is the purpose of this book… It is structured around the big outstanding mysteries mentioned earlier…. The result, I hope, will be a celebration of knowledge rather than of ignorance. It is an invitation to ponder and appreciate the universe in which we live.” (Pg. xv-xvi)
He recounts, “As I described in ‘The Physics of Star Trek’… a stable wormhole… can always be turned into a time machine… The problem… is that wormholes cannot be stable if normal matter and energy are all we have available to create one. Each mouth of the wormhole will collapse to form a black hole out of which nothing can escape in a time shorter than it would take to traverse the wormhole. The only way to stabilize a wormhole is to fill it up with a new, exotic kind of energy… and there are persuasive arguments that one cannot create, even in principle, such energy in the laboratory… knowing how to untangle the precise relativistic quantum properties of curved spacetimes is required to resolve the issue, and we don’t yet have the technology to do so.” (Pg. 34)
He explains, “space and time… become relativistic quantum mechanical variables. And relativistic quantum variables can spontaneously be created and destroyed. Whole ‘virtual’ spacetimes, like our own universe, could spontaneously pop into existence. But… only those spacetimes that have zero total energy might be expected to survive more than an instant, much less 13.8 billion years, before disappearing.” (Pg. 45-46)
He suggests, “if there is a multiverse, there may be no such fundamental principles. Many of the basic characteristics of our universe might be accidental. It could be that the laws of physics could be quite different in each universe within the multiverse, and that we measure the laws we do because our universe happened to allow the formation of galaxies, planets and life… If an infinite number of universes are formed over an infinite time, then the laws of probability suggest it is inevitable that there will be other universes just like our own… and everything we now see would exist as an exact copy, with perhaps a few exceptions. In that universe, the copy of you might be writing this book now, and the copy of me might … be reading it, for example… Every possibility that could exist, would exist…” (Pg. 55-56)
He recounts, “Physicists trying to develop a quantum theory of gravity … discovered a theory in which the fundamental spacetime objects were... string-like objects… The theory would indeed allow general relativity to be consistently quantized, but only if spacetime had not four dimensions, but twenty-six. This was a lot to swallow… for many physicists… a large cadre of very talented theorists … discovered that… it was possible to reduce the number of dimensions from twenty-six down to ten or eleven…. [But] if there are indeed other dimensions in nature, where are they hiding?... These extra dimensions could be curled up into a very small six- or seven-dimensional ball… The diameter of the ball would be … about nineteen orders of magnitude smaller than the diameter of the nucleus of a hydrogen atom!... For this reason… string theory remains a fascinating area of study … but whether it has anything to do with the real world remains an open question.” (Pg. 59-60)
He acknowledges, “it is possible to … outline the various key features that underlie our quantum universe… These five facts capture most of the craziness of quantum theory. They imply that the sensible classical reality that most of us take for granted is an illusion… physicists from Einstein onward have argued that while the mathematics of quantum mechanics clearly provides correct predictions about how the world works… quantum mechanics is simply too crazy to be absolutely true.” (Pg. 113-116)
He clarifies, ‘In my book, ‘A Universe from Nothing,’ I argued that quantum creation of universes from nothing is to be expected, and that the properties of such a universe will… inevitably resemble the properties of the universe in which we live. But I acknowledged … that simply having no space, no time, no particles, and no radiation, may not be fully NOTHING What about the laws of physics? Did they antedate our universe?” (Pg. 121)
He argues, “Some individuals who refuse to accept the likelihood of the natural formation of life and demand a supernatural explanation point to … complexity as a proof of the inadequacy of natural mechanisms to explain life’s appearance… The problem with this viewpoint is that, just like evolution, the origin of life weas likely not a completely random process. The laws of chemistry depend on the subtle interplay between the physical concepts of entropy… and enthalpy…” (Pg. 128-129)
He cautions, “many of the planets within their star’s habitable zones exist much closer to their host stars than the earth does to the sun… Thus, every time another earth-like planet is reported in the press, it is best to remain skeptical about the possibilities of finding life on it.” (Pg. 146)
He states, “perhaps, as… some scientists… like to imagine, life was INTENTIONALLY seeded on this planet by an advanced civilization… this notion… merely puts off the origins of life issue. If life on earth evolved because it was jump-started by life elsewhere, what about the life elsewhere? Was it seeded too? Eventually the buck will have to stop, and the non-biological origin of life will have to be explained. For this reason, I don’t really take panspermia seriously.” (Pg. 150)
He observes, “in a universe that expands FOREVER, there may be local fluctuations that might, with unbelievably small but NON-ZERO probabilities, cause momentary (in a cosmic sense) emergences of some news life forms. They too will die out, but the process may reoccur every now and then, forever. In that vague and improbable sense, life itself might never end in the universe. It just won’t be the same life that survives…” (Pg. 160)
He asserts, “the universe isn’t fine-tuned for life. Rather, life on earth arose because it could. Just s in the case of biological evolution, life is fine-tuned for the universe, rather than the other way around. The existence of life in our universe seems miraculous, but it need not be a miracle. The mysteries surrounding the origin of life, its variety, and its possible future are fascinating and provocative. The fact that we don’t yet fully understand these things is not evidence for God or that we live in some vast video game created by some more advanced civilization … Rather, it is simply evidence of not understanding, and that motivates trying to find out the answers… Not only are we not likely to be special gifts of creation, but the possible existence of lifeforms with nothing in common with us lends further incredulity to the incredibly non-humble suggestion that the universe was made for us.” (Pg. 162)
He admits, “the phenomenon of consciousness is the one area I know of in science where the forefront discussions seem to be made by philosophers equally as often as they are made by experimental cognitive scientists. I tend to view this as an indication of a science in its early stages. Philosophy is indispensable for developing the questions in fields of science where it is not clear what the important questions are, namely, the ones that scientists will use later to explore nature, which in turn lead to further questions, answers, and so on.” (Pg. 166-167)
He notes, “I have never liked the term artificial intelligence as it applies to the technologies we are creating, because there is, as far as I can see, nothing artificial or intelligent about it. Most of what is now classified as AI is really a case of machine learning (ML). With ML, computers sift through mountains of data. Faced with increasing amounts of data, real and imagined, internet companies are under immediate pressure to help develop software and hardware that can ‘learn’ from the data---that is, systems that can adapt to future real-time data inputs, using information gleaned from scouring massive amounts of past data.” (Pg. 192)
He asks, “The key question…is whether such an evolutionary history is… necessary to recreate consciousness in machines. Will devices that do not have the hierarchical framework of our brains---with forebrain and midbrain built on hindbrain, with succeeding layers taking on new tasks while interfacing and communicating across the entire system, all the while being intimately tied to bodily sensory information flow and regulation---be able to achieve consciousness? Time will tell. It may be that fundamentally new computational devices, perhaps based on quantum computing ideas, will be required. I personally suspect, no matter how challenging, that there is no fundamental roadblock getting in the way of ultimately developing functioning self-aware machines.” (Pg. 196)
He concludes, “What is called artificial intelligence is a natural by-product of human development, just as writing was then. Technology, a human invention, changes the world, but it also requires humans to change with it. This has been going on long as humans have been human. An AI future may be better than the present. After all, I imagine most people today think a world of books to read is better than the world before writing allowed them to be written. Recognizing that we don’t know what the future will bring, just as recognizing how many questions about the universe are yet to be answered, may help us ensure that the future always remains more exciting than the past.” (Pg. 199)
This book will be of great interest to those concerned with current issues in science.
August 20, 2024
Läst augusti 2024 i svensk översättning (ISBN 978-91-8973-314-5). Tanken var att få en introduktion i kosmologin, vilket inte är författarens avsikt med boken. Därför är de två sista kapitlen inte intressanta här.
Kul läsning, lagom nivå, ingen matte. Historiska beskrivningar om teoriutvecklingar.
Förord
De olösta gåtorna som boken ska behandla:
Hur började vårt universum, om det nu över huvud taget hade en början? Hur kommer det att sluta? Hur stort är det? Vad finns bortom det som vi kan se? Vilka är de naturlagar som styr vår tillvaro? Är de lagarna desamma överallt? Vad är den värld som vi upplever uppbyggd av? Vad förblir dolt för oss? Hur uppkom livet på jorden? Är vi ensamma i universum? Vad är medvetande för något? Är det mänskliga medvetandet unikt?
Boken har olika kapitel kring följande begrepp: tid, rum, materia, liv och medvetande.
Tid
Einstein kom i början av 1900-talet fram till att ljusets hastighet är observationsoberoende; därför måste mätningar av avstånd och tid vara tvärtom beroende av observatören. Den är inte ”objektiv”.
Sedan dess har teorin kunnat bevisas genom experiment med superexakta atomklockor, där den ena flög runt jorden och den andra var kvar kunde man visa att uret som hade flugigt runt jorden gick lite efter.
Men: Två observatörers referensramar är egentligen inte lika (ekvivalenta), om den ena upplever en acceleration, se tvillingparadoxen.
I arbetet med den allmänna relativitetsteorin jämförde Einstein att observatören befinner sig i ett accelererande system med att befinna sig i ett gravitationsfält. Detta har bevisats (1969) genom att mäta frekvensen av partiklar som rör sig genom ett gravitationsfält: när man placerar sändare och mottagare ovanför varandra och låter sedan sändaren röra sig neråt, registrerar mätaren en rödförskjutning. Uttryckt annorlunda: ”När ljus färdas uppåt, i motsatt riktning mot jordens dragningskraft, förlorar det energi.”
