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le 19 décembre 2009
Ce livre même lu en anglais par un jeune de 14 ans comme moi avec un petit dico à portée de main est une vrai mine d'informations sans formules complexes . Vraiment un livre à lire pour savoir ce qui se passe dans l'espace !
0Commentaire| 7 personnes ont trouvé cela utile. Ce commentaire vous a-t-il été utile ?OuiNonSignaler un abus
le 4 octobre 2015
You’re bound to ask me: Why do you bother to read and analyze a book that is nearly 30 years old, and that is ancient in modern scientific terms? Since then the term “singularity” has been made extremely popular by people like Ray Kurzweil who are programming in their heads a new singularity around 2050 when machines will become more intelligent than man, and for him that is programmed in the very nature and essence of the universe. In front of this imminent prediction Hawking sounds a little bit passé if not maybe even déjà-vu. The worst part of it is that Hawking is totally harmless in front of such very commercially minded and aggressive theories because he NEVER asks the proper question which is: What is human intelligence? How did it develop? Is it still able to develop? What makes man an intelligent being?

To even imagine we can discuss such a book we have to start from the conclusion because the whole book is a systematic exploration of various theories under various angles and merging procedures always coming to the final idea that it may work but may just the same not work. Page 167 Hawking says very wisely the fundamental truth in science: “Theories can’t be proved.” And he spent a lot of pages explaining that theories are nothing but constructs, human constructs trying to understand the world. These theories he explains over and over again are models of the world and not the world itself. Page 165 he asks: “Are we perhaps just chasing a mirage?” In fact he uses the wrong word. We are chasing “models” which are pure human mental constructs. And he knows it since page 9 he said:

“A theory is a good theory if it satisfies two requirements: It must accurately describe a large class of observations on the basis of a model that contains only a few arbitrary elements, and it must make definite predictions about the results of future observations.”

It seems coherent except that he forgets a third dimension of a theory that deals with any phenomenon that develops in time – wrong word – that has a duration since time is a human invention since clocks do not grow on trees. A good theory has to explain with its own model how the phenomenon has reached the point at which we observe it. Why did he forget this dimension on which he insists all along in the book? He is the only one who is able to answer this question but I think it has to do with his obsession with time not realizing that time as such does not exist in the cosmos. In the cosmos there is only duration because time requires some measuring device and thus some conscious intelligence that proposes a model and a theory to explain what every item of whatever nature in the cosmos experiences with or without any consciousness of it, precisely duration. Augustine had it right when he said that time as a beginning and an end (the famous alpha and omega, but also the famous "I am the Alpha and the Omega," says the Lord God, "who is, and who was, and who is to come, the Almighty." Revelation 1:8) and that it was invented by God. In modern terms time has been devised and then measured and finally conceptualized by man and thus it has a beginning and an end but duration does not. The universe did not wait for man to go on existing and evolving without the concept of time but with the experience of duration, mostly unconscious because the universe as such does not have a mind and consciousness.

The three sides of the theoretical mirage
Then if you forget that theories cannot be proved and are nothing but models, hence intelligent figments of man’s mind and imagination you can come to the slicing up of the “mirage” in three portions like page 166:

“. . . only three possibilities:
1) There really is a complete unified theory, which we will someday discover if we are smart enough.
2) There is no ultimate theory of the universe, just an infinite sequence of theories that describe the universe more and more accurately.
3) There is no theory of the universe; events cannot be predicted beyond a certain extent but occur in a random and arbitrary manner.”

