The Singular Universe and the Reality of Time: A Proposal in Natural Philosophy (英語) ハードカバー – 2014/12/8
Kindle 端末は必要ありません。無料 Kindle アプリのいずれかをダウンロードすると、スマートフォン、タブレットPCで Kindle 本をお読みいただけます。
Cosmology is in crisis. The more we discover, the more puzzling the universe appears to be. How and why are the laws of nature what they are? A philosopher and a physicist, world-renowned for their radical ideas in their fields, argue for a revolution. To keep cosmology scientific, we must replace the old view in which the universe is governed by immutable laws by a new one in which laws evolve. Then we can hope to explain them. The revolution that Roberto Mangabeira Unger and Lee Smolin propose relies on three central ideas. There is only one universe at a time. Time is real: everything in the structure and regularities of nature changes sooner or later. Mathematics, which has trouble with time, is not the oracle of nature and the prophet of science; it is simply a tool with great power and immense limitations. The argument is readily accessible to non-scientists as well as to the physicists and cosmologists whom it challenges.
'It might be one of the most important books of our time … Right or wrong, this book is an event.' Bryan Appleyard, The Sunday Times
'A hefty explication setting out clear agendas for research into quantum foundations, explanations for the 'arrow of time' and other parts of this puzzle.' Nature
'Any serious intellectual rebellion is worth watching. This one is ambitious: it seeks to root out one of the oldest impulses in the western imagination.' The Spectator
'Is time, after all, real? Two mavericks take an axe to the established theories of cosmology.' The Guardian
'… an admirable restatement of cosmological ambition.' The Times Higher Education Supplement
'Anyone that wants to thoroughly deliberate over the question of cosmology should read this book.' Peter Eisenhardt, translated from Physik Journal
Amazon.com で最も参考になったカスタマーレビュー (beta) （「Early Reviewer Program」のレビューが含まれている場合があります）
The traditional Newtonian paradigm of scientific methodology, with its static background space and time, immutable laws of physics directing casual events, and requirement of unexplained initial conditions and constants of nature, along with present interpretations of general relativity that suspect an infinite singularity as the beginning of the universe, are too constricting to break through the cosmological impasse. It’s not the first time in the physical sciences when such a paradigm change was called for. As Richard Feynman once said,….
“Each time we get into this log-jam of too much trouble, too many problems, it is because the methods that we are using are just like the ones we have used before. The next scheme, the new discovery, is going to be made in a completely different way.” – The Character Of Physical Law
To this end, a very interesting and innovative approach is presented here by Unger and Smolin….
The initial singularity interpretation of general relativity exposes the breakdown of that theory. If such an impasse is to be surmounted, the influence of the purely mathematical and non-physical notion of the infinite, must give way to, albeit very high, but finite density and temperature in the past history of the universe.
Also, the laws of nature themselves should be liable to change,... not in the sense of a meta-law guiding that change, but rather in the sense that causality is taken as more fundamental than ‘laws of nature’. Under the traditional Newtonian methodology, it is rather the other way around,… that causal connections are driven by immutable laws of nature. In this innovative scenario, causal connections with no law like regularities become a theoretical possibility.
With the further presumption, necessary given the above, of the inclusive 'reality of time', it is then possible to consider that the laws of nature are mutable and contingent upon casual connections and that the universe can be studied as having a history both with respect to laws of nature derived from causal connections, and the traditionally unexplained initial conditions, constants, and symmetries of nature. Incidentally, this notion of an inclusive 'cosmological time', is not incompatible with local time dilation nor failure of simultaneity implied by the well tested general relativity theory.
Despite having contentions with their form of argument (see below), especially with respect to the concept of Time, I did enjoy this book, as many important and innovative ideas are presented here.
That causality is more fundamental than ‘laws of nature’, and that ‘laws of nature’ are therefore emergent in a sense, could have been derived from epistemological considerations. As a result, their argument did not go far enough in my opinion. As David Hume and Immanuel Kant have argued, there is no analytic link between events to begin with. What we call ‘causality’, is merely a constant conjunction of observations that are subject to an artificial synthesis given the a-priori conditions for the understanding. This was not to deny the causal principal, as Hume did not, but rather was to deny the possibility of knowing objectively the underlying operating powers of reality existent between observable events that are purported to be linked via the concept of causality.