Den praktiska användningen av det är GPS: mottagare i en mobiltelefon registrerar signaler från olika sändare.
Om ljusets hastighet minskar, när det färdas i motsats riktning till dragningskraft, så finns det en gräns för gravitationens styrka som gör att ljusets hastighet inte räcker till. Det finns därmed objekt som är så tunga att inte ens ljus kan lämna objektet: svarta hål.
Runt ett svart hål finns en händelsehorisont, där tiden verkar stanna upp helt. Det är avståndet där inget ljus kommer ut, när ett objekt närmar sig svarta hålet. För en observatör ser objektet röra sig långsammare ju närmare det kommer händelsehorisonten, för att slutligen uppenbarligen stanna upp innan det ”försvinner” in i svarta hålet. Observatören ser alltså inte objektet hela vägen. För objektet själv märks ingen skillnad.
Tiden förändras med andra ord när man passerar händelsehorisonten: skillnaden mellan rum och tid försvinner och båda förenas i en fyrdimensionell rumtid. På samma sätt som rum är observatörsberoende i vårt tredimensionella rum, så blir tid observatörsberoende i rumtiden.
Vid centrum av svarta hålet förlorar både rum och tid sin mening, punkten kallas för singularitet. Istället för att beskrivas som en punkt med oändlig täthet, är det snarare en ändlig punkt i tiden med oändlig utsträckning.
Och så långt sträcker sig vår kunskap. Vad som händer i singulariteten vet vi inte, en övergång till ett annat universum kanske. Men det är bara spekulationer.
Om tiden kan ta slut, är det kanske möjligt att den har en start, vilket naturligtvis ställer från efter ”innan tiden”.
Fram till 1930 tänkte man sig att universum var statiskt och evigt. Men sedan kom Hubble 1929 och upptäckte att alla galaxer avlägsnar sig från oss i allt högre hastighet (rödförskjutning). Därmed blev det möjligt att beräkna början: för runt 13,8 miljarder år sedan växte vårt universum fram ur en singularitet.
Så på samma sätt som vårt universum tycks komma att sluta i en singularitet så verkar också haft sin ursprung i en singularitet. Men idén är inte populär: 1949 försökte Fred Hoyle att förlöjliga tanken genom att kalla det för big bang. Ordet är fel för att det inte var någon gigantisk explosion som gav upphov till universum, men namnet har fastnat.
1965 års upptäckt av bakgrundsstrålningen, en mikrovågsstrålning som är efterglöden av big bang, var det slutliga beviset.
Frågan som återstår är om tiden också kan ”resas tillbaka”, så som vi gör i rummet. Enligt allmänna relativitetsteorin borde det vara möjligt. Enda hittills tänkbara scenario är genom ett maskhål. Men med den materia och energi som vi idag känner till, finns det inga stabila maskhål.
Och angående universumets framtid så vet vi att den eviga och accelererande expansionen kommer att ha följden att andra galaxer inte kommer att kunna ses mera och att det svarta hålet i mitten av Vintergatan kommer att sluka allt. Och när, enligt Hawkingstrålning, även detta svarta hål så småningom avdunstar, så kommer det att finnas kvar … ingenting. Vi kommer sannolikt inte att få veta.
Rum
Om man tänker sig universum som ett klot, så tänker man vidare att ytan avgränsar ”allt som finns”. Inuti klotet finns det bara två dimensioner. Om går i en riktning så hamnar till slut på samma ställe som man startade ifrån. Om klotet blir större, så avlägsnar sig varje punkt från den andra. Så klotet expanderar utan att det finns något utanför.
På samma sätt kan universum vara slutet. Det är krökt och det saknas ett utanför, men det kan expandera.
Universum kan också vara plant, ingen krökning.
Eller så kan universum ha en negativ krökning. Då är det öppet och sträcker sig oändligt i alla riktningar.
Beroende på universums geometri är dess framtid. För att besvara den frågan behöver man veta om universum är plant (expandera allt långsammare men aldrig stanna upp), öppet (expandera för evigt i samma takt) eller slutet (expandera allt snabbare och till slut kollapsa).
Mest logiskt låter plant: genom sin konstanta expansion borde universum ha blivit plant. Men det finns ett problem: i alla mätningar visar det sig att den synliga materien ör bara 2% an den ”nödvändiga” materien för att åstadkomma ett plant universum. Det finns förvisso mörk materia, som inte interagerar med ljus eller elektromagnetisk strålning och därför inte kan observeras.
Men sammanlagt utgör synlig och mörk materia bara upp till 30% av det som väntas. Resten måste vara mörk energi, som är energi i tomma rummet. Och den är ansvarig för att expansionen sker allt snabbare.
Vad som talar för ett plant universum är expansionen, för att en oändlig expansion borde ha åstadkommit det. Den synliga materien räcker förvisso inte till, men man upptäckte både mörk materia och mörk energi, som är förutsättningarna för en (oändlig och accelererande) expansion. Dessvärre kommer vi inte kunna ”mäta” det, för att det ligger i sakens natur att mindre och mindre av universum kommer att vara synligt.
”Ser vi bortom inflationen och begrundar ursprunget till själva rummet finner vi goda skäl att tro att rummet som omger den synliga delen av vårt universum måste vara slutet.” Fast då måste den totala energin i universum vara noll.
Betraktar man topologin, skulle det kunna vara så att universum har en icke-trivial topologi (jämför en torus). Där har man en plan yta och räta linjer som förblir det. På samma sätt skulle universum fungera: plant men ändå ändligt. Idén har undersökts av Roger Penrose.
En fråga är: Går det att observera vad som egentligen är bortom de synliga delarna av universum? Det enda som finns att titta på är rester av kvantprocesser som sker under inflationen, s k kvantflutktuationer. De lämnar spår i form av små täthetsvariatoner. De i sin tur ger upphov till bildandet av galaxer. De kan mätas som fluktuationer i bakgrundsstrålningen. På samma sätt skulle det finnas fluktuationer i gravitationsfältet, i så fall mätbara som gravitationsvågor i bakgrundsstrålningen.
För att kunna bevisa att inflationen har ägd rum, försöker man mäta om det finns en specifik polarisation i bakgrundsstrålningen och även om det finns gravitationsvågor som skapats av inflationen; det har inte lyckats än. Om man hade det beviset, hade man därmed också funnit ett svar efter multiversum. Men det - om något - är spekulationer.
Intresset för flera dimensioner kan föras tillbaka till Einstein och Maxwell. Einstein beskrev gravitationen som en kraft som är förknippad med rumtidens krökning. Den skiljer sig från de tre andra krafterna, men beter sig mest som elektromagnetism: båda avtar med kvadraten på avståndet, den ena är proportionell mot massan, den andra mot laddningen. Även det elektromagnetiska fältet kan beskrivas så att det avspeglar en krökning, dock inte i det verkliga rummet utan i ett ”internt matematiskt rum”. Det har Kaluza och Klein undersökt: det kanske finns en osynlig, femte dimension, som kanske är ”ihoprullat i en cirkel och mycket liten. Det låter som en bisarr idé. Men sextio år senare kom strängteorin och föreslog att fundamentala objekt inte är punkter utan strängar. Man kunde därmed ”kvantisera den allmänna relativitetsteorin”, men med ett pris: rumtiden behöver ha 26 dimensioner; sedan har siffran ändrats till 10 eller 11. De nödvändiga 6 eller 7 extra-dimensionerna räknar man sig väldigt små och ihoprullade.
Materia
Standardmodellen fungerar för att förklara och framför allt förutsäga resultat i alla experiment i den subatomära skalan. Men:
* Standardmodellen är ofullständig, man behöver upp till 18 parameter / konstanter som måste användas för att få matematiken att fungera.
* Det finns det vi kallar mörk materia, mörk energi och neutrinernas massa som vi inte förstår.
* Gravitationen som inte passar ihop med kvantmekaniken.
En utvikning om neutroners sönderfall: 1932 upptäckte James Chadwick neutronen. Då förstod man att kärnor består av protoner och neutroner - det ger de deras massa. Samtidigt kan antalet protoner matcha antalet elektroner - alla partiklar behöver inte vara protoner.
Neutroner faller sönder till en proton och en elektron. Men energimängden efter sönderfallet är inte tillräcklig, om det inte finns ytterligare en partikel iblandad. Det visade sig vara neutrino, föreslagit 1930 av Pauli och upptäckt 1956 av Reines och Crowe. Neutriner är mycket lätta, oladdade och växelverkar (nästan) inte alls.
Många elementarpartiklar (elektroner, protoner, neutroner) har ett rörelsemängdsmoment: de har en spinn på 1/2 - spinn verkar vara en usel benämning för att det handlar inte alls om rotation, utan ”bara” att partiklarna blir avledda (?), som om de vore magneter.
Beroende på om rörelsemängdsmomentet går i den ena riktningen är det +1/2 eller -1/2, eller med andra ord höger- eller vänsterhänt. Pariteten kan också variera: antingen udda eller jämt.
Neutriner är de enda partiklarna som har en spinn som är riktat åt motsatt håll jämfört med rörelseriktningen, de är vänsterhänta. Men så känner neutriner också bara av den svaga växelverkan. Andra partiklar (t ex elektroner) som kan vara både höger- och vänsterhänta och känner av både den svaga växelverkan och elektromagnetism påverkas olika av den första, beroende på om de är höger- eller vänsterhänta.