The first hypothesis is typical of Hawking’s thinking. He thinks theories that cannot be proved, though by the way they can be disproved, falsified by plain experience like sailing around the world against the plate-like theory of the earth; theories that are nothing but the products of man’s intelligence, mind and imagination, though we should add at the very beginning observation (and that is not yet enough); he thinks that theories are “discovered” which they cannot be since they do not exist outside our own mental consciousness as constructs of our own mind. In fact any theory is the result of a long process that Bertrand Russell started analyzing a long time ago in his lectures on the mind. Man senses first with his sense organs (pure nervous influx caused by the “contact” with what is observed). Then man perceives when the brain receives these sensations and sorts them out to make them analyzable by the brain itself, a sort of formatting necessary for further work. Note all animals do that. And thus from sensations we shift to perceptions. But then the brain has to put a tag on it and store it in some memory and that is the main difference between man and all other species: the perception is going to be tagged with a “name” that can be uttered because man has the potential of a fully articulated (three articulations) language that he has to develop vowel after vowel, consonant after consonant, referring item after referring item, meaningful item after meaningful item, morphological procedure after morphological procedure, syntactic structure after syntactic structure, and the whole thing to produce and transmit meaning in a complete act of communication. And that’s only half the procedure from observation to theory.

Man”s conceptual power
The second half is entirely based on that language that Homo Sapiens must have taken 50,000 years at least to develop to a certain level of complexity on the basis of the communicational situation that was his at the time – and still is today – and that was and still is the matrix of the whole linguistic ability and all semantic, syntactic and morphological dimensions of language. On the basis of his observation man has to experiment, then to speculate on the further observations after that experimentation, and finally to conceptualize, and that’s where the theories come into being. The first theory will be supernatural of some sort, including God of course and the divine. The next theory will be all kinds of technologies and techniques man developed to increase his means of survival and subsistence, and that leads to hunting techniques, tool and weapon production, the cultivation of the natural garden to enhance and improve the gathering of plants, fruit, roots, whatever, and that cultivation of the natural garden which is more husbandry than agriculture will lead to agriculture. Imagine the thousands of theories necessary to develop that practice and each theory will survive as long as it is effective, not disproved by experiments and practices. The last level of theorization is philosophy, maybe as a first step, then science, and science developed along with the intelligence and language of humanity as a whole and within this humanity the language of those who were the “intellectuals,” the “language specialists,” the “priests,” the “scientists” and “technicians.”

Hawking is so far from all that. His first possibility is absurd because we will never have a total knowledge of the cosmos and the world we are living in, particularly because we will never know why and what for we are here. The second possibility is the only acceptable: we are scientifically tinkering about with our mind that enables us to sense, perceive, identify, experiment, speculate and conceptualize and we will never reach a complete and unified knowledge especially since we only invent answers to the basic questions: Why are we here? What are we here for? Where are we coming from (though we know it: from Africa)? But where is this universe, cosmos coming from? And that we do not know. So we invented theories to answer these questions: God, supernatural forces, extraterrestrials, and of course science, pretty soon if we follow Ray Kurzweil we will descend from the machines we will have invented and that will self develop then.

The third possibility is even worse since this time it plainly negates man’s power to sense, perceive, identify, experiment, speculate and conceptualize since everything is plain random, arbitrary, accidental, haphazard, etc. At this level it is the pure ignorance of what is called evolution which is, based on Darwin’s approach, first the absolutely haphazard mutations WITHIN THE LIMITS OF WHAT ALREADY EXISTS AND IN WHICH THESE MUTATIONS APPEAR but with natural selection afterwards that only retains what enables the considered evolving beings to better survive in the environment that is theirs, and that includes the planets, the stars, the constellations, the galaxies, the cosmos in one word which its own direct environment though we have to think there is something beyond and we don’t know what it is. That means the randomness of this possibility is very well guided and then selected by what already exists. And Hawking knows that perfectly well when he says: “We have, as yet, had little success in predicting human behavior from mathematical equations!” (p. 168) and yet at once he falls back into his first possibility seen as man’s target: “Our goal is a complete understanding [his emphasis] of the events around us, and of our existence.” (p. 169) That’s just his main misunderstanding: there cannot be ANY COMPLETE understanding because our models and theories are not the world but only some mental constructs that represent what we understand of the world, and some of that understanding might be completely wrong, but all of it cannot be complete at all. Vanitas vanitatum , omnis vanitas.

