I enjoy reading about parallel and multiverses that come about from some areas in current theoretical research in fundamental physics. I selected this book of the many on the topic of parallel universes since it was written by Brian Greene who is a string theorist and is working on a variety of these topics. He is a person truly gifted with explaining complex topics in physics in ways that make them easier to understand.
Greene in this book lays out and explains nine different versions of parallel universes. The deep laws are those of quantum mechanics and general relativity. The explanations of all subjects are as expected clear and supported with an excellent notes section in the back.
If you want to learn about parallel universes and the ideas that they come from this is an excellent book to read. That's why the book gets a four star rating. All nine of the parallel universes are based on speculative physics. Some much more speculative than others. That these theories are speculative he admits throughout the book for which he deserves credit.
STRIKING BACK PARALLEL WORLDS BOOK 3 KINDLE EDITION - In this site isn`t the same as a solution manual you buy in a book store or download off the. THE PARALLEL UNIVERSES of your alter egos constitute the. Level I But recent observations of the three-dimensional galaxy distri- .. AVE BACK . science-fiction novel Permutation City and developed by .. But one striking and.
However, in reading this book I got the feeling that this book was the long version of a grant proposal submitted to be funded. This comes about in the numerous places in which he says much has been done but give us more time to work on these ideas. The theory so far is not even falsifiable. The same criticism is also true for the multiverses that come from inflationary. However, there are a large number of sharp physicists working in these areas so it is unclear what the future holds.
Parallel universe's from Hugh Everett's thesis work on the interpretation of quantum mechanics, now known as the many worlds interpretation is another area of current research in physics and philosophy. This work is based on the measurement problem in quantum mechanics. Greene suggests an experiment in the notes to test this theory, but it is unclear if this has been clearly thought out and if this experiment is even possible.
The discussion on computer simulated universes is interesting.
It describes a universe similar to that in the movie "The Thirteenth Floor". While not a parallel universe in ways that physics suggests a simulated universe would make the ultimate computer game. A virtual reality that could absorb the programmers life into the simulation.
Almost the ultimate drug. Live life to its fullest would have an additional impetus if you live in a simulated universe so that the creator of the simulation would not get bored with you and stop the simulation. However, since you can't prove that you are living in a simulated universe, do you need to live a life to satisfy the simulator? The final chapter entitled "The Limits of Inquiry Multiverses and the Future" is well written and makes an interesting conclusion to the book. Dr Greene has written a book that deals with the multiverse and in particular, and the reason I bought the book, is he deals with the possibilities of us being in a SImulation.
Look out, Twilight Zone! A case in point is the movie Thirteenth Floor, as well as Matrix, wherein the main characters are not dealing with 3D physical reality -- they have more of a SImulation, and this idea intrigues Dr Greene. The application of the idea also intrigued the author of Virtual Earth Graduate and he Hegland goes into quite some detail in 2 chapters relating how Earth really could be a SImulation, albeit a very sophisticated one. And there are many physicists who are now saying the same thing about Earth and offer credible reasons for thinking thus While the idea sounds silly on the surface, one of Dr Greene's key points there are several is that physical constants of the Universe should not be changing -- the speed of light, the decay rate of radioactive material, C dating, etc To really get a sense of this issue, one needs to see the movie Thirteenth Floor.
And if we are simulated, is the next level 'up' which drives our SImulation itself simulated? And then do we live in a SImulated Multiverse? And what happens when one of the simulations crashes? Dr Greene's book is fascinating in this regard.
Dr Greene's other main point was that over time, with mathematics that is not carried to decimal points with infinite precision, there are going to be recursions of the same formulas and their outputs which will suffer rounding and approximations to the point where internal consistency is lost, sections of the SImulation would become incoherent, and the Simulation will crash -- is that what happened to the Maya back in AD when they just all disappeared? See Virtual Earth Graduate for a better, longer review of this issue.