Skillnaden mellan den svaga kraften och elektromagnetism är att den första verkar i extremt små skalor medan den andra verkar över jättelånga avstånd. Man tänker sig att det beror på att den andra verkar via lätta partiklar, nämligen fotoner. Då borde, i analogi, den svaga kraften verka på extremt tunga partiklar.
Då föreslog (bland andra Higgs) att alla elementarpartiklar egentligen saknar massa, alls. Istället - vet vi numera - finns det ett fält, som alla partiklar växelverkar med, olika mycket, och därmed ”verkar ha massa”, ungefär som när det är trögt att trycka ner en spade i lera.
Higgsbosonerna hittades och därmed fältet som de åstadkommer. Det visade sig att de saknar spinn; därmed är de känsliga för effekterna av kvantprocesser, som kan skapa virtuella partiklar. De i sin tur kan inverka på verkliga partiklars massa.
Men det uppenbarar sig en lucka i vår kunskap som har med energinivån för svag kraft och för kvantgravitation att göra. Ett försök att lösa det är teorin om supersymmetri.
Fermioner (elektroner, protoner, neutroner, neutriner) har spin 1/2. Bosoner (fotoner, W- och Z-partiklar) har spinn 1. Enligt Pauli-principen kan inte två identiska fermioner ha samma kvanttillstånd samtidigt. Enligt supersymmetrin har varje fermion en ”partner-boson”. Men tyvärr går det inte att påvisa dessa ”partners”. Så supersymmetrin går inte att påvisa - i dagsläget, vilket är dåligt för standardmodellen.
Protoner och neutroner, till skillnad från elektroner, är inte fundamentala, utan uppbyggda av kvarkar. De väntades ha bråkdelsladdning, vilket ”kändes” osannolikt, med de påvisades 1969. De påverkas av den starka växelkraften, som är starkare ju längre kvarkarna rör sig från varandra, vilket sammanfattas i teorin om kvantkromodynamik.
Tidigare (1929) hade Wolfgang Pauli förenat kvantmekanik med speciella relativitetsteorin som fick benämningen kvantelektrodynamik. I den ingick förutsägelsen om en slags elektron med positiv laddning och den upptäcktes redan 1932 av Carl Anderson.
Kvantelektrodynamiken säger med andra ord att det för varje elementarpartikel måste en antipartikel med samma massa men motsatt laddning - och de har påvisats.
Men de kommer nästa problem: varför - trots att materia och antimateria direkt omvandlas till strålning och slutar existera som materia - finns det mer materia än antimateria? Vi finns ju, trots allt. Problemet är känt som baryonasymmetri (från benämningen baryon för protoner och neutroner). Obalansen borde ha funnits sedan universumets uppkomst.
Andrej Sacharov skrev redan 1969 en artikel med tre villkor för att detta skulle kunna uppstå:
1. Interaktioner som skulle öka eller minska antalet baryoner.
2. En avvikelse från termisk jämnvikt i det tidig universum.
3. Ett brott mot symmetrin mellan partiklar och antipartiklar.
Efter många decennier av experiment kom man fram till att det finns flera ”familjer” av partiklar (kvarkar och leptoner). Kvarkar kan delas in i tre grupper:
* upp- och ner-kvarkar
* botten- och top-kvarkar
* sär- och charm-kvarkar
och deras anti-kvarkar. Den första gruppen är stabil och ger upphov till materia, medan de två sista grupperna är instabila och finns egentligen bara i acceleratorer, dvs. när de skapas i experiment.
Leptoner delas också in i tre grupper:
* elektron och elektronneutrino
* myon och myonneutrino
* tauon och tauonneutrino
Men: problemet med asymmetrin mellan materia och antimateria är inte löst.
Vidare finns det frågor kring naturkrafterna: Finns det fler än de fyra vi känner till (gravitation, elektromagnetism, svag och stark växelverkan?
Tre av krafterna (förutom gravitationen) förenas vid höga energier. Men gravitationen passar inte in, än. Och det gör att supersymmetrin och storförenade teorin (GUT) inte kan bevisas.
Neutriner saknar (i princip) massa och är alltid vänsterhänta: deras rörelsemängdsmoment hos deras spinn pekar åt motsatt håll i förhållande till rörelseriktningen. När man försökte hitta neutrinerna som kommer från solen i experiment (Ray Davis, 1965) kunde man bara mäta runt 30% av det väntade antalet. Men ett annat experiment 2001, som tog i beräkning att neutriner ändå har nasse (om än väldigt lite massa) hittade alla väntade. Så neutriner har lite massa. Men då behöver neutriner nödvändigtvis också finnas som högerhänta. Här finns kanske en lösning för GUT: den s k leptonasymmetri.
Sammanfattning av ”top” med kvantmekaniken:
1. Kvantobjekt kan befinna sig i många olika tillstånd samtidigt. En mängd elektroner som skickas ut från ett katodstrålerör rör sig ”som grupp” enligt Newtons lagar, i en väldefinierad bana, men banan för en enstaka elektron är inte förutbestämt - förutom när man gör mätningen. Elektronen uppför sig som om den följde flera banor samtidigt.
2. Objektets vågfunktioner ger en exakt förutsägelse av sannolikheten för objektets tillstånd. På det viset är kvantmekaniken deterministisk. Den är inte ”slumpvis”. Men den anger sannolikheten.
3. Ordningen som man mäter ett objekts egenskaper påverkar mätningens resultat; detta är Heisenbergs osäkerhetsprincip.
4. ”Om ett system av flera i övrigt separata objekt befinner sig i något visst kvanttillstånd fortsätter objekten att vara koherent korrelerade med varandra även om de blir fysiskt åtskilda, så länge systemet förblir ostört.” Detta är sammanflätning, quantum entaglement.
5. När kvantmekaniken kombineras med relativitetsteorin blir det ännu mera underligt. Partiklar och antipartiklar kan uppstå spontant, även om de försvinner så snabbt att de inte kan påvisas. Med andra ord: kvantsystem fluktuerar.
Och för att det är på detta viset - matematiken säger det - och även om det fullständigt strider mot vår uppfattning av verkligheten, är det enda vi kan göra att acceptera att kvantmekaniken beskriver verkligheten, vår värld.
Även om Schrödingers katt skulle vara liten kan den ju inte samtidigt vara både levande och död innan jag öppnar lådan för att iaktta den.” Bäst att förklara denna ”obegriplighet” var John Stewart Bell, som triggade massa med praktiska experiment, se Sidney Colemans föreläsning ”Quantum mechanics in your face”, https://arxiv.org/pdf/2011.12671. Vårt problem med att förstå kvantmekaniken är egentligen ett semantiskt problem: vi ska inte tänka oss en slags ”tolkning av kvantmekaniken” utan en tolkning av den klassiska mekaniken.
”Kvantmekaniken innefattar och ersätter den klassiska mekaniken. Den ger samma resultat som den klassiska mekaniken i skalor där kvanteffekterna försvinner, precis som den allmänna relativitetsteorin förenklas till newtonsk gravitationsteori när gravitationsfälten är svaga. Men ingen förväntar sig att de allmänrelativistiska förutsägelserna av beteenden i starkt krökta rum på ett rimligt vis skulle kunna återges inom ramen för ett newtonskt synsätt där rummet är plant.” Därför ska man inte tänka på det sättet med kvantmekaniken heller.
Det svåra med kvantmekaniken är kanske att den strider både mot våra direkta erfarenheter och mot klassisk logik och bevisföring. Men: ”Slutskedet vid uppkomsten av svarta hål, de svarta hålens avdunsta, den skenbara singulariteten vid big bang, kvantmekanisk tillblivelse av nya universum - allt detta kommer att behöva omvärderas radikalt om kvantmekaniken underordnas någon mer fundamental dynamik i de minsta storleksskalorna.”
Kul läsning, lagom nivå, ingen matte. Historiska beskrivningar om teoriutvecklingar.
Förord
De olösta gåtorna som boken ska behandla:
Hur började vårt universum, om det nu över huvud taget hade en början? Hur kommer det att sluta? Hur stort är det? Vad finns bortom det som vi kan se? Vilka är de naturlagar som styr vår tillvaro? Är de lagarna desamma överallt? Vad är den värld som vi upplever uppbyggd av? Vad förblir dolt för oss? Hur uppkom livet på jorden? Är vi ensamma i universum? Vad är medvetande för något? Är det mänskliga medvetandet unikt?
Boken har olika kapitel kring följande begrepp: tid, rum, materia, liv och medvetande.
Tid
Einstein kom i början av 1900-talet fram till att ljusets hastighet är observationsoberoende; därför måste mätningar av avstånd och tid vara tvärtom beroende av observatören. Den är inte ”objektiv”.
Sedan dess har teorin kunnat bevisas genom experiment med superexakta atomklockor, där den ena flög runt jorden och den andra var kvar kunde man visa att uret som hade flugigt runt jorden gick lite efter.
Men: Två observatörers referensramar är egentligen inte lika (ekvivalenta), om den ena upplever en acceleration, se tvillingparadoxen.