The theory of the Big Bang
That’s where I would like to come to the theory of the Big Bang. He summarizes the problem very well in his conclusion:

“According to the general theory of relativity, there must have been a state of infinite density in the past, the big bang, which would have been an effective beginning of time. Similarly, if the whole universe recollapsed, there must be another state of infinite density in the future, the big crunch, which would be an end of time. . . When we combine quantum mechanics with general relativity, there seems to be a new possibility that did not arise before: that space and time together might form a finite, four-dimensional space without singularities or boundaries, like the surface of the earth but with more dimensions. . . But if the universe is completely self contained, with no singularities or boundaries, and completely described by a unified theory, that has profound implications for the role of God as Creator.” (p. 173-174)

There are two elements that bother me.

The first one is the very concept of a beginning and an end without telling me what the matter or antimatter, the extremely dense state of the something that is going to go big bang is and where it comes from. By setting an origin point, and what’s more an end point, we just push the question of where it all comes from slightly further, in fact completely out of the picture and that is the perfect rewriting of the most prodigious invention of man: the divine dimension of the world. There is not one culture that we know, in the past or the present that has not produced in a way or another the concept of some creating and creative force. The concept of creation is in itself a human view. But the second hypothesis proposed by Hawking of a completely self-contained universe is just as much unsatisfactory as the first one. If it is self-contained it is contained in itself so what is outside? Maybe it does not have a beginning and an end but what is beyond the container of this self-contained universe? And anyway where does it come from? But here Hawking reveals his real problem. He does not seem to be able to survive in his scientific world without constantly referring to God. There is not one chapter in which he does not come back to God. And yet he knows that obsession is an escape from the impossibility to know, to explain when he says: “Or does it need a creator, and, if so, does he have any other effect on the universe? And who created him?” (p. 174)

Then we have to dismiss this false question since it is a question that has no answer. In Theravada Buddhism it is reported that Buddha when asked if he believed in a God who would have created the world, he would have answered: “If so who created that God?” This line of questioning and reasoning is childish. We do not have to ask the question of who created what. It is a question of belief and faith and if that gives one some balance and energy to cope with the unanswerable question that’s fine and should not be even questioned. If we prefer accepting that the question of the “why” as Hawking says, the question of “what for” and “what from” in this order or the reverse as I would prefer to say, has no answer and we can live with that, that’s fine and should not be questioned because it is belief, faith, epiphany, peace of mind. There is no contradiction between this peace of mind that comes to terms with an unanswerable question by accepting its unanswerability on the one Hand, and the peace of mind that comes from the answer that it was created by some supernatural power, called God or whatever, and for the purpose of building a harmonious loving society that will come to an end in some apocalyptic singularity on the other hand.

The retrospective method
My last remark has to do with the retrospective method used by the Big Bang theorists. From what we know today which might be about the state of the universe that could go back millions of light-years, observed from the Earth positioned as central, which it is as an observation post but only for its observation not necessarily for the universe, these theorists draw conclusion about the very distant past of the origin of this universe. The origin can only ne stated as the retrospective result of a modern theory. Mathematically the general relativity theory comes down to one point of origin of it all. The Big Bang has not yet been proved and I just wonder how it could be proved by mathematics. It is deducted from one theory – and not the other or others – by the inner mathematics of that theory, which is at least mathematically circular, but we cannot observe any real fact that tells us this is the Big Bang.

In my field of science, linguistics, and phylogenic linguistics if you please, we have the same problem. For a long time the question of the origin of language was banned by the Paris School of Linguistics, then Greenberg’s work was negated and rejected though it was quite accurate, then Chomsky invented the innate black box that contained the whole Universal Grammar as a good way to pretend language was given ready made to man by his genes which were nothing but a substitute for God. We finally admit that the whole humanity (Homo Sapiens) evolved from anterior hominins in Africa and that the whole of humanity, except of course in black Africa, moved out of that section of Africa that was the nest (and maybe the nests) of Homo Sapiens, first to northern Africa, then via the Arabian Peninsula southern corridor to the whole world. That implies these Homo Sapiens who were moving out of Africa had languages. Then what is the phylogeny of language from zero, though Homo Sapiens inherited communicational means from the Hominins and even the Hominids they descended from, to today’s languages? But the most irritating approach is the restrospective Proto Indo-European theory. The point here is not whether there was or was not a Proto-Indo-European but the point is that those who –among others in Cambridge – advocate this procedure forget to ask a simple question when they situate this birth in the European plains north of the Black Sea. They forget to ask two simple questions: Where did these men come from? And What language or languages did they speak before? I will not insist on the highly unpronounceable nature of this Proto Indo European language, but I will insist on what Darwin said: nothing exists that does not descend from something before. And any mutation appears within the context of what existed before that mutation and that mutation will only survive by natural selection which means better survival for the concerned species within the natural conditions in which they live.

