## text ✓ Something Deeply Hidden uantum Worlds and the Emergence of Spacetime Ñ Sean Carroll

Een in crisis since 1927 uantum mechanics has always had obvious gaps which have come to be simply ignored Science popularizers keep telling us how weird it is how impossible it is to understand Academics discourage students from working on the dead end of uantum foundations Putting his professional reputation on the line with this audacious yet entirely reasonable book Carroll says that the crisis can now come to an end We just have to accept that there is than one of us in the universe There are many many Sean Carrolls Many of every one of us Copies of you are I think I can safely say that nobody understands uantum mechanics Richard Feynman Shut up and calculate David Mermin Sweet is by convention bitter by convention cold by convention color by convention; in truth there are only atoms and the void DemocritusAs an amateur I love physics I think there is something in my brain that associates the bleeding edge of physics with poetry and art I'm not the only one Authors like Thomas Pynchon and Cormac McCarthy are constantly using physics as a springboard into literary ideas and explorations I think one of the big connections between theoretical physics and literature is the fact that both seek to explain the world through imagery and metaphor Physics are hard science's poetsSean Carrol does a fantastic job of describing the many worlds interpretation MWI as initially suggested by Hugh Everett The entire price of admission to this book was paid when I discovered in this book that Hugh Everett is the father of EELS' lead singer and song writer Mark Oliver Everett also known as E Talk about convergenceAnyway the book was well written carefully laid out and like other topics I've flirted with Knot theory I'm pretty sure I just walked off with a pip of knowledge but I'll keep coming back to the damn fruit of the tree of knowledge

### doc Something Deeply Hidden uantum Worlds and the Emergence of Spacetime

Something Deeply Hidden uantum Worlds and the Emergence of SpacetimeGenerated thousands of times per second The Many Worlds Theory of uantum behavior says that every time there is a uantum event a world splits off with everything in it the same except in that other world the uantum event didn't happen Step by step in Carroll's uniuely lucid way he tackles the major objections to this otherworldly revelation until his case is inescapably established Rarely does a book so fully reorganize how we think about our place in the universe We are on the threshold of a new understanding of where we are in the cosmos and what we are made In this book Carroll fully embraces the reality of uantum mechanics He doesn’t accept that it’s just useful for calculations Carroll says that the uantum world is the real world Rather than proceed from classical physics to explain the uantum world Carroll starts with the uantum world to find out how it builds the world described by classical physics Carroll’s approach leads to what many consider outlandish conclusionsCarroll is a theoretical physicist at Caltech and an award winning author of physics books Here he makes a case for the Many Worlds theory of uantum mechanics calling it “the most promising formulation of uantum mechanics” uantum mechanics is proven science It is fundamental to the way the universe works But what it tells us about the nature of reality is disputed The different takes on this uestion have been commonly called interpretations but Carroll considers this term misleading since it implies the answer is subjective He uses the recent description the foundations of uantum mechanics Here I’ll stick with the familiar and less cumbersome word interpretationThe Many Worlds interpretation of uantum mechanics was first espoused in 1957 by physicist Hugh Everett in his PhD thesis under the guidance of Noble Prize winner John Wheeler The Many Worlds interpretation was at first widely dismissed as nonsense but has gained support over time In the uantum state particles are in superposition meaning they are in a combination of positions all at the same time both here and there an electron spinning both up and down a photon both vertically and horizontally polarized etc While strange we know it is true uantum computers are being built that operate taking advantage of those extra states to process calculations at unheard of speed Every uantum object has a wave function which tells us the probability of finding it in a particular state When we measure we get a distinct answer But what is the fundamental reality the uantum state of superposition or the measurement yielding a specific position? Carroll believes it is the uantum state The measurement is just what we observe This belief pits Carroll against the standard theory also known as the Copenhagen interpretation Carroll says the Many Worlds theory is consistent with the science while the traditional interpretation is not First Many Worlds avoids the measurement problem that plagues the Copenhagen interpretation The Copenhagen interpretation holds that the wave function collapses when we measure yielding a specific value Carroll holds there is no reason to believe that the wave function does collapse Physicists commonly accept that the evolution of the wave function is defined by Schrodinger’s euation That euation does not indicate the collapse of the wave function Nor is there any other support for the collapse According to Carroll it was just made up to explain why measurement gives a specific outcome An implication of the Copenhagen interpretation is that particles in the uantum world only become real when they are measured This makes no sense Carroll holds that all the possible outcomes are real but in different universes The Many Worlds theory holds that for every possible outcome the universe splits accommodating each Carroll believes there is one wave function for the universe and we are all in superposition with it So if we are betting on a coin toss in one universe we win but in another we lose We are entangled with the coin and go together in both universes each universe forever completely separate from the other A second problem with the Copenhagen interpretation is that it claims the uantum world only exits at the micro level of fundamental particles even though experiments now show that larger objects display uantum characteristics So where is the dividing line between where uantum mechanics rules and classical physics rules Any such line is arbitrary Carroll considers the entire universe to be part of the uantum world defined by a uantum wave function just as are fundamental particles He holds that the everyday world we encounter the universe described by classical physics is an emergent property of the universe’s wave function Carroll says that the Many Worlds interpretation best explains the reality of the uantum There is no measurement problem no arbitrary distinction between uantum and classical worlds and no mysterious making something real by measuring it Every outcome is real and consistent with the uantum worldCarroll points to entanglement an idea that came out of uantum mechanics that has been proven in experiments When two particles become entangled they become one uantum system a change in one means the other also changes instantaneously even if they are light years apart Carroll believes every object can become entangled For example the euipment or people measuring particles or anything else become entangled with them and also are in superposition with them Photons electrons or other particles will inevitably interact with a macroscopic object Thus macroscopic objects are necessarily entangled with their environment and thus with the entire universe and are part of its wave function The Many Worlds formulation also offers an explanation for the famous two slit experiment When electrons pass through both slits of the testing apparatus they hit a screen forming an interference pattern because they are waves But when we set up a detector to measure them they pass straight through to the screen showing up as if they were particles Carroll holds that this is because any interaction including measurement in this case between the detector and electron causes what is known in uantum mechanics as decoherence The electron’s uantum state has been altered In the Many Worlds theory decoherence causes the electron and its shared wave function with the universe to branch into different universes thus the electron can no longer interfere with itself as it passes through the detector Carroll briefly explores some alternative uantum theories the GRW theory of dynamical collapse the Bohmian mechanics model using pilot waves and Bism an epistemic model that holds the wave function is purely informational and not real Carroll sticks with Many Worlds calling it “simple and elegant” but indicates he will switch if something better comes along In the final chapters he explains uantum field theory describing uantum fields that fill the universe creating locality and becoming entangled In a fascinating discussion he shows how entanglement of uantum fields could yield space He also discusses the search for uantum gravity and looks at black holes from a uantum perspective These sections were uite involved but I enjoyed his uniue presentation Central to all of Carroll’s thinking is starting with uantum mechanics to create the world of classical physics In his own wordsNature is uantum from the start described by a wave function evolving according to an appropriate version of the Schrodinger euation Things like ‘space’ and ‘fields’ and ‘particles’ are useful ways of talking about that wave function in an appropriate classical limit We don’t want to start with space and fields and uantize them; we want to extract them from an intrinsically uantum wave functionFrom a Many Worlds perspective that treats uantum states as fundamental and everything else as emergent this suggests that we should really turn things around ‘positions in space’ are the variables in which interactions look local Space isn’t fundamental; it’s just a way to organize what’s going on in the underlying wave functionI don’t have any idea whether Many Worlds turns out to be a great contribution to physics or just a bizarre dead end But I don’t dismiss an idea just because it sounds crazy Regardless of the fate of Many Words I learned much about uantum mechanics from Carroll’s presentation For example he offered the clearest explanation I have read for why it is not possible to measure position and momentum at the same time in uantum mechanics I’ve read several of Carroll’s books and enjoyed them all In this one I found myself freuently paging back and forth It definitely is for someone with a strong interest in the subject and an open mind