I arbetet med den allmänna relativitetsteorin jämförde Einstein att observatören befinner sig i ett accelererande system med att befinna sig i ett gravitationsfält. Detta har bevisats (1969) genom att mäta frekvensen av partiklar som rör sig genom ett gravitationsfält: när man placerar sändare och mottagare ovanför varandra och låter sedan sändaren röra sig neråt, registrerar mätaren en rödförskjutning. Uttryckt annorlunda: ”När ljus färdas uppåt, i motsatt riktning mot jordens dragningskraft, förlorar det energi.”
Den praktiska användningen av det är GPS: mottagare i en mobiltelefon registrerar signaler från olika sändare.
Om ljusets hastighet minskar, när det färdas i motsats riktning till dragningskraft, så finns det en gräns för gravitationens styrka som gör att ljusets hastighet inte räcker till. Det finns därmed objekt som är så tunga att inte ens ljus kan lämna objektet: svarta hål.
Runt ett svart hål finns en händelsehorisont, där tiden verkar stanna upp helt. Det är avståndet där inget ljus kommer ut, när ett objekt närmar sig svarta hålet. För en observatör ser objektet röra sig långsammare ju närmare det kommer händelsehorisonten, för att slutligen uppenbarligen stanna upp innan det ”försvinner” in i svarta hålet. Observatören ser alltså inte objektet hela vägen. För objektet själv märks ingen skillnad.
Tiden förändras med andra ord när man passerar händelsehorisonten: skillnaden mellan rum och tid försvinner och båda förenas i en fyrdimensionell rumtid. På samma sätt som rum är observatörsberoende i vårt tredimensionella rum, så blir tid observatörsberoende i rumtiden.
Vid centrum av svarta hålet förlorar både rum och tid sin mening, punkten kallas för singularitet. Istället för att beskrivas som en punkt med oändlig täthet, är det snarare en ändlig punkt i tiden med oändlig utsträckning.
Och så långt sträcker sig vår kunskap. Vad som händer i singulariteten vet vi inte, en övergång till ett annat universum kanske. Men det är bara spekulationer.
Om tiden kan ta slut, är det kanske möjligt att den har en start, vilket naturligtvis ställer från efter ”innan tiden”.
Fram till 1930 tänkte man sig att universum var statiskt och evigt. Men sedan kom Hubble 1929 och upptäckte att alla galaxer avlägsnar sig från oss i allt högre hastighet (rödförskjutning). Därmed blev det möjligt att beräkna början: för runt 13,8 miljarder år sedan växte vårt universum fram ur en singularitet.
Så på samma sätt som vårt universum tycks komma att sluta i en singularitet så verkar också haft sin ursprung i en singularitet. Men idén är inte populär: 1949 försökte Fred Hoyle att förlöjliga tanken genom att kalla det för big bang. Ordet är fel för att det inte var någon gigantisk explosion som gav upphov till universum, men namnet har fastnat.
1965 års upptäckt av bakgrundsstrålningen, en mikrovågsstrålning som är efterglöden av big bang, var det slutliga beviset.
Frågan som återstår är om tiden också kan ”resas tillbaka”, så som vi gör i rummet. Enligt allmänna relativitetsteorin borde det vara möjligt. Enda hittills tänkbara scenario är genom ett maskhål. Men med den materia och energi som vi idag känner till, finns det inga stabila maskhål.
Och angående universumets framtid så vet vi att den eviga och accelererande expansionen kommer att ha följden att andra galaxer inte kommer att kunna ses mera och att det svarta hålet i mitten av Vintergatan kommer att sluka allt. Och när, enligt Hawkingstrålning, även detta svarta hål så småningom avdunstar, så kommer det att finnas kvar … ingenting. Vi kommer sannolikt inte att få veta.
Rum
Om man tänker sig universum som ett klot, så tänker man vidare att ytan avgränsar ”allt som finns”. Inuti klotet finns det bara två dimensioner. Om går i en riktning så hamnar till slut på samma ställe som man startade ifrån. Om klotet blir större, så avlägsnar sig varje punkt från den andra. Så klotet expanderar utan att det finns något utanför.
På samma sätt kan universum vara slutet. Det är krökt och det saknas ett utanför, men det kan expandera.
Universum kan också vara plant, ingen krökning.
Eller så kan universum ha en negativ krökning. Då är det öppet och sträcker sig oändligt i alla riktningar.
Beroende på universums geometri är dess framtid. För att besvara den frågan behöver man veta om universum är plant (expandera allt långsammare men aldrig stanna upp), öppet (expandera för evigt i samma takt) eller slutet (expandera allt snabbare och till slut kollapsa).
Mest logiskt låter plant: genom sin konstanta expansion borde universum ha blivit plant. Men det finns ett problem: i alla mätningar visar det sig att den synliga materien ör bara 2% an den ”nödvändiga” materien för att åstadkomma ett plant universum. Det finns förvisso mörk materia, som inte interagerar med ljus eller elektromagnetisk strålning och därför inte kan observeras.
Men sammanlagt utgör synlig och mörk materia bara upp till 30% av det som väntas. Resten måste vara mörk energi, som är energi i tomma rummet. Och den är ansvarig för att expansionen sker allt snabbare.
Vad som talar för ett plant universum är expansionen, för att en oändlig expansion borde ha åstadkommit det. Den synliga materien räcker förvisso inte till, men man upptäckte både mörk materia och mörk energi, som är förutsättningarna för en (oändlig och accelererande) expansion. Dessvärre kommer vi inte kunna ”mäta” det, för att det ligger i sakens natur att mindre och mindre av universum kommer att vara synligt.
”Ser vi bortom inflationen och begrundar ursprunget till själva rummet finner vi goda skäl att tro att rummet som omger den synliga delen av vårt universum måste vara slutet.” Fast då måste den totala energin i universum vara noll.
Betraktar man topologin, skulle det kunna vara så att universum har en icke-trivial topologi (jämför en torus). Där har man en plan yta och räta linjer som förblir det. På samma sätt skulle universum fungera: plant men ändå ändligt. Idén har undersökts av Roger Penrose.
En fråga är: Går det att observera vad som egentligen är bortom de synliga delarna av universum? Det enda som finns att titta på är rester av kvantprocesser som sker under inflationen, s k kvantflutktuationer. De lämnar spår i form av små täthetsvariatoner. De i sin tur ger upphov till bildandet av galaxer. De kan mätas som fluktuationer i bakgrundsstrålningen. På samma sätt skulle det finnas fluktuationer i gravitationsfältet, i så fall mätbara som gravitationsvågor i bakgrundsstrålningen.
För att kunna bevisa att inflationen har ägd rum, försöker man mäta om det finns en specifik polarisation i bakgrundsstrålningen och även om det finns gravitationsvågor som skapats av inflationen; det har inte lyckats än. Om man hade det beviset, hade man därmed också funnit ett svar efter multiversum. Men det - om något - är spekulationer.
Intresset för flera dimensioner kan föras tillbaka till Einstein och Maxwell. Einstein beskrev gravitationen som en kraft som är förknippad med rumtidens krökning. Den skiljer sig från de tre andra krafterna, men beter sig mest som elektromagnetism: båda avtar med kvadraten på avståndet, den ena är proportionell mot massan, den andra mot laddningen. Även det elektromagnetiska fältet kan beskrivas så att det avspeglar en krökning, dock inte i det verkliga rummet utan i ett ”internt matematiskt rum”. Det har Kaluza och Klein undersökt: det kanske finns en osynlig, femte dimension, som kanske är ”ihoprullat i en cirkel och mycket liten. Det låter som en bisarr idé. Men sextio år senare kom strängteorin och föreslog att fundamentala objekt inte är punkter utan strängar. Man kunde därmed ”kvantisera den allmänna relativitetsteorin”, men med ett pris: rumtiden behöver ha 26 dimensioner; sedan har siffran ändrats till 10 eller 11. De nödvändiga 6 eller 7 extra-dimensionerna räknar man sig väldigt små och ihoprullade.
Materia
Standardmodellen fungerar för att förklara och framför allt förutsäga resultat i alla experiment i den subatomära skalan. Men:
* Standardmodellen är ofullständig, man behöver upp till 18 parameter / konstanter som måste användas för att få matematiken att fungera.
* Det finns det vi kallar mörk materia, mörk energi och neutrinernas massa som vi inte förstår.
* Gravitationen som inte passar ihop med kvantmekaniken.
En utvikning om neutroners sönderfall: 1932 upptäckte James Chadwick neutronen. Då förstod man att kärnor består av protoner och neutroner - det ger de deras massa. Samtidigt kan antalet protoner matcha antalet elektroner - alla partiklar behöver inte vara protoner.
Neutroner faller sönder till en proton och en elektron. Men energimängden efter sönderfallet är inte tillräcklig, om det inte finns ytterligare en partikel iblandad. Det visade sig vara neutrino, föreslagit 1930 av Pauli och upptäckt 1956 av Reines och Crowe. Neutriner är mycket lätta, oladdade och växelverkar (nästan) inte alls.
Många elementarpartiklar (elektroner, protoner, neutroner) har ett rörelsemängdsmoment: de har en spinn på 1/2 - spinn verkar vara en usel benämning för att det handlar inte alls om rotation, utan ”bara” att partiklarna blir avledda (?), som om de vore magneter.
Beroende på om rörelsemängdsmomentet går i den ena riktningen är det +1/2 eller -1/2, eller med andra ord höger- eller vänsterhänt. Pariteten kan också variera: antingen udda eller jämt.