Conclusion
My experience in my scientific field makes me very critical of any retrospective procedure that does not descend things from what existed before but ascends the time line to some fictitious original place and time and state. By ascending the time line you ALWAYS project onto the past what you have in the present. We know the absurdity of the first name of Indo-European languages that were called Indo-Germanic languages/. We know the absurdity of considering Indo-European languages descend from Sanskrit, though both Indo-European languages and Indo-Aryan languages (Sanskrit is within this last branch) are the two branches of a common linguistic community that was living somewhere on the Iranian plateau and in Mesopotamia and arrived there around 50,000 years ago, finding already there the agglutinative Turkic languages that arrived a little bit earlier and move to Europe around 50,000 years ago to become the Old Europeans, Cro-Magnon and the Gravettians among others. And yet they all had come from Africa and these two vast, Turkic and Indo-European-Indo-Aryan families of languages were both of the third articulation migration(s). And that fact cannot be explained otherwise than by making them leave Africa at a certain phylogenic moment of the evolution of language in Africa itself.

That said, this book is a challenging book though vastly outmoded by science itself. But a challenge is a challenge and every student or person who pretend to have some scientific culture or practice should read it and ponder on it. What I have said is nothing but a few foolish remarks and a lot more should be said, but it would all go the same way. Man’s intelligence is evolving and the level of scientific knowledge humanity reaches in time represents a level of development of this intelligence and a potential for further development of this intelligence which is not innate but constructed in the mind along the line I have explained: sense-perceive-identify-experiment-speculate-conceptualize. Then as you can see a philosopher could both agree and disagree with Wittgenstein when he says “The sole remaining task for philosophy is the analysis of language.” Agree because that’s true. Philosophers can always spend there time discussion religion, art, culture, civilization and a few more humanities that all exist for the philosopher in some language or linguistic expression. Disagree because this language opens up onto man’s intelligence, man’s mind and without that language there would be no mathematics, chemistry or physics and a few other sciences like computer science.