Indeed as Unger/Smolin correctly pointed out, there can be no one-to-one correspondence between mathematical structures and observable events. They are correct to question physical theories that rely on such mathematical idealism. However, again their argument could have referenced epistemology; It is rational to argue that rather than deriving concepts, like time and causality, from experience as Smolin implies,… it is rather the other way around, that experience itself is not possible except by virtue of those concepts,… that they are the condition for experience to be possible to begin with, given the nature of mind. As with time and space, the core elements of mathematics are a-priori judgments of intuition, a la Kant, hard-wired in the mind via evolution in order to synthesize experience. These conceptual forms of thought, give only the illusion that they are intrinsic features of independent reality, or that there is an ‘unreasonable effectiveness of mathematics to the natural sciences’, because rationalization of empirical experience must necessarily be in terms of these conceptual forms, given the nature of mind. On this basis, the 'unreasonable effectiveness of mathematics' is not mysterious at all, for the same reason that the non-intuitive nature of quantum mechanics is not mysterious; .... it is an artifact of an artificial synthesis via necessary a-priori concepts, given the evolved conditions for mind to be able to synthesize experience and to observe at the macroscopic level.
"In biology, the possible laws that govern biological phenomenon emerge with those phenomenon" – Smolin/Unger
Likewise, the very possibility of a synthesis of experience, emerge via evolutionary biology, with an a-priori conceptual structure intrinsic to the mind and its means of processing experience. Kant's categories, or 'forms of thought' which include time and space as intuitions as well as the elements of mathematics, are a-priori conditions for the ordering of experience for the understanding. This inherent conceptual framework of the mind is exposed as an artificial synthesis of reality on account of non-intuitive physical theories or interpretations thereof,... i.e. quantum mechanics, and aspects of general relativity.
Time as an intuitive concept should not actually used in physics theories. For example, Einstein was careful to use an operational or instrumentalist Definition of time (and space), by which time is Defined as simply another physical system unto itself, i.e. a light-clock. This designated physical system is found to be effected in the presence of mass-energy. Through a kind of epistemological knot, it is then stated that time slows down in the presence of mass-energy. An inclusive ‘cosmological time’ would need to be operationally defined as well, as some physical system or observational data set, that is observer independent.
This is two books by two authors. Please read the second book first (Smolin). The second book (Smolin) has a very low thought per word ratio. By this I mean that he generates new and important ideas with few words. Smolin gets right down to the issues. I know how much effort and rework that takes as opposed to the wandering, referential stream-of-consciousness modes (Unger).
I almost quit reading this book at page 37 as I floated through Unger's book. I jumped to Smolin, read that, and can now wander through Unger when time allows. I would suggest that the publisher switch the order of the two books in the next versions, or even make it two books.
As to the content from Smolin's book, I think it begins to address the real detail overwhelming us in the universe as it really is. The simple models are useful, but avoid the scale, uniqueness and interactive unity of the real thing. Good luck putting that in a bottle!
Neither book is "popular science", but rather both are serious attempts at a novel "natural philosophy" that contributes (or should contribute) to advancing the subject of cosmology by illuminating little considered implications and interpretations of the physical (standard model) and cosmological data we already have.
Unger's approach is more purely philosophical. He begins straightforwardly enough with the common (in science) metaphysical assumption that only the material universe is real. Although he abjures a strong metaphysics and offers instead what he calls a "proto ontology" that does not attempt to fix the kinds of things there are in the universe for all time, he is nevertheless stuck with this basic materialism and that forces him onto one of two horns of a dilema. The mystery is the extreme unlikeliness of "the settings" that make the universe hospitable to life. Most physicists being philosophically trapped in the "block universe" model of relativistic time (which in effect denies the fundamentality of time by casting time in terms of spatial geometry) have gone over to the multiverse as an (untestable) explanation (along with the "anthropic principle) for the unlikely values of the settings in our universe. From Unger's viewpoint, the opposite tack, assuming time to be both real and fundamental, and that there is a global "preferred time" (perfectly compatible with relativity given appropriate alterations in what Unger calls its "metaphysical gloss") which all means that there is nothing in the physical universe that is immune from the effects of time including the laws and settings which change (albeit in this universe phase very slowly) and that instead of multiple universes, the unlikeliness of our settings is explained by our one universe having an indefinite (not eternal) past that has gone through phases having various settings and has just happened, in this phase, to end up with the settings it has. Unger believes that this option, the "indefinite past" and a single universe at a time is better than the multiverse hypothesis because it provides for a causal (although the laws governing causal interactions will be different from phase to phase) continuance between phases. Time and causation entail one another, they are both fundamental in that what ever the laws and settings operative at a given moment happen to be, there is still some sort of causal interaction in time. As difficult as it might be to detect records of past universe phases (that is prior to our own big bang) such detection remains possible and therefore within the scope of science, while non-communicating multiverses that preclude any interaction do not.
