Three Roads to Quantum Gravity Read Online Free
Author: Lee Smolin
gravity has not come out of the head of two or three neo-Einsteins. Rather, it is the result of several decades of intense effort by a large and growing community of scientists. In most cases to name only a few people would be a disservice to both the community of scientists and to the reader, as it would reinforce the myth that science is done by a few great individuals in isolation. To come anywhere near the truth, even about a small field like quantum gravity, one has to describe the contributions of scores of people. There are many more people to name than could be kept track of by the reader encountering these ideas for the first time.
For a few episodes with which I was involved enough to be confident of knowing what happened, I have told the stories of how the discoveries were made. Because people are most interesting when one tells the truth about them, in these cases I am happy to introduce some very human stories to illustrate how science actually gets done. Otherwise I have stayed away from telling the stories of who did what, for I would inevitably have got some of it wrong, in spite of having been a close observer of the subject for the last two decades.
In taking the liberty of telling a few stories I also take a risk, which is that the reader will get the impression that I believe my own work to be more important than the work of other people in the field. This is not true. Of course, I do believe in the approach I pursue in my own research, otherwise I would not have a point of view worth forming a book around. But I believe that I am also in a position to make a fair appraisal of the strengths and weaknesses of all the different approaches, not only those to which I’ve contributed. Above all else, I feel very privileged to be part of the community of people working on quantum gravity. If I were a real writer, skilled in the art of conveying character, I would like nothing better than to describe some of the people in this world I most admire, from whom I continue to learn, every chance I get. But given my limited skills I shall stick to a few stories about people and incidents I know very well.
When our task is done, someone will write a good history of the search for quantum gravity. Whether this will be in a few years, as I believe, or in many decades, as some of my more pessimistic colleagues expect, it will be a story in which the best human virtues, of courage, wisdom and vision, are mixed with the most ordinary sort of primate behaviour, expressed through the rituals of academic politics. I hope that story will be written in a style that celebrates both sides of our very human occupation.
Each of the following chapters is devoted to one step in our search for the quantum theory of gravity. We begin with four basic principles that determine how we approach our enquiry into the nature of space, time and the cosmos. These make up the first part, called ‘Points of departure’. With this preparation we turn to the second part, ‘What we have learned’, in which I shall describe the main conclusions that have so far been arrived at on the three roads to quantum gravity. These combine to give us a picture of what the world is like on the smallest possible scales of space and time. From there we turn to the last part, a tour of ‘The present frontiers’ of the subject. We shall introduce a new principle, called the holographic principle, which may very well be the fundamental principle of quantum gravity. The next chapter is a discussion of how the different approaches to quantum gravity may be coming together into one theory which seems to have the possibility of answering, at least for the foreseeable future, our questions about the nature of space and time. I end with a reflection on the question of how the universe chose the laws of nature.
We begin at the beginning, with the first principle.
I
POINTS OF DEPARTURE
CHAPTER 1
THERE IS NOTHING OUTSIDE THE UNIVERSE
W e humans are the species
For a few episodes with which I was involved enough to be confident of knowing what happened, I have told the stories of how the discoveries were made. Because people are most interesting when one tells the truth about them, in these cases I am happy to introduce some very human stories to illustrate how science actually gets done. Otherwise I have stayed away from telling the stories of who did what, for I would inevitably have got some of it wrong, in spite of having been a close observer of the subject for the last two decades.
In taking the liberty of telling a few stories I also take a risk, which is that the reader will get the impression that I believe my own work to be more important than the work of other people in the field. This is not true. Of course, I do believe in the approach I pursue in my own research, otherwise I would not have a point of view worth forming a book around. But I believe that I am also in a position to make a fair appraisal of the strengths and weaknesses of all the different approaches, not only those to which I’ve contributed. Above all else, I feel very privileged to be part of the community of people working on quantum gravity. If I were a real writer, skilled in the art of conveying character, I would like nothing better than to describe some of the people in this world I most admire, from whom I continue to learn, every chance I get. But given my limited skills I shall stick to a few stories about people and incidents I know very well.
When our task is done, someone will write a good history of the search for quantum gravity. Whether this will be in a few years, as I believe, or in many decades, as some of my more pessimistic colleagues expect, it will be a story in which the best human virtues, of courage, wisdom and vision, are mixed with the most ordinary sort of primate behaviour, expressed through the rituals of academic politics. I hope that story will be written in a style that celebrates both sides of our very human occupation.
Each of the following chapters is devoted to one step in our search for the quantum theory of gravity. We begin with four basic principles that determine how we approach our enquiry into the nature of space, time and the cosmos. These make up the first part, called ‘Points of departure’. With this preparation we turn to the second part, ‘What we have learned’, in which I shall describe the main conclusions that have so far been arrived at on the three roads to quantum gravity. These combine to give us a picture of what the world is like on the smallest possible scales of space and time. From there we turn to the last part, a tour of ‘The present frontiers’ of the subject. We shall introduce a new principle, called the holographic principle, which may very well be the fundamental principle of quantum gravity. The next chapter is a discussion of how the different approaches to quantum gravity may be coming together into one theory which seems to have the possibility of answering, at least for the foreseeable future, our questions about the nature of space and time. I end with a reflection on the question of how the universe chose the laws of nature.
We begin at the beginning, with the first principle.
I
POINTS OF DEPARTURE
CHAPTER 1
THERE IS NOTHING OUTSIDE THE UNIVERSE
W e humans are the species
Readers choose
Krissie LaBaye
Philip Hinchcliffe
Graeme Kent
Gertrude Chandler Warner
J.M. Gregson
Gramps Doodlebug
Kathy Bennett
Brian Herbert
Niobia Bryant
Penelope Mortimer