Neutriner är de enda partiklarna som har en spinn som är riktat åt motsatt håll jämfört med rörelseriktningen, de är vänsterhänta. Men så känner neutriner också bara av den svaga växelverkan. Andra partiklar (t ex elektroner) som kan vara både höger- och vänsterhänta och känner av både den svaga växelverkan och elektromagnetism påverkas olika av den första, beroende på om de är höger- eller vänsterhänta.
Skillnaden mellan den svaga kraften och elektromagnetism är att den första verkar i extremt små skalor medan den andra verkar över jättelånga avstånd. Man tänker sig att det beror på att den andra verkar via lätta partiklar, nämligen fotoner. Då borde, i analogi, den svaga kraften verka på extremt tunga partiklar.
Då föreslog (bland andra Higgs) att alla elementarpartiklar egentligen saknar massa, alls. Istället - vet vi numera - finns det ett fält, som alla partiklar växelverkar med, olika mycket, och därmed ”verkar ha massa”, ungefär som när det är trögt att trycka ner en spade i lera.
Higgsbosonerna hittades och därmed fältet som de åstadkommer. Det visade sig att de saknar spinn; därmed är de känsliga för effekterna av kvantprocesser, som kan skapa virtuella partiklar. De i sin tur kan inverka på verkliga partiklars massa.
Men det uppenbarar sig en lucka i vår kunskap som har med energinivån för svag kraft och för kvantgravitation att göra. Ett försök att lösa det är teorin om supersymmetri.
Fermioner (elektroner, protoner, neutroner, neutriner) har spin 1/2. Bosoner (fotoner, W- och Z-partiklar) har spinn 1. Enligt Pauli-principen kan inte två identiska fermioner ha samma kvanttillstånd samtidigt. Enligt supersymmetrin har varje fermion en ”partner-boson”. Men tyvärr går det inte att påvisa dessa ”partners”. Så supersymmetrin går inte att påvisa - i dagsläget, vilket är dåligt för standardmodellen.
Protoner och neutroner, till skillnad från elektroner, är inte fundamentala, utan uppbyggda av kvarkar. De väntades ha bråkdelsladdning, vilket ”kändes” osannolikt, med de påvisades 1969. De påverkas av den starka växelkraften, som är starkare ju längre kvarkarna rör sig från varandra, vilket sammanfattas i teorin om kvantkromodynamik.
Tidigare (1929) hade Wolfgang Pauli förenat kvantmekanik med speciella relativitetsteorin som fick benämningen kvantelektrodynamik. I den ingick förutsägelsen om en slags elektron med positiv laddning och den upptäcktes redan 1932 av Carl Anderson.
Kvantelektrodynamiken säger med andra ord att det för varje elementarpartikel måste en antipartikel med samma massa men motsatt laddning - och de har påvisats.
Men de kommer nästa problem: varför - trots att materia och antimateria direkt omvandlas till strålning och slutar existera som materia - finns det mer materia än antimateria? Vi finns ju, trots allt. Problemet är känt som baryonasymmetri (från benämningen baryon för protoner och neutroner). Obalansen borde ha funnits sedan universumets uppkomst.
Andrej Sacharov skrev redan 1969 en artikel med tre villkor för att detta skulle kunna uppstå:
1. Interaktioner som skulle öka eller minska antalet baryoner.
2. En avvikelse från termisk jämnvikt i det tidig universum.
3. Ett brott mot symmetrin mellan partiklar och antipartiklar.
Efter många decennier av experiment kom man fram till att det finns flera ”familjer” av partiklar (kvarkar och leptoner). Kvarkar kan delas in i tre grupper:
* upp- och ner-kvarkar
* botten- och top-kvarkar
* sär- och charm-kvarkar
och deras anti-kvarkar. Den första gruppen är stabil och ger upphov till materia, medan de två sista grupperna är instabila och finns egentligen bara i acceleratorer, dvs. när de skapas i experiment.
Leptoner delas också in i tre grupper:
* elektron och elektronneutrino
* myon och myonneutrino
* tauon och tauonneutrino
Men: problemet med asymmetrin mellan materia och antimateria är inte löst.
Vidare finns det frågor kring naturkrafterna: Finns det fler än de fyra vi känner till (gravitation, elektromagnetism, svag och stark växelverkan?
Tre av krafterna (förutom gravitationen) förenas vid höga energier. Men gravitationen passar inte in, än. Och det gör att supersymmetrin och storförenade teorin (GUT) inte kan bevisas.
Neutriner saknar (i princip) massa och är alltid vänsterhänta: deras rörelsemängdsmoment hos deras spinn pekar åt motsatt håll i förhållande till rörelseriktningen. När man försökte hitta neutrinerna som kommer från solen i experiment (Ray Davis, 1965) kunde man bara mäta runt 30% av det väntade antalet. Men ett annat experiment 2001, som tog i beräkning att neutriner ändå har nasse (om än väldigt lite massa) hittade alla väntade. Så neutriner har lite massa. Men då behöver neutriner nödvändigtvis också finnas som högerhänta. Här finns kanske en lösning för GUT: den s k leptonasymmetri.
Sammanfattning av ”top” med kvantmekaniken:
1. Kvantobjekt kan befinna sig i många olika tillstånd samtidigt. En mängd elektroner som skickas ut från ett katodstrålerör rör sig ”som grupp” enligt Newtons lagar, i en väldefinierad bana, men banan för en enstaka elektron är inte förutbestämt - förutom när man gör mätningen. Elektronen uppför sig som om den följde flera banor samtidigt.
2. Objektets vågfunktioner ger en exakt förutsägelse av sannolikheten för objektets tillstånd. På det viset är kvantmekaniken deterministisk. Den är inte ”slumpvis”. Men den anger sannolikheten.
3. Ordningen som man mäter ett objekts egenskaper påverkar mätningens resultat; detta är Heisenbergs osäkerhetsprincip.
4. ”Om ett system av flera i övrigt separata objekt befinner sig i något visst kvanttillstånd fortsätter objekten att vara koherent korrelerade med varandra även om de blir fysiskt åtskilda, så länge systemet förblir ostört.” Detta är sammanflätning, quantum entaglement.
5. När kvantmekaniken kombineras med relativitetsteorin blir det ännu mera underligt. Partiklar och antipartiklar kan uppstå spontant, även om de försvinner så snabbt att de inte kan påvisas. Med andra ord: kvantsystem fluktuerar.
Och för att det är på detta viset - matematiken säger det - och även om det fullständigt strider mot vår uppfattning av verkligheten, är det enda vi kan göra att acceptera att kvantmekaniken beskriver verkligheten, vår värld.
Även om Schrödingers katt skulle vara liten kan den ju inte samtidigt vara både levande och död innan jag öppnar lådan för att iaktta den.” Bäst att förklara denna ”obegriplighet” var John Stewart Bell, som triggade massa med praktiska experiment, se Sidney Colemans föreläsning ”Quantum mechanics in your face”, https://arxiv.org/pdf/2011.12671. Vårt problem med att förstå kvantmekaniken är egentligen ett semantiskt problem: vi ska inte tänka oss en slags ”tolkning av kvantmekaniken” utan en tolkning av den klassiska mekaniken.
”Kvantmekaniken innefattar och ersätter den klassiska mekaniken. Den ger samma resultat som den klassiska mekaniken i skalor där kvanteffekterna försvinner, precis som den allmänna relativitetsteorin förenklas till newtonsk gravitationsteori när gravitationsfälten är svaga. Men ingen förväntar sig att de allmänrelativistiska förutsägelserna av beteenden i starkt krökta rum på ett rimligt vis skulle kunna återges inom ramen för ett newtonskt synsätt där rummet är plant.” Därför ska man inte tänka på det sättet med kvantmekaniken heller.
Det svåra med kvantmekaniken är kanske att den strider både mot våra direkta erfarenheter och mot klassisk logik och bevisföring. Men: ”Slutskedet vid uppkomsten av svarta hål, de svarta hålens avdunsta, den skenbara singulariteten vid big bang, kvantmekanisk tillblivelse av nya universum - allt detta kommer att behöva omvärderas radikalt om kvantmekaniken underordnas någon mer fundamental dynamik i de minsta storleksskalorna.”
June 9, 2023
I really wanted to like this but I just didn’t find Krauss’s writing style to be all that engaging. Also, there were a non-zero number of Woody Allen references and that’s just far too many for a book published in 2023.
September 23, 2023
The Edge of Knowledge: Unsolved Mysteries of the Cosmos by Lawrence M. Krauss
“The Edge of Knowledge” renowned theoretical physicist and bestselling author Lawrence Krauss examines the threshold of the unknown and explores how far science has progressed. This stimulating 235-page book includes the following five chapters: 1. Time, 2. Space, 3. Matter, 4. Life, and 5. Consciousness.
Positives:
1. Well-written and well-researched book.
2. The fascinating topic of mysteries of the cosmos in the capable hands of Professor Krauss.
3. Krauss does a commendable effort of simplifying complex topics. His writing style is somewhat casual but he makes clear what we know versus what we don’t know. Each chapter begins with philosophical questions and quotes that are topic-appropriate followed by a stimulating discussion.
4. The concept of time. “Time and space are relative, and “now” only has an objective meaning for events that happen where you are located, so “now” is not a universal concept throughout the universe.”