Dr Jacques COULARDEAU
0Commentaire| 2 personnes ont trouvé cela utile. Ce commentaire vous a-t-il été utile ?OuiNonSignaler un abus
le 9 octobre 2002
As we are living in this beautiful scientific era, we should get the most of the what human brain has come up with over thousands of years !
In his best seller, Pr. Hawking gives a historical approach to the way prominent scientists describe the universe. From Ptolome until the beginning of this century, many theories have been competing to find the right laws that govern the solar system and the universe.
In his book, the author in his wheelchair, describes in an easy way the recent theories explaining the way the universe was born and the way it is growing. From quarks to black holes and from the big bang to the big crunch, the author takes us to a trip in time to elucidate the secrets of this 'strange and beautiful' evolving universe.
It is easy to understand, no mathematical background required, so every one is invited to enjoy the knowledge.
0Commentaire| 4 personnes ont trouvé cela utile. Ce commentaire vous a-t-il été utile ?OuiNonSignaler un abus
The mark of a true educator, which Stephen Hawking certainly is, is that he would take time (very valuable time, in his case) away from research and contemplation of the great mysteries of the universe to write a piece that would serve to help explain to the greater number of less-scientifically-adept persons the fruits and implications of modern scientific research from the cutting edge of physics. Hawking is ranked in popular and scientific thinking on a par with Einstein, and has motor neuron disability that severely restricts his ability to move, even to type or write, so, when he takes time to write something for general consumption, it is probably going to be worthwhile. And indeed, this is.
'Someone told me that each equation I included in the book would halve sales. I therefore resolved not to have any equations at all. In the end, however, I did put in one equation, Einstein's famous equation. I hope that this will not scare off half of my potential readers.'
Hawking begins by exploring the large scale structure of the universe (time being part of the `fabric' of the universe, in spacetime), the connections of space and time as a relatively new concept in thinking of the universe, and the way the universe `acts' (cosmological dynamics). From there, he explores the universe at a very basic level, as elementary particles and forces of nature, introducing quarks.
'There are a number of different varieties of quarks: there are thought to be at least six "flavours", which we call up, down, strange, charmed, bottom and top. Each flavour comes in three "colours", red, green and blue. ...We now know that neither the atoms nor the protons and neutrons within them are indivisible. So the question is: What are the truly elementary particles, the basic building blocks from which everything is made?'
From this discussion Hawking proceeds to black holes (and the fact that they aren't so black and permanent as popular belief holds them to be), which circles back around to the origin and destiny of the universe (which relates back to the large-scale structure), which ultimately brings us to time. This is where things begin to get interesting.
'When one tried to unify gravity with quantum mechanics, one had to introduce the idea of "imaginary" time. Imaginary time is indistinguishable from directions in space. If one can go north, one can turn around and head south; equally, if one can go forward in imaginary time, one ought to be able to turn around and go backward.'
Hawking explains variations of the thermodynamic, psychological and cosmological laws that regulate the direction of time's arrow, which, despite the theoretical flexibility of time with regard to scientific principles, always apparently goes in one direction.
Finally, Hawking explores the most current topic in theoretical physics: unification theories, which may or may not be a wild goose on the loose. Hawking also explores what such a grand unified theory (also called sometimes the `theory of everything') would mean, and what it wouldn't mean. But Hawking assures us that the quest for understanding is worthwhile even it won't be the final word on everything.
0Commentaire| Une personne a trouvé cela utile. Ce commentaire vous a-t-il été utile ?OuiNonSignaler un abus
The mark of a true educator, which Stephen Hawking certainly is, is that he would take time (very valuable time, in his case) away from research and contemplation of the great mysteries of the universe to write a piece that would serve to help explain to the greater number of less-scientifically-adept persons the fruits and implications of modern scientific research from the cutting edge of physics. Hawking is ranked in popular and scientific thinking on a par with Einstein, and has motor neuron disability that severely restricts his ability to move, even to type or write, so, when he takes time to write something for general consumption, it is probably going to be worthwhile. And indeed, this is.
'Someone told me that each equation I included in the book would halve sales. I therefore resolved not to have any equations at all. In the end, however, I did put in one equation, Einstein's famous equation. I hope that this will not scare off half of my potential readers.'
Hawking begins by exploring the large scale structure of the universe (time being part of the `fabric' of the universe, in spacetime), the connections of space and time as a relatively new concept in thinking of the universe, and the way the universe `acts' (cosmological dynamics). From there, he explores the universe at a very basic level, as elementary particles and forces of nature, introducing quarks.
'There are a number of different varieties of quarks: there are thought to be at least six "flavours", which we call up, down, strange, charmed, bottom and top. Each flavour comes in three "colours", red, green and blue. ...We now know that neither the atoms nor the protons and neutrons within them are indivisible. So the question is: What are the truly elementary particles, the basic building blocks from which everything is made?'
