The Hidden Reality: Parallel Universes and the Deep Laws of the Cosmos

This is an impressive survey of 9 multiverse models by Greene featured in lucid, engaging and effortless prose. This should be a go to book for the public as well as physics students for a conceptual understanding of the multiverse models available. He began with the "Quilted multiverse" model. This model sets up the most basic bare bone structure of the rationale of multiverse theory. Consider our own visible universe's cosmic horizon of a 14 billion year old universe. The cosmic horizon visible to us is only 41 billion light years (distance based on the light coming from objects receding from us). Our cosmic horizon or patch is all there is ever visible to us. The entire universe in the infinite space can contains infinite number of patches each with it's own cosmic horizon, constituting a quilted universe. Each patch is out of reach of the other patches. This is a basic multiverse model showing each multiverse in its own cosmic horizon patch. The "inflationary model" from Alan Guth and Andrei Linde offers further mechanism to account for how the vast expanse of the multiverse can be built out. The idea is an inflation that is triggered by quantum jitter in high energy inflation field level causing it to expand and bubble out into different multiverses. This inflationary mechanism is also commonly used in other multiverse models. Greene, as a String theorist, offers the String Theory model of multiverse by considering our 3 dimensional expanse universe on a 3-brane sheet. Another multiverse would be on another 3-brane sheet, and there can be as many 3-brane sheets on which each multiverse exists. This multiverse model is the "Brane Multiverse" model. Another String Theory model is the "Landscape" model offered by Suskind. In this model, an inflationary mechanism for bubbling into multiverse is augmented with a further feature of quantum tunneling. A multiverse suffused with higher energy level or cosmological constant can expand via repulsion and inflate, but tunnels or drops down to a lower energy level for bubbling into another multiverse. The multitude of landscape with different cosmological constants represented by unique Calabi Yau manifolds can continue and repeat this tunneling process for proliferating further multiverses. Greene also offers a thorough discussion of the Everttian "multiple-world quantum" model. In this model, the Everttian interpretation of quantum mechanics by branching the possible outcomes of quantum state into different worlds is treated as another multiverse model. Instead of collapsing probability amplitudes as in Copenhagen interpretation, Evertt suggested to let probability outcomes to branch out into different worlds such that each outcome constitute its own world. Greene highlighted that Everttian rationale is that multi-world interpretation actually stays faithful to Schrodinger equation and let the equation results speak for itself instead of ad hoc adding probability amplitudes together which are not reflected in the equation. Greene also discussed if such a multi-world interpretation takes quantum probability seriously, which he thinks each multi-world is still a probabilistic outcome. Another model Greene discussed in this work is the conceptually challenging "Holographic multiverse" model. In this model, our universe is a mere holographic phenomena taking place on a distant bounding surface, a physically equivalent parallel universe. In the holographic principle, open strings movement on 3-branes is described by quantum field particle theory in four dimensional space-time. The physics described is the same as the closed loop strings on 10 dimensional black branes as long as the strings at low energy are closed to the event horizon surface. Hence the holographic model reveals universes as holograms of equivalent parallel universes. Three other models discussed are the Cyclic multiverse model and the mathematical models of "Simulated Multiverse" and "Ultimate Multiverse" models which consider mathematical multiverses to be as real as physical multiverses. There is also a chapter devoted to methodological issues such as experimental accessibility, predictions, and the limits of mathematical applicability to physics.