5. Explains the key differences on when to apply Newtonian physics and not. “We now know that Newton’s law of gravity is not the correct theory to use when escape velocities approach the speed of light. Instead, we must resort to general relativity, which allows for the curvature of space as well as time dilation.”
6. Interesting facts throughout the book. “Since reaction rates increase exponentially with temperature, and temperature skyrockets as one approaches t=0, it is possible to estimate that more reactions occurred between particles in the first second of the history of the universe than will likely occur in the entire future history of the universe, even if that history is eternal! In this sense, we were born after almost all the good stuff happened.”
7. Understanding the importance of identifying the geometric pattern of space. “Namely, the ultimate future of the universe depends simply on whether the universe is open, closed, or flat, which is why determining which geometric pattern described our universe became the holy grail of cosmology.”
8. Discusses major findings in physics. “The Laser Interferometer Gravitational Wave (LIGO) observatory’s discovery of gravitational waves from colliding black holes on September 14, 2015, was a monumental achievement in physics, worthy of the 2017 Nobel Prize that was awarded to its developers.”
9. Discusses the main theories behind quantum gravity. “I consider string theory to be the leading candidate for a theory of quantum gravity, although that does not mean I think it is likely to be the correct theory.”
10. Discusses the biggest mystery in particle physics. “My favorite elementary particles in nature, neutrinos—ethereal particles released during nuclear reactions, whose interactions with normal matter are so weak that neutrinos streaming at us from the nuclear reactions inside the sun can go right through the earth without a single interaction—have a mass that is not predicted in the Standard Model, or even easily accommodated within it. Some new physics must be involved. We just don’t know what.”
11. The mystery of gravity. “Gravity stands out among the four known forces in nature because classical general relativity is incompatible with quantum mechanics.”
12. Throughout the book Krauss makes references to the giants of physics. “In 1929, the British theoretical physicist Paul Dirac figured out a way to unify quantum mechanics and special relativity, in turn producing a quantum theory of electromagnetism called quantum electrodynamics. It was a remarkable achievement that placed Dirac in the ranks of the greatest theoretical physicists of the twentieth century.”
13. Provides an outline of our quantum universe. “The fundamental quantity in quantum mechanics is the wavefunction of an object, which, succinctly, allows an exact prediction of the probability of measuring the object in any one of the allowed states it may be measured to be in, for all times.”
14. Describes science. “Science is about processes, about understanding dynamics—and that is what I want to focus on.”
15. The fascinating science of the origin of life. “While the details of the origin of life remain among the great unknowns of science, through a series of baby steps—interspersed with periodic giant leaps over the past fifty years—it is now not unreasonable to think that this mystery may be resolved in the coming decades.”
16. Is there life elsewhere in the universe? “Evidence of liquid water having flowed on its surface in the past, along with substantial evidence of water on or beneath its surface in places, has raised hopes of finding evidence for past or present life. Water is, after all, the source of life on earth.”
17. Explores consciousness. “There are now two ways of considering the role of consciousness in this picture. In the first, items in this workspace become conscious thoughts by virtue of being brought to the front layer of the monitor window—that is, being broadcast. In the second, all the windows are part of our consciousness.”
18. The evolution of language. “Chomsky has argued that language evolved as a part of neural circuitry that effectively generates thoughts, making modern cognition, reflection, and self-awareness possible. Internally generated thoughts can then sometimes be externalized via a sensory-motor medium and then used for communication.”
19. Describes the brain. “The brain is at the very least a distributed processing system, with multiple routes for information flow and processing, multiple centers, and many inputs for and alterations of cognitive states that we are not consciously aware of.”
20. Provocative statements. “As I have often said, not understanding something is not evidence for God or human frailty. It is just evidence of not understanding. And it should be an invitation to explore and learn.”
Negatives:
1. Regardless of the commendable effort to simplify such complex topics; many topics are beyond even the basic comprehension of the layperson. Quantum mechanics is not for the faint of heart.
2. There are better books covering some of the topics in more detail.
3. Lack of supplementary material.
In summary, this is a solid and stimulating book that explores the unknowns based on a solid foundation of science. Krauss covers five topics and provides readers a lot to digest. Each chapter begins with stimulating questions and topic-appropriate quotes followed by a narrative that pursue the answers. The book is brief but the discussion is substantive and Krauss succeeds in inspiring further pursuits. I recommend it.
Further recommendations: “A Universe from Nothing” by Lawrence Krauss, “Until the End of Time”, “The Elegant Universe” and “The Hidden Reality” by Brian Greene, “The Big Picture: On the Origins of Life, Meaning, and the Universe Itself and “From Eternity to Here: The Quest for the Ultimate Theory of Time” by Sean M. Carroll, “Origins: Fourteen Billion Years of Cosmic Evolution” by Neil deGrasse Tyson, , “To Explain the World: The Discovery of Modern Science” by Steven Weinberg, “Why Does E=mc2?” and “Wonders of the Universe” by Brian Cox, “Longitude” by Dava Sobel, “Cosmos” by Carl Sagan, and “The Grand Design” by Stephen Hawking.
“The Edge of Knowledge” renowned theoretical physicist and bestselling author Lawrence Krauss examines the threshold of the unknown and explores how far science has progressed. This stimulating 235-page book includes the following five chapters: 1. Time, 2. Space, 3. Matter, 4. Life, and 5. Consciousness.
Positives:
1. Well-written and well-researched book.
2. The fascinating topic of mysteries of the cosmos in the capable hands of Professor Krauss.
3. Krauss does a commendable effort of simplifying complex topics. His writing style is somewhat casual but he makes clear what we know versus what we don’t know. Each chapter begins with philosophical questions and quotes that are topic-appropriate followed by a stimulating discussion.
4. The concept of time. “Time and space are relative, and “now” only has an objective meaning for events that happen where you are located, so “now” is not a universal concept throughout the universe.”
5. Explains the key differences on when to apply Newtonian physics and not. “We now know that Newton’s law of gravity is not the correct theory to use when escape velocities approach the speed of light. Instead, we must resort to general relativity, which allows for the curvature of space as well as time dilation.”
6. Interesting facts throughout the book. “Since reaction rates increase exponentially with temperature, and temperature skyrockets as one approaches t=0, it is possible to estimate that more reactions occurred between particles in the first second of the history of the universe than will likely occur in the entire future history of the universe, even if that history is eternal! In this sense, we were born after almost all the good stuff happened.”
7. Understanding the importance of identifying the geometric pattern of space. “Namely, the ultimate future of the universe depends simply on whether the universe is open, closed, or flat, which is why determining which geometric pattern described our universe became the holy grail of cosmology.”
8. Discusses major findings in physics. “The Laser Interferometer Gravitational Wave (LIGO) observatory’s discovery of gravitational waves from colliding black holes on September 14, 2015, was a monumental achievement in physics, worthy of the 2017 Nobel Prize that was awarded to its developers.”
9. Discusses the main theories behind quantum gravity. “I consider string theory to be the leading candidate for a theory of quantum gravity, although that does not mean I think it is likely to be the correct theory.”
10. Discusses the biggest mystery in particle physics. “My favorite elementary particles in nature, neutrinos—ethereal particles released during nuclear reactions, whose interactions with normal matter are so weak that neutrinos streaming at us from the nuclear reactions inside the sun can go right through the earth without a single interaction—have a mass that is not predicted in the Standard Model, or even easily accommodated within it. Some new physics must be involved. We just don’t know what.”
11. The mystery of gravity. “Gravity stands out among the four known forces in nature because classical general relativity is incompatible with quantum mechanics.”
12. Throughout the book Krauss makes references to the giants of physics. “In 1929, the British theoretical physicist Paul Dirac figured out a way to unify quantum mechanics and special relativity, in turn producing a quantum theory of electromagnetism called quantum electrodynamics. It was a remarkable achievement that placed Dirac in the ranks of the greatest theoretical physicists of the twentieth century.”
13. Provides an outline of our quantum universe. “The fundamental quantity in quantum mechanics is the wavefunction of an object, which, succinctly, allows an exact prediction of the probability of measuring the object in any one of the allowed states it may be measured to be in, for all times.”
14. Describes science. “Science is about processes, about understanding dynamics—and that is what I want to focus on.”
15. The fascinating science of the origin of life. “While the details of the origin of life remain among the great unknowns of science, through a series of baby steps—interspersed with periodic giant leaps over the past fifty years—it is now not unreasonable to think that this mystery may be resolved in the coming decades.”
16. Is there life elsewhere in the universe? “Evidence of liquid water having flowed on its surface in the past, along with substantial evidence of water on or beneath its surface in places, has raised hopes of finding evidence for past or present life. Water is, after all, the source of life on earth.”
17. Explores consciousness. “There are now two ways of considering the role of consciousness in this picture. In the first, items in this workspace become conscious thoughts by virtue of being brought to the front layer of the monitor window—that is, being broadcast. In the second, all the windows are part of our consciousness.”
18. The evolution of language. “Chomsky has argued that language evolved as a part of neural circuitry that effectively generates thoughts, making modern cognition, reflection, and self-awareness possible. Internally generated thoughts can then sometimes be externalized via a sensory-motor medium and then used for communication.”
19. Describes the brain. “The brain is at the very least a distributed processing system, with multiple routes for information flow and processing, multiple centers, and many inputs for and alterations of cognitive states that we are not consciously aware of.”
20. Provocative statements. “As I have often said, not understanding something is not evidence for God or human frailty. It is just evidence of not understanding. And it should be an invitation to explore and learn.”