From this discussion Hawking proceeds to black holes (and the fact that they aren't so black and permanent as popular belief holds them to be), which circles back around to the origin and destiny of the universe (which relates back to the large-scale structure), which ultimately brings us to time. This is where things begin to get interesting.
'When one tried to unify gravity with quantum mechanics, one had to introduce the idea of "imaginary" time. Imaginary time is indistinguishable from directions in space. If one can go north, one can turn around and head south; equally, if one can go forward in imaginary time, one ought to be able to turn around and go backward.'
Hawking explains variations of the thermodynamic, psychological and cosmological laws that regulate the direction of time's arrow, which, despite the theoretical flexibility of time with regard to scientific principles, always apparently goes in one direction.
Finally, Hawking explores the most current topic in theoretical physics: unification theories, which may or may not be a wild goose on the loose. Hawking also explores what such a grand unified theory (also called sometimes the `theory of everything') would mean, and what it wouldn't mean. But Hawking assures us that the quest for understanding is worthwhile even it won't be the final word on everything.
0Commentaire|Ce commentaire vous a-t-il été utile ?OuiNonSignaler un abus
The mark of a true educator, which Stephen Hawking certainly is, is that he would take time (very valuable time, in his case) away from research and contemplation of the great mysteries of the universe to write a piece that would serve to help explain to the greater number of less-scientifically-adept persons the fruits and implications of modern scientific research from the cutting edge of physics. Hawking is ranked in popular and scientific thinking on a par with Einstein, and has motor neuron disability that severely restricts his ability to move, even to type or write, so, when he takes time to write something for general consumption, it is probably going to be worthwhile. And indeed, this is.
'Someone told me that each equation I included in the book would halve sales. I therefore resolved not to have any equations at all. In the end, however, I did put in one equation, Einstein's famous equation. I hope that this will not scare off half of my potential readers.'
Hawking begins by exploring the large scale structure of the universe (time being part of the `fabric' of the universe, in spacetime), the connections of space and time as a relatively new concept in thinking of the universe, and the way the universe `acts' (cosmological dynamics). From there, he explores the universe at a very basic level, as elementary particles and forces of nature, introducing quarks.
'There are a number of different varieties of quarks: there are thought to be at least six "flavours", which we call up, down, strange, charmed, bottom and top. Each flavour comes in three "colours", red, green and blue. ...We now know that neither the atoms nor the protons and neutrons within them are indivisible. So the question is: What are the truly elementary particles, the basic building blocks from which everything is made?'
From this discussion Hawking proceeds to black holes (and the fact that they aren't so black and permanent as popular belief holds them to be), which circles back around to the origin and destiny of the universe (which relates back to the large-scale structure), which ultimately brings us to time. This is where things begin to get interesting.
'When one tried to unify gravity with quantum mechanics, one had to introduce the idea of "imaginary" time. Imaginary time is indistinguishable from directions in space. If one can go north, one can turn around and head south; equally, if one can go forward in imaginary time, one ought to be able to turn around and go backward.'
Hawking explains variations of the thermodynamic, psychological and cosmological laws that regulate the direction of time's arrow, which, despite the theoretical flexibility of time with regard to scientific principles, always apparently goes in one direction.
Finally, Hawking explores the most current topic in theoretical physics: unification theories, which may or may not be a wild goose on the loose. Hawking also explores what such a grand unified theory (also called sometimes the `theory of everything') would mean, and what it wouldn't mean. But Hawking assures us that the quest for understanding is worthwhile even it won't be the final word on everything.
0Commentaire|Ce commentaire vous a-t-il été utile ?OuiNonSignaler un abus
The mark of a true educator, which Stephen Hawking certainly is, is that he would take time (very valuable time, in his case) away from research and contemplation of the great mysteries of the universe to write a piece that would serve to help explain to the greater number of less-scientifically-adept persons the fruits and implications of modern scientific research from the cutting edge of physics. Hawking is ranked in popular and scientific thinking on a par with Einstein, and has motor neuron disability that severely restricts his ability to move, even to type or write, so, when he takes time to write something for general consumption, it is probably going to be worthwhile. And indeed, this is.
'Someone told me that each equation I included in the book would halve sales. I therefore resolved not to have any equations at all. In the end, however, I did put in one equation, Einstein's famous equation. I hope that this will not scare off half of my potential readers.'
Hawking begins by exploring the large scale structure of the universe (time being part of the `fabric' of the universe, in spacetime), the connections of space and time as a relatively new concept in thinking of the universe, and the way the universe `acts' (cosmological dynamics). From there, he explores the universe at a very basic level, as elementary particles and forces of nature, introducing quarks.