Brian Greene belongs to the rare breed of scientists who like to explain deep scientific concepts in simple words so that common people can understand it and connect with the concepts. Let it be general theory of relativity, quantum mechanics, string theory or multiverse theory, Brian Greene explains them so well that not only he gets readers to understand the gist of these theories but also gets them to ponder upon implications and extension of it. This book is about human endeavor to understand reality. Throughout the history of humanity, we have pondered about natural phenomena and come up with explanations behind them. Newton came up with laws of motion and mathematical equation for working of gravity. Einstein transformed our understanding of time and space with general theory of relativity, Heisenberg and others transformed our understanding of world of small particles with quantum mechanics – we are continuing with the scientific march to push boundaries of human knowledge. Our increasing understanding of universe has brought us at corner of whole new realm – the concept of multiple universes. Before reading this book, I considered concept of multiple universes to be one of interesting but otherwise purely theoretical hypothesis. But this book presents multiple universe system as logical and mathematical extension of our already existing and proven scientific theories. In fact, this book defines not one but about 9 different types of multiple universes that stems from existing theories such as quantum mechanics and string theory. These theories represents pinnacle of human knowledge till date, they indicate how far we have reached till date in understanding reality. Multiverse theory is only theory that looks promising enough to answer 'Why there is something rather than nothing?' and Brian Greene has done a great job explaining it.

(As posted at amazon.com) I learnt (& reconfirmed) a lot about current theories of universe or multiverse from this book and hence, put 5 stars. There are two points I would like to mention after reading this book: (1) Is our existence on the Earth really meaningless, i.e., accidental? (2) Why do we perceive only three dimensions of space, not 4 or 9 or 10? Point (1): It appears that advancements made by modern science in the 20th and 21st centuries have made our existence in this particular corner of the universe increasingly more enigmatic'as if our existence was preordained in a Grand Design; hence comes the first question. Professor Greene explains an answer to the question based on modern science. One idea to make the enigma mundane, statistically, is the idea of multiverse of several theoretical types (albeit existing proponents and detractors of the idea), which may consist of a huge number of universes, and our life-friendly universe is not anything special but merely one of them. Point (2): As we listen to Prof. Greene in the amazon.com video, he explains the possible reasons based on the idea of curled-up dimensions or the extra-dimension connecting the 'braneworlds,' and to experimentally verify the idea, some particle physics experiments are now going on at CERN using the LHC. Physicists are carefully accounting input vs. output energies in the experiments. And if other extra-dimensional models proposed by physicists describe the universe, some small fraction of energy (in the form of gravitons of loop-shaped string) will disappear into the unobservable fifth-dimension (i.e., unobservable to people confined in the four-dimensional spacetime-brane) and we will ultimately conclude the existence of those extra-dimensions. Now, because of my being a non-materialist, may I have an opportunity to refer to some other non-materialistic ideas explaining these two issues? Regarding Point (1): i.e., meaningfulness of our existence on the Earth Just as materialistic science assumes that in the beginning there exist elementary particles or strings materialized from some pure energy, the non-materialistic idea assumes that in the beginning there exists 'unit of consciousness (CU in short)' in some non-physical dimensions; and everything in the physical dimension is the results of the CUs combining each other to form meaningful physical objects, including life on Earth, based on some '(eleven) universal laws,' which transcend our physical laws. So in this idea, existence of life on the Earth is teleological from the start. According to this idea, there will be no meaningless universes; no need to explain 'how come the consciousness out of elementary particles or strings?' Of course need to explain 'how come the CUs?' This non-materialistic idea, i.e., 'psychical knowledge,' so to speak, comes from the book by an American writer, poet, and trance channeler, Jane Roberts (1929-1984): The 'Unknown' Reality, Vols. 1 & 2 (originally published in 1977 & 1979 from Prentice-Hall, now from Amber-Allen). This book is counter to Prof. Greene's The Hidden Reality. Einstein says 'energy and mass are different manifestations of the same thing (i.e., E = Mc^2).' The psychical knowledge says 'consciousness and matter and energy are one, but consciousness initiates the transformation energy into matter.' This is one of the important points of the traditional psychical research, in which an apparently living human form is materialized by a legitimate physical medium. Regarding Point (2): Why do we perceive only three dimensions of space, not 4 or 9 or 10? The psychical knowledge explains to the effect as follows: What we call dimensions represent states in which reality is perceived. We perceive reality in three dimensions, and we have a glimpse of reality in a fourth dimension [e.g., the fourth-dimensional cube known as tesseract]. There are many dimensions however in all directions. [These heavenly bodies represent moment points in other systems. As they are projected into our system however, they are only perceived in terms of matter with our physical senses. The psychical knowledge tells further.] These dimensions merely represent various capacities of consciousness. All these dimensions exist at once, and even within our system, but our consciousness cannot perceive them. (Based on Roberts, J. [1999]. The Early Sessions: Book 6 of the Seth Material: pp. 152−154, Session 258 on May 11, 1966, Manhasset, NY: New Awareness Network) Hence, the reason why we cannot perceive more than three dimensions is because of our consciousness being at such a lower developmental stage! Maybe Emanuel Swedenborg (1688-1772) was at a lot advanced stage of his consciousness, as expressed in his book 'The Earths in the Universe and their Inhabitants (1875).' Because, very probably, there will be criticisms against my posting, saying my writing nonsense, waste of website space, I would like to mention one more point in advance to cope with such possible criticisms. I believe in the weight of soul: the 21 g of missing weight (i.e., unaccountable energy balance) detected by Dr. Duncan MacDougall for his first subject in his experiment published in 1907. Although physics Prof. Robert L. Park states in his book (Superstition: Belief in the Age of Science (2008)) to the effect that the missing weights are the result of MacDougall's wishful thinking and superstitious nonsense, no scientist has ever scientifically either refuted or confirmed the missing weights. Rather, recently a paper was published in the Journal of Scientific Exploration, 2010 Spring Issue (Vol. 24, No.1, pp. 5-39: Rebuttal to Claimed Refutations of Duncan MacDougall's Experiment on Human Weight Change at the Moment of Death. [This Vol.24/No.1 is on sale at amazon.com.]), which supports MacDougall's experiment being scientifically sound on a basis of theoretical simulations of the weighing experiment. The missing weight, if confirmed authentic, is quite relevant to the two points discussed above, because (1) it suggests our life on the Earth being not meaningless, and (2) it suggests existence of non-physical extra-dimensions for afterlife.