Negatives:
1. Regardless of the commendable effort to simplify such complex topics; many topics are beyond even the basic comprehension of the layperson. Quantum mechanics is not for the faint of heart.
2. There are better books covering some of the topics in more detail.
3. Lack of supplementary material.
In summary, this is a solid and stimulating book that explores the unknowns based on a solid foundation of science. Krauss covers five topics and provides readers a lot to digest. Each chapter begins with stimulating questions and topic-appropriate quotes followed by a narrative that pursue the answers. The book is brief but the discussion is substantive and Krauss succeeds in inspiring further pursuits. I recommend it.
Further recommendations: “A Universe from Nothing” by Lawrence Krauss, “Until the End of Time”, “The Elegant Universe” and “The Hidden Reality” by Brian Greene, “The Big Picture: On the Origins of Life, Meaning, and the Universe Itself and “From Eternity to Here: The Quest for the Ultimate Theory of Time” by Sean M. Carroll, “Origins: Fourteen Billion Years of Cosmic Evolution” by Neil deGrasse Tyson, , “To Explain the World: The Discovery of Modern Science” by Steven Weinberg, “Why Does E=mc2?” and “Wonders of the Universe” by Brian Cox, “Longitude” by Dava Sobel, “Cosmos” by Carl Sagan, and “The Grand Design” by Stephen Hawking.
October 6, 2023
This book is divided into chapters on Time, Space, Matter, Life, and Consciousness. I didn't find any new information in these chapters; the Matter chapter seemed directly lifted from a physics textbook. However, the author did play to his strengths here.
In my opinion, this is a standard book with typical content. Despite my admiration for Mr. Krauss's works, my personal liking for what he writes isn't the deciding factor for me. What keeps me engaged is my enthusiasm for the subject matter.
Would I recommend this book? No, unless you have a penchant for nerdiness.
In my opinion, this is a standard book with typical content. Despite my admiration for Mr. Krauss's works, my personal liking for what he writes isn't the deciding factor for me. What keeps me engaged is my enthusiasm for the subject matter.
Would I recommend this book? No, unless you have a penchant for nerdiness.
January 3, 2024
Good book but too complex for people without a physics degree. Could use some schematics or pictures to clarify some of the long and complicated sentences. Also, the English is pretty high level while this book will probably be read by a lot of people who are not native speakers. But I made it through and found a lot of insightful material.
May 11, 2024
During my high school days in India, we could find many Russian books in English on the market. Due to the political ties between our nations, they were highly subsidized and, therefore, very affordable. I was particularly attracted to the science books, many of which were written by famous Russian scientists for a younger audience. One such book was a high school textbook on Physics. I no longer recall the name of the book or the author, but I remember how well-written it was compared to the textbook that was prescribed by my school. What I found most remarkable, inspiring, and different was that each chapter ended with an open problem in that area of Physics. These are unsolved problems that a student at that level can appreciate. Unlike most other high school level books, where the author had the voice of an omniscient god, pretending they can answer any question, this author had the scientist's humility to expose what we do not know. This had a magical effect on my young mind, to be challenged and to know there are still many things we cannot understand and explain.
This book by Lawrence Krauss, one of the most well-known names in contemporary theoretical physics, attempts to do the same at a larger scale. It covers big ideas such as space, time, life, and consciousness, and takes us step by step to the frontier of these concepts, and then describes the known unknowns.
That is a daunting task because appreciation of these ideas requires a thorough knowledge of what has happened before. Modern theoretical physics, life science, or consciousness research are complex ideas, very often only possible to describe with a step-by-step build-up using advanced mathematics. This is why most popular-level physics books on contemporary physics become magical hocus pocus rather than truly explaining what they try to explain. The author here faced similar challenges and has done a reasonably good job. The portions on modern physics may still sound like a bit of magic, but I am not sure there is any way around that. Physics is no longer intuitive at extreme scales of space and time. They depart so far from what we experience at our human scale that there is no way to make them intuitively understandable. Still, they are equally difficult to understand intellectually without the mathematics involved.
Despite all these caveats, it is a wonderful read that will take the reader to the edge of known knowledge and make us see the vast chasm beyond the edge. It will probably make them sad to realize that our lives are finite, and we may not see the answers to many of these essential questions in our lifetime.
This book by Lawrence Krauss, one of the most well-known names in contemporary theoretical physics, attempts to do the same at a larger scale. It covers big ideas such as space, time, life, and consciousness, and takes us step by step to the frontier of these concepts, and then describes the known unknowns.
That is a daunting task because appreciation of these ideas requires a thorough knowledge of what has happened before. Modern theoretical physics, life science, or consciousness research are complex ideas, very often only possible to describe with a step-by-step build-up using advanced mathematics. This is why most popular-level physics books on contemporary physics become magical hocus pocus rather than truly explaining what they try to explain. The author here faced similar challenges and has done a reasonably good job. The portions on modern physics may still sound like a bit of magic, but I am not sure there is any way around that. Physics is no longer intuitive at extreme scales of space and time. They depart so far from what we experience at our human scale that there is no way to make them intuitively understandable. Still, they are equally difficult to understand intellectually without the mathematics involved.
Despite all these caveats, it is a wonderful read that will take the reader to the edge of known knowledge and make us see the vast chasm beyond the edge. It will probably make them sad to realize that our lives are finite, and we may not see the answers to many of these essential questions in our lifetime.
September 7, 2023
I like this this book. I like the idea of this book, and I like the sentiments and logic. Krauss wants to tell us what are the limits of human knowledge in a variety of scientific fields. He then uses this discussion as a way to delineate various possible theories about the unknown and why they may or may not be true. Try to frame possible questions. Are these even the right questions to ask? Take people to the edge and show them what may lay beyond. Excellent. However, I found the execution sometimes lacking.
There are five chapters in the book titled Time, Space, Matter, Life, and Consciousness. They are not all at the same level of difficulty. In order of difficulty, from easiest to most difficult, I would say it goes Consciousness, Life, Time, Space, Matter. To give examples of the questions he asks: What is consciousness? How did life form? What are the building blocks of matter? Is the universe infinite? What happened at the Big Bang? Krauss explains what physicists think they know, and then what hypotheses have been advanced to try to advance our knowledge beyond that, and what evidence, if any, exists to support them.
This book is meant for the general reader, but I would say it is for an highly-educated general reader. I struggled to understand large parts of it, had to read sentences and paragraphs two or three times, and still I did not get it all. For a more friendly explanation of some of the same phenomenon I would recommend “The Fabric of the Cosmos.: by Brian Greene, If I hadn’t read that book first, I don’t know what I would have got from the first three chapters of this book. For example, Krauss wrote about the physicist Roger Penrose’s idea of a past and present “light cone” that contain all the past and present light signals that we could ever possibly receive or communicate, and how the future light cone will get bent in towards the event horizon of a black hole as I approach it. That is fine, but Greene provided diagrams in his book and I was thinking about those when I read this one. Krauss tends to get to the point of what he wants to say and just assumes the reader will keep up. Sometimes I couldn’t. This book could have been a little longer for we normal people. Maybe some friendly illustrations.
I get Krauss’ dedication Welcome back to Canada, and I hope that, in Prince Edward Island, you have found your refuge from the culture wars. I like your podcasts.
There are five chapters in the book titled Time, Space, Matter, Life, and Consciousness. They are not all at the same level of difficulty. In order of difficulty, from easiest to most difficult, I would say it goes Consciousness, Life, Time, Space, Matter. To give examples of the questions he asks: What is consciousness? How did life form? What are the building blocks of matter? Is the universe infinite? What happened at the Big Bang? Krauss explains what physicists think they know, and then what hypotheses have been advanced to try to advance our knowledge beyond that, and what evidence, if any, exists to support them.
This book is meant for the general reader, but I would say it is for an highly-educated general reader. I struggled to understand large parts of it, had to read sentences and paragraphs two or three times, and still I did not get it all. For a more friendly explanation of some of the same phenomenon I would recommend “The Fabric of the Cosmos.: by Brian Greene, If I hadn’t read that book first, I don’t know what I would have got from the first three chapters of this book. For example, Krauss wrote about the physicist Roger Penrose’s idea of a past and present “light cone” that contain all the past and present light signals that we could ever possibly receive or communicate, and how the future light cone will get bent in towards the event horizon of a black hole as I approach it. That is fine, but Greene provided diagrams in his book and I was thinking about those when I read this one. Krauss tends to get to the point of what he wants to say and just assumes the reader will keep up. Sometimes I couldn’t. This book could have been a little longer for we normal people. Maybe some friendly illustrations.
I get Krauss’ dedication Welcome back to Canada, and I hope that, in Prince Edward Island, you have found your refuge from the culture wars. I like your podcasts.
October 14, 2023
This book is not for beginners. If you are looking for a basic overview of current scientific dilemmas then, frankly, others have done a more entertaining job of it. I’d look at Bill Bryson or Michio Kaku. For one thing, this is all text; something Krauss churned out on his laptop during Covid downtime. Yes, graphs and illustrations take more time and money in preparing a book, but for the beginner some sort of visual aid is going to be very helpful. I’d say this is more of an intermediate level mediation on “the state of things.”