### Sean Carroll Ñ Something Deeply Hidden uantum Worlds and the Emergence of Spacetime mobi

kindle ï Something Deeply Hidden uantum Worlds and the Emergence of Spacetime Ò Hardcover Ñ ❰PDF / Epub❯ ☉ Something Deeply Hidden uantum Worlds and the Emergence of Spacetime Author Sean Carroll – Gwairsoft.co.uk As you read these words copies of you areAs you read these words copies of you are being created Sean Carroll theoretical physicist and one of this world’s most celebrated writers on science rewrites the history of 20th century physics Already hailed as a masterpiece Something Deeply Hidden shows for the first time that facing up to the essential puzzle of uantum mechanics utterly transforms how we think about space and time His reconciling of uantum mechanics with Einstein’s theory of relativity changes well everything Most physicists haven’t even recognized the uncomfortable truth physics has b This book is about the Many Worlds hypothesis of uantum mechanics It is a deep description of the hypothesis and its context in uantum mechanics uantum mechanics does not violate logic; its precise predictions are correct and among the most accurate of any scientific theory But its foundations are still uite controversial especially when it comes to understanding the role of gravitation The Many Worlds hypothesis is a simple way to explain some of the seeming paradoxes of uantum mechanics There are alternative hypotheses and the book covers these as wellI can't say that I learned anything I am a physicist but the book did focus my attention on a few key ideas First it is incorrect to say that atoms are made up mostly of empty space; particles are not tiny points but are wave functions that are spread out in space Another example The Heisenberg Uncertainty Principle does not say that the act of measuring a uantity disturbs the system In addition it does not say that you cannot simultaneously measure position and momentum perfectly at the same time Instead it says that a definite position and momentum velocity do not even exist simultaneously The wave function solution to the Schrodinger Euation acts as a wave and so it can be analyzed like a Fourier Transform Think of a sudden audible transient like a click The click occurs at a definite point in time but it has no specific pitch because its spectrum is broadband Likewise a pure audible tone must occur over a span of time; it does not occur at a specific definite timeHere's the problem with the book Like many technical books that are aimed at non specialists it gets deep into jargon and concepts that are totally unfamiliar The non specialist can understand all the words and maybe even entire sentences But it comes off sounding like a foreign language And there is an additional problem with this book Much of the book focuses on the Schrodinger Euation which is a typical type of partial differential euation But unless you have studied similar euations you cannot really understand the physical concepts described in this book A general form of the euation is written in the book but it is so simplified that to a mathematician it doesn't convey much of anything and to a non mathematician it is gibberishThis book is an excellent attempt at explaining some of the deepest mysteries of uantum mechanics But the fundamentals are not covered well enough for a general reader to grasp all the arguments presented here