Other physicists suggest that the Earth may be in a quantum computer running "qubits" and they theorize that just the Earth not the universe would be scalable to run within the memory confines of the largest computer that we can build nowadays If this idea fascinates you, check out those books mentioned. Parts of the concept are not froo-froo and this gives cause to reflect In short, if quantum physics annoys you, or you just can't feature some of the strange postulates, then try Dr Paul LaViolette's Genesis of the Cosmos book -- he says that Subquantum Kinetics using the ether has better answers than does quantum physics with its Dark Matter Afficher ou modifier votre historique de navigation.
Calculations showed that most galaxies and therefore most observers are in regions where the dark energy is about the same as the density of matter at the epoch of galaxy formation. The prediction is therefore that a similar value should be observed in our part of the universe. For the most part, physicists did not take these ideas seriously, but much to their surprise, dark energy of roughly the expected magnitude was detected in astronomical observations in the late s. This could be our first evidence that there is indeed a huge multiverse out there. It has changed many minds. The multiverse theory is still in its infancy, and some conceptual problems remain to be resolved.
Inspired by an interesting critique of multiverses in the August issue of Scientific American, penned by relativity pioneer George F. Ellis, let my give you my two cents' worth. Multiverse ideas have traditionally received short shrift from the establishment: Giordano Bruno with his infinite-space multiverse got burned at the stake in and Hugh Everett with his quantum multiverse got burned on the physics job market in I've even felt some of the heat first-hand, with senior colleagues suggesting that my multiverse-related publications were nuts and would ruin my career.
There's been a sea-change in recent years, however. Parallel universes are now all the rage, cropping up in books, movies and even jokes: This airing of ideas certainly hasn't led to a consensus among scientists, but it's made the multiverse debate much more nuanced and, in my opinion, more interesting, with scientists moving beyond shouting sound bites past each other and genuinely trying to understand opposing points of view. George Ellis's new article is a great example of this, and I highly recommend reading it if you haven't already.
By our universe, I mean the spherical region of space from which light has had time to reach us during the When talking about parallel universes, I find it useful to distinguish between four different levels: Level I other such regions far away in space where the apparent laws of physics are the same, but where history played out differently because things started out differently , Level II regions of space where even the apparent laws of physics are different , Level III parallel worlds elsewhere in the so-called Hilbert space where quantum reality plays out , and Level IV totally disconnected realities governed by different mathematical equations.
The discussion on computer simulated universes is interesting. I enjoy reading about parallel and multiverses that come about from some areas in current theoretical research in fundamental physics. A Brief History Of Time: George lists a number of observations purportedly supporting multiverse theories that are dubious at best, like evidence that certain constants of nature aren't really constant, evidence in the cosmic microwave background radiation of collisions with other universes or strangely connected space, etc. Some of the fine-tuning appears extreme enough to be quite embarrassing—for example, we need to tune the dark energy to about decimal places to make habitable galaxies. Back Bay Books,
In his critique, George classifies many of the arguments in favor of these multiverse levels and argues that they all have problems. Here's my summary of his main anti-multiverse arguments:. George didn't actually mention 2 in the article, but I'm adding it here because I think he would have if the editor had allowed him more than six pages. What's my take on this critique? Interestingly, I agree with all of these seven statements—and nonetheless, I'll still happily bet my life savings on the existence of a multiverse!
Let's start with the first four. Inflation naturally produces the Level I multiverse, and if you add in string theory with a landscape of possible solutions, you get Level II, too. Quantum mechanics in its mathematically simplest "unitary" form gives you Level III. So if these theories are ruled out, then key evidence for these multiverses collapses. To me, the key point is that if theories are scientific, then it's legitimate science to work out and discuss all their consequences even if they involve unobservable entities.