For me, portions of the book were tedious because this material has already been covered so many times, like the train station analogy to explain Einstein’s relativity, or the concept of infinity explained with the Hilbert’s Hotel analogy. But in the in-between spaces of mandatory popularization script, where Krauss talks about what he really wants to talk about, I found much to enjoy, and a few things that clarified my own thinking on certain matters.
Firstly, I now have a greater appreciation for the contributions of Alan Guth, whose quiet manner has always seemed to place him in the shadows of more forceful personalities such as Max Tegmark or even Sir Roger Penrose. In fact, I find that Guth’s theories align very closely with my own thinking. Second, I was really awakened to the semantic subterfuge used by quantum theory advocates in describing non-deterministic superposition , superluminal interaction, and the conscious observer phenomenon to explain how we can manipulate matter and reality if we just think hard enough. I’d say this important clarification alone was probably worth the time and money to read this book. (See pages 114-117.)
You can also watch the 46-minute lecture online, or see the podcast conversation with Sabine Hossenfelder about the book, but, of course, the book itself contains much more detail. If I had only watched the online content I would have missed the most important takeaways that this book offers. Still, the online content is a nice supplement, and Lawrence Krauss is in some ways a more effective communicator in person than in his writings.
For me, portions of the book were tedious because this material has already been covered so many times, like the train station analogy to explain Einstein’s relativity, or the concept of infinity explained with the Hilbert’s Hotel analogy. But in the in-between spaces of mandatory popularization script, where Krauss talks about what he really wants to talk about, I found much to enjoy, and a few things that clarified my own thinking on certain matters.
Firstly, I now have a greater appreciation for the contributions of Alan Guth, whose quiet manner has always seemed to place him in the shadows of more forceful personalities such as Max Tegmark or even Sir Roger Penrose. In fact, I find that Guth’s theories align very closely with my own thinking. Second, I was really awakened to the semantic subterfuge used by quantum theory advocates in describing non-deterministic superposition , superluminal interaction, and the conscious observer phenomenon to explain how we can manipulate matter and reality if we just think hard enough. I’d say this important clarification alone was probably worth the time and money to read this book. (See pages 114-117.)
You can also watch the 46-minute lecture online, or see the podcast conversation with Sabine Hossenfelder about the book, but, of course, the book itself contains much more detail. If I had only watched the online content I would have missed the most important takeaways that this book offers. Still, the online content is a nice supplement, and Lawrence Krauss is in some ways a more effective communicator in person than in his writings.
July 7, 2023
Not being a physicist, let alone an astrophysicist, I can't assess the merit or otherwise of the various hypotheses that Krauss advances to explain the nature of time, space, matter, life and consciousness. My comments are those of a lay person who is fascinated by the subjects but not schooled in them. Krauss canvasses many theories, including those of his peers, and I detected a degree of competitiveness permeating through his analyses. ( A useful insight into academia, perhaps.) Unfortunately he does not write well for the layman, becoming impenetrable in parts, as if looking over his shoulder at his fellow theoretical physicists and afraid of being accused of being too popular. They say that the essence of good science is to postulate a theory and then try and prove it wrong. What this book proves is that there are still an infinite number of theories around these foundational subjects and anyone's guess is as good as another. As job sectors go, these theoretical physicists will never be out of work.
July 12, 2023
A Book about The Known Unknowns!
Time, Space, Matter, Life, & Consciousness. These are the Concepts Krauss addresses in this work. In my experience Krauss can be a very difficult read. His brilliance is unquestionable but when he delves into the Mysteries of Physics and The Cosmos he often loses me. The first couple of Topics pretty much did this again.
Things got better in the section on Matter but again, whenever he mentioned Quantum-anything, I broke out in a cold sweat. I did though very much understand and enjoy most of the Life and Consciousness chapters.
He expands on much of Damasio’s theories of the operation of The Brain and Consciousness that I have been impressed by and did a great job of explaining those issues quite clearly.
This was a very worthwhile experience. Any lack of clarity lies in the Brain of this Reader!
Four Stars. ****
Time, Space, Matter, Life, & Consciousness. These are the Concepts Krauss addresses in this work. In my experience Krauss can be a very difficult read. His brilliance is unquestionable but when he delves into the Mysteries of Physics and The Cosmos he often loses me. The first couple of Topics pretty much did this again.
Things got better in the section on Matter but again, whenever he mentioned Quantum-anything, I broke out in a cold sweat. I did though very much understand and enjoy most of the Life and Consciousness chapters.
He expands on much of Damasio’s theories of the operation of The Brain and Consciousness that I have been impressed by and did a great job of explaining those issues quite clearly.
This was a very worthwhile experience. Any lack of clarity lies in the Brain of this Reader!
Four Stars. ****
July 21, 2023
"The Edge of Knowledge" is a fun book of casual physics. None of Krauss's descriptions of time, space, matter, life, and consciousness are difficult to understand. (His section on matter is probably the most abstruse but even that chapter doesn't really tax the intellect.) The book will give readers a good understanding of some of the unanswered questions currently vexing scientists. The chapters on life and consciousness are the most speculative but interesting nonetheless. I feel like the content of this book is very similar to topics discussed in Krauss's other work. In that regard, this book felt like a repeat. I also found many typos in my version of the book (Kindle). Krauss would do well to hire a better copy editor for any of his future books. Recommended particularly if you've never read any of his other books.
November 25, 2023
Why physicist write the SAME BOOK every day?
This is another book that says: "we don´t know this", "This can be, but cannot be", "I vouche for this, but Dr. X vouche for that, and I don´t concur with him"...
We are kinda f*** in modern physics atm. We have technical limits, we have theoric limits, we have methodological limits and, probably, we have epistemological limits...
Every physicist should start any argument with "ATM, we/I think, based on our best theories...". They usually say THIS, without conditionants...
Not a bad book, just the same book.
This is another book that says: "we don´t know this", "This can be, but cannot be", "I vouche for this, but Dr. X vouche for that, and I don´t concur with him"...
We are kinda f*** in modern physics atm. We have technical limits, we have theoric limits, we have methodological limits and, probably, we have epistemological limits...
Every physicist should start any argument with "ATM, we/I think, based on our best theories...". They usually say THIS, without conditionants...
Not a bad book, just the same book.
September 7, 2023
If you know any young person interested in the sciences, this is the book for them. Krauss outlines all of the mysteries of time, space, matter, life and consciousness, yet to be solved.
As someone with no science background, I found the book accessible (although I admit the chapter on matter I need to read once more) and exciting. Great man. I love his podcast, and now want to go read all of his previous books.
As someone with no science background, I found the book accessible (although I admit the chapter on matter I need to read once more) and exciting. Great man. I love his podcast, and now want to go read all of his previous books.
February 28, 2024
fantastic exposition of this scientist’s wealth of knowledge and indeed of the current state of science
Krause has a produced a very readable book for many with a moderate science background that outlines some of the biggest scientific challenges as was the greatest achievements. Hopefully it will influence some nascent scientist to answer and pursue some of these questions as he says in the epilogue.
Krause has a produced a very readable book for many with a moderate science background that outlines some of the biggest scientific challenges as was the greatest achievements. Hopefully it will influence some nascent scientist to answer and pursue some of these questions as he says in the epilogue.
April 2, 2024
A simple explanation of the things we yet do not know and understand. Krauss makes no pretentions while he explains in simple prose the issues at hand. A great read for anyone interested in science and where it is currently heading. To those who don't like science or have any negative feelings towards it for whatever reason, it is also a good book to read because they would know that science is an open endeavor and enterprise that invites everyone at the table.
October 30, 2023
This book is just incredible. Hands down one of the best books I've ever read! It is insanely insightful. Every single topic in this book has something for everyone. It goes without saying, if you really want to understand more about reality and the most complex processes in nature, then this is a MUST read!
January 18, 2024
สุดเขตแดนแห่งความรู้ ปริศนาที่ยังไขไม่ได้ของจักรวาล สิ่งที่มนุษย์รู้ว่าไม่รู้ เอกภพของเราเริ่มต้นอย่างไร?, เอกภพจะจบลงอย่างไร? สิ่งมีชีวิตบนโลกเกิดขึ้นมาได้อย่างไร? จิตสำนึก (consciousness) คืออะไร? คำถามเหล่านี้เป็นสิ่งที่วิทยาศาสตร์กำลังหาคำตอบ ในมุมมองของนักฟิสิกส์ ไม่ค่อยละเอียดเท่าไรและอธิบายแบบไปเร็วมาก บางเรื่องเคยอ่านที่อธิบายได้ดีกว่านี้
July 10, 2023
Good but not as good as it could be.
I own several of his books and find this one too be not up to his writing abilities. Perhaps he's writing too many articles so he doesn't have time. The first 3 sections are a mostly good read.
I own several of his books and find this one too be not up to his writing abilities. Perhaps he's writing too many articles so he doesn't have time. The first 3 sections are a mostly good read.
August 3, 2023
Surface level popsci, the physics topics that Krauss knows are covered well enough but not better than any other book in this genre. The topics he doesn't know are skimmed over like you'd hear on a podcast.
January 21, 2024
I liked the last chapter about consciousness, but found the sections about time and space pretty impenetrable. Not a primer for the layperson; the author assumes his reader has some knowledge of astrophysics.
September 18, 2024
I did not finish this book. Much of the content is a repeat of Krauss' earlier book "A universe from nothing", and discusses complicated physics at a high level. The writing style was also quite boring and I didn't find it captivating or engaging.
Displaying 1 - 30 of 35 reviews