'There are a number of different varieties of quarks: there are thought to be at least six "flavours", which we call up, down, strange, charmed, bottom and top. Each flavour comes in three "colours", red, green and blue. ...We now know that neither the atoms nor the protons and neutrons within them are indivisible. So the question is: What are the truly elementary particles, the basic building blocks from which everything is made?'
From this discussion Hawking proceeds to black holes (and the fact that they aren't so black and permanent as popular belief holds them to be), which circles back around to the origin and destiny of the universe (which relates back to the large-scale structure), which ultimately brings us to time. This is where things begin to get interesting.
'When one tried to unify gravity with quantum mechanics, one had to introduce the idea of "imaginary" time. Imaginary time is indistinguishable from directions in space. If one can go north, one can turn around and head south; equally, if one can go forward in imaginary time, one ought to be able to turn around and go backward.'
Hawking explains variations of the thermodynamic, psychological and cosmological laws that regulate the direction of time's arrow, which, despite the theoretical flexibility of time with regard to scientific principles, always apparently goes in one direction.
Finally, Hawking explores the most current topic in theoretical physics: unification theories, which may or may not be a wild goose on the loose. Hawking also explores what such a grand unified theory (also called sometimes the `theory of everything') would mean, and what it wouldn't mean. But Hawking assures us that the quest for understanding is worthwhile even it won't be the final word on everything.
0Commentaire|Ce commentaire vous a-t-il été utile ?OuiNonSignaler un abus
The mark of a true educator, which Stephen Hawking certainly is, is that he would take time (very valuable time, in his case) away from research and contemplation of the great mysteries of the universe to write a piece that would serve to help explain to the greater number of less-scientifically-adept persons the fruits and implications of modern scientific research from the cutting edge of physics. Hawking is ranked in popular and scientific thinking on a par with Einstein, and has motor neuron disability that severely restricts his ability to move, even to type or write, so, when he takes time to write something for general consumption, it is probably going to be worthwhile. And indeed, this is.
'Someone told me that each equation I included in the book would halve sales. I therefore resolved not to have any equations at all. In the end, however, I did put in one equation, Einstein's famous equation. I hope that this will not scare off half of my potential readers.'
Hawking begins by exploring the large scale structure of the universe (time being part of the `fabric' of the universe, in spacetime), the connections of space and time as a relatively new concept in thinking of the universe, and the way the universe `acts' (cosmological dynamics). From there, he explores the universe at a very basic level, as elementary particles and forces of nature, introducing quarks.
'There are a number of different varieties of quarks: there are thought to be at least six "flavours", which we call up, down, strange, charmed, bottom and top. Each flavour comes in three "colours", red, green and blue. ...We now know that neither the atoms nor the protons and neutrons within them are indivisible. So the question is: What are the truly elementary particles, the basic building blocks from which everything is made?'
From this discussion Hawking proceeds to black holes (and the fact that they aren't so black and permanent as popular belief holds them to be), which circles back around to the origin and destiny of the universe (which relates back to the large-scale structure), which ultimately brings us to time. This is where things begin to get interesting.
'When one tried to unify gravity with quantum mechanics, one had to introduce the idea of "imaginary" time. Imaginary time is indistinguishable from directions in space. If one can go north, one can turn around and head south; equally, if one can go forward in imaginary time, one ought to be able to turn around and go backward.'
Hawking explains variations of the thermodynamic, psychological and cosmological laws that regulate the direction of time's arrow, which, despite the theoretical flexibility of time with regard to scientific principles, always apparently goes in one direction.
Finally, Hawking explores the most current topic in theoretical physics: unification theories, which may or may not be a wild goose on the loose. Hawking also explores what such a grand unified theory (also called sometimes the `theory of everything') would mean, and what it wouldn't mean. But Hawking assures us that the quest for understanding is worthwhile even it won't be the final word on everything.
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le 23 décembre 2012
Bien reçu, très rapide ! Et livre extra ;)
Les prix (livre et frais de port) sont très raisonnables. Je recommande cet acheteur et ce livre !

Joyeuses fêtes de fin d'année
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le 1 mars 2014
No wonder this book was such a big hit when it was first released - the story it tells of Time and Space is facinating and it is told without recourse to heavy technicalities. It is an amazing piece of work and is just as relevant today as it was when first published. If you want to read about what space and the cosmos mean then this is the first stop, even for me it was enjoyable and still interesting to read the thoughts of a true genius.
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