Fantastico como Greene consigue hacernos entender a todos los conceptos más complejos

Brian Greene starts off this book introducing the concept of multiple universes. According to Greene (I'm not a physicist) many, if not most, physics theories lead to some kind of multiple universe solution. They don't all agree on exactly what kind of multiple, parallel, alternate, string, infinite universes exist, but they do suggest that such universes do in fact exist. This forces us to change our concept of universe from everything we could possibly measure to everything that could possibly exist. The book presents eight chapters that focus on explaining different potential multiverses along with two chapters that focus on explaining how we can use math and science to learn about these multiverses and what some limitations might be for our learning about them. Including the introduction, it makes for around 320 pages plus references, but it's actually relatively light reading. Relatively being the key. This isn't "See Spot Run". This is a discussion of the nature of, well, everything. I must admit that I was initially a little disappointed that there isn't an easy, simple solution to the nature of everything. Then I realized that would probably be a little boring and almost certainly wouldn't be true. Fortunately, Greene does a good job making hard topics easy to understand. This is partly due to the fact that complex phenomena must often be reduced to something simpler for even physicists to wrap their heads around them, and partly due to the fact that Greene is very good at making tough concepts easy to get. Most chapters start of with a review of the prerequisite physics for a particular multiverse view. This introduction can be skipped by advanced readers, but more casual science readers (like myself) will find it a very helpful primer or reminder (e.g., of S. Hawking's books). The next part of the chapter delves into the particular theory in question and what kind of universe(s) that theory predicts. The last part of each chapter is more theoretical, asking more complex questions, suggesting future directions, and/or offering extensions of the theory in question. Overall, it makes for good reading as the reader is handily moved from easier to more complicated material. I tend towards biological science reading, but I'd heard such good things about Greene's writing that I thought I'd give this book a shot. I'm glad I did. The only downside is that I now find myself daydreaming about possible universes when I should be thinking about other things. But that's hardly a serious fault for the book. Just the opposite in fact. The idea that there are likely multiple universes, some potentially just like ours, with an exact copy of me typing this exact review or an exact copy of you reading it, is just really, really cool. And that kind of cool is just what good science reading should be all about!