Unger covers his ground very well. His approach is to revisit the same questions and issues over and over again like a skeleton on which he lays a little more flesh with each pass. In the end he leaves out two things. He offers no specific explanation for our particular settings this time around, and he fails to address how it is that the laws and settings we measure in our universe phase happen to hold over a range of conditions from the cold of interstellar space to the interior of stars. He admits that in our present "cooled down" universe the laws and settings appear very stable. His failure to offer any explanation for their stability does not detract from the argument that time is real and there is only one universe at a time. He explicitly leaves the rest to Lee Smolin.
Smolin is a physicist writing here as a natural philosopher and he is very good at it. His argument here is a reprise of his book "Time Reborn". He's had a few years to chew over these ideas, and I think his more concise treatment here is clearer than it was in that book. Smolin does offer two possibilities for explaining what Unger leaves out. The first is his "principle of precedence" which goes only part of the way, explaining how it is that the settings might get set, but not why they are what they are. The second, his notion of "cosmological natural selection" does actually explain both the settings and to some extent their stability across the wide range of conditions in our present universe. But these explanations rely on two rather speculative ideas.
First, new universes arise from the interior of black holes. The point of the settings and their stability is that these two properties are necessary to produce lots of black holes from massive stars. Such black holes in effect set the parameters of the universes they generate. Our own universe is in fact such a baby universe generated by a black hole in another universe. Second, the range of possible (or likely) settings of the baby universe would be different than those of the parent universe but only and always in a small range. This is what sets up the "natural selection".. Universes whose properties happen to produce a lot of those kinds of black holes will end up dominating a history of branching universes such that the great majority of them have settings similar to ours just so that they can produce a lot of black holes.
Of course the very idea that universes are born in black holes (or that ours emerged from a black hole) is at present utterly beyond observational science, so this is sheer speculation whose only relation to physics (as distinct say from asserting that "God did it") is that there is a potential causal chain (no matter what transformation the settings might undergo in between) connecting parent (black hole) to child (new universe). Smolin fails to say why it is that the variation in settings through black holes from massive stars (he explicitly rejects primordial black holes as selectable parents for this reason) should vary by only a little.This property is what makes them selectable. If the settings vary by very much, the outcomes (as far as black hole creation are concerned, not to mention life) will be random and not converge to an optimal type. There is no mention here that the coincidence of these same settings being conducive to life AND black holes is itself something of a mystery. Dr. Smolin spends a small chapter addressing the nature of qualia in consciousness, but he is interested in suggesting an example of precedent-agnostic causation (brain correlates of qualia) and not the coincidence of settings conducive to both black holes and life.
Both men address "the unreasonable effectiveness of mathematics", and claim, reasonably enough given their history-first foundation, that present mathematics happens to be fit-able to present physics but that the discipline has no magic insight into the nature of every particular event in the history of the universe (Smolin) or into some Platonic structure that is metaphysically prior to actual history taken in aggregate (Unger). This is one of the more fascinating parts of both arguments because both men get to the same place about math in very different ways.
It is unfair to criticize either author for not solving every problem. For both this book is to be the foundation of a natural philosophy, not its completed edifice. Both author's arguments rest on a foundation of time, causation, and therefore history as being fundamental. The universe is what it is and if we discover structure in its behavior, that structure, mathematically describable regularities, it doesn't mean those very regularities weren't different in the past and won't change in the future. There is every reason to believe they are both onto something here. Smolin's illustration of how we slip from an observation of causal stability in the present universe to a mistaken notion of absolutely deterministic precedents is illuminating to say the least. All of this above does not do justice to the over-all philosophical integrity of this work. Drs. Unger and Smolin happen to discover in one another kindred spirits as far as this business of the reality and fundamentality of time is concerned. I hope there will be more collaborations between them in the future.