For a theory to be falsifiable, we need not be able to observe and test all its predictions, merely at least one of them. My answer to 4 is therefore that what's scientifically testable are our mathematical theories, not necessarily their implications, and that this is quite OK. For example, because Einstein's theory of general relativity has successfully predicted many things that we can observe, we also take seriously its predictions for things we cannot observe, e. Likewise, if we're impressed by the successful predictions of inflation or quantum mechanics so far, then we need to take seriously also their other predictions, including the Level I and Level III multiverse.
George even mentions the possibility that eternal inflation may one day be ruled out—to me, this is simply an argument that eternal inflation is a scientific theory. String theory certainly hasn't come as far as inflation and quantum mechanics in terms of establishing itself as a testable scientific theory. However, I suspect that we'll be stuck with a Level II multiverse even if string theory turns out to be a red herring. It's quite common for mathematical equations to have multiple solutions, and as long as the fundamental equations describing our reality do, then eternal inflation generically creates huge regions of space that physically realize each of these solutions.
For example, the equations governing water molecules, which have nothing to do with string theory, permit the three solutions corresponding to steam, liquid water and ice, and if space itself can similarly exist in different phases, inflation will tend to realize them all. George lists a number of observations purportedly supporting multiverse theories that are dubious at best, like evidence that certain constants of nature aren't really constant, evidence in the cosmic microwave background radiation of collisions with other universes or strangely connected space, etc.
I totally share his skepticism to these claims. In all these cases, however, the controversies have been about the analysis of the data, much like in the cold fusion debacle. To me, the very fact that scientists are making these measurements and arguing about data details is further evidence that this is within the pale of science: Our universe appears surprisingly fine-tuned for life in the sense that if you tweaked many of our constants of nature by just a tiny amount, life as we know it would be impossible. If there's a Level II multiverse where these "constants" take all possible values, it's not surprising that we find ourselves in one of the rare universes that are inhabitable, just like it's not surprising that we find ourselves living on Earth rather than Mercury or Neptune.
George objects to the fact that you need to assume a multiverse theory to draw this conclusion, but that's how we test any scientific theory: Some of the fine-tuning appears extreme enough to be quite embarrassing—for example, we need to tune the dark energy to about decimal places to make habitable galaxies. To me, an unexplained coincidence can be a tell-tale sign of a gap in our scientific understanding.
Dismissing it by saying "We just got lucky—now stop looking for an explanation! George argues that if we take seriously that anything that could happen does happen, we're led down a slippery slope toward even larger multiverses, like the Level IV one.
Since this is my favorite multiverse level, and I'm one of the very few proponents of it, this is a slope that I'm happy to slide down! George also mentions that multiverses may fall foul of Occam's razor by introducing unnecessary complications. As a theoretical physicist, I judge the elegance and simplicity of a theory not by its ontology, but by the elegance and simplicity of its mathematical equations—and it's quite striking to me that the mathematically simplest theories tend to give us multiverses.
It's proven remarkably hard to write down a theory which produces exactly the universe we see and nothing more. Finally, there's an anti-multiverse argument which I commend George for avoiding, but which is in my opinion the most persuasive one of all for most people: Having looked at anti-multiverse arguments, let's now analyze the pro-multiverse case a bit more closely. I'm going to argue that all the controversial issues melt away if we accept the External Reality Hypothesis: Suppose that this hypothesis is correct. Then most multiverse critique rests on some combination of the following three dubious assumptions:.
The omnivision assumption effectively redefines the word "exists'' to be synonymous with what is observable to us humans, akin to an ostrich with its head in the sand. Those who insist on the pedagogical reality assumption will typically have rejected comfortingly familiar childhood notions like Santa Claus, local realism, the Tooth Fairy, and creationism—but have they really worked hard enough to free themselves from comfortingly familiar notions that are more deeply rooted?
In my personal opinion, our job as scientists is to try to figure out how the world works, not to tell it how to work based on our philosophical preconceptions.
If the omnivision assumption is false, then there are unobservable things that exist and we live in a multiverse. If the pedagogical reality assumption is false, then the objection that multiverses are too weird makes no logical sense.