What is Many worlds: Definition and 133 Discussions

The many-worlds interpretation (MWI) is an interpretation of quantum mechanics that asserts that the universal wavefunction is objectively real, and that there is no wavefunction collapse. This implies that all possible outcomes of quantum measurements are physically realized in some "world" or universe. In contrast to some other interpretations, such as the Copenhagen interpretation, the evolution of reality as a whole in MWI is rigidly deterministic. Many-worlds is also called the relative state formulation or the Everett interpretation, after physicist Hugh Everett, who first proposed it in 1957. Bryce DeWitt popularized the formulation and named it many-worlds in the 1960s and 1970s.In many-worlds, the subjective appearance of wavefunction collapse is explained by the mechanism of quantum decoherence. Decoherence approaches to interpreting quantum theory have been widely explored and developed since the 1970s, and have become quite popular. MWI is now considered a mainstream interpretation along with the other decoherence interpretations, collapse theories (including the Copenhagen interpretation), and hidden variable theories such as Bohmian mechanics.
The many-worlds interpretation implies that there are very many universes, perhaps infinitely many. It is one of many multiverse hypotheses in physics and philosophy. MWI views time as a many-branched tree, wherein every possible quantum outcome is realised. This is intended to resolve some paradoxes of quantum theory, such as the EPR paradox and Schrödinger's cat, since every possible outcome of a quantum event exists in its own universe.

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  1. F

    Is MWI Self-Contradictory and Does Time Travel Need a New Approach?

    I create this thread to discuss the different objections to MWI. Hopefully creating some interresting debate. First I'd like to start with the Born Rule. What are the views of proponents and opponents of MWI on this?
  2. J

    Many worlds and probability amplitude. What does it represent?

    Is there any statement which perfectly captures what the probability amplitude, in the many worlds interpretation, represents? To say that there is an x chance of y happening is non-sensical because, according to the interpretation, y WILL happen in at least one universe. To say that there is...
  3. Demystifier

    Observational evidence for many worlds (by Don N. Page)?

    In a recent paper http://xxx.lanl.gov/abs/1101.1083 Don N. Page presents a very interesting statistical anthropic argument for the reality of many worlds. It is not only an argument against the collapse hypothesis, but also against (my favoured) Bohmian interpretation. What do you think?
  4. I

    Possible argument in favor of many worlds interpretation

    Please forgive me if I am hideously wrong in any of my points. I am not terribly well-versed in quantum physics. Alright. This all began when I was thinking of a somewhat speculative and arguably philosophical idea that probably wouldn't have much of a place on this forum. My train of...
  5. J

    The Many Worlds Theory and Immortality

    Forgive me if I have not grasped the ideas and intricacies of the Many Worlds theory. If I don't quite understand it all it's probably because I'm 16. :bugeye: My theory goes like this: According to the many worlds theory, every time a sentient being observes the outcome of the a particle in...
  6. T

    Difference betweem Many Worlds and Consistent Histories?

    Can some help me out? It seems both postulate: Ontological wavefunction of the whole universe No collapse Both are deterministic Both use decoherence So what's different about them?
  7. U

    Many Worlds and the arrow of time

    I had a couple of interesting thoughts today on the matter of Many Worlds. First is that, in a way, I think the so-called "branching" posited for MWI could be thought of as a derivative of time. For example, time is the derivative of space (i.e. using change in space with respect to time)...
  8. rrw4rusty

    Questions on Many Worlds Interpretation

    Hi! I've seen videos depicting the ‘Many Worlds Interpretation’ of quantum physics which show T-Rex stomping through your living room because the K2 Event didn’t take place in that parallel universe, you know the hype you see on the MWI. While probably, no one ‘really’ thinks this is...
  9. rrw4rusty

    Questions on the test that led to Many Worlds

    Hello, This concerns the test where you have a barrier with two slits cut out of it, set in front of a wall or blackboard (or something that will show hits upon it) and devices that will shoot sub-atomic particles. My understanding is this: when particles are shot into the barrier with two...
  10. T

    Many worlds / parallel universes & improbable events

    Hi, I'm hoping that someone can explain one problem I have with the many worlds theory. If the many worlds theory is true, then we are currently living in a universe which is the product of an infinite number of splits in the past. Thus, looking at our history, we should have numerous...
  11. U

    Postulates of many worlds interpretation of QM

    I am interested to see a clear enumeration of the postulates of this interpretation. There seem to be something fuzzy about how MWI describes what we call "reality". It might be a problem with the theory or, more probable, a misunderstanding of my part. Here is a list I found on Google...
  12. D

    How does Many Worlds theory explain Schroedinger's cat

    As I understand it, when Schroedinger's "box" is opened, then a dead cat comes into existence in one universe and a live cat in another. However, in a variation to this experiment, in which there is say a 10% chance of the cat living and 90% dying, when the box is opened does one live cat come...
  13. F

    Many Worlds Theory: Separating Physically or Superimposing?

    In the many worlds theory when universes split off from one another, do they actually separate physically, or are they merely superimposed on each other, but unable to have an effect on each other? And if they separate from each other physically where do they go?
  14. C

    Help wanted in understanding many worlds theory

    Hi Can anybody direct me to a full explanation of the many-worlds theory, as proposed by Hugh Everett to replace the Copenhagen interpretation of quantum physics? I'm looking for something comprehensible to a layman, not too heavy on the maths if possible. Specifically, I wish to...
  15. W

    Could ghosts be explained by the many-worlds theory?

    Hi everyone I'm new here--a first year penn state undergrad--and the extent of what i know is the popularizations of quantum physics, so i might be a little off base, and I know that what I'm about to ask is borderline unscientific, but here goes Everett wrote his theory of the many-worlds...
  16. J

    Many Worlds experimental evidence

    I keep hearing that the "many worlds interpretation" is experimentally different than the collapse theories. But I haven't heard of anything other than "quantum suicide". Is there anything else? As far as quantum suicide, I fail to see how this differs from collapse theories. Isn't each...
  17. pellman

    Many Worlds Interpretation: Does Quantum Mechanics Work This Way?

    Suppose there is a quantum observable that can take two values, A or B. If a state is prepared that it is a superposition of the states A and B, then if I make an observation, according to many worlds interpretation, there will then be a superposition of two me's, one that observed A and one...
  18. A

    Can Artificial Consciousness Create an Entire Society Using Quantum Computers?

    Anyone know anything about creating artificial consciousness through the blueprints of people's consciousness, thus creating an artificial society. Through this you can predict how people will interact in an environment through social simulations and manipulate them. Through quantum...
  19. B

    IQ 195 Genius Challenges the Many Worlds Interpretation

    Earlier today, I saw a show that had the smartest man in America with an IQ of 195 who is working on a Cognitive - Theoretic Model of the Universe. He attacks the MWI with: What do Many-Worlders think about a statement such as this coming from an intelligent person?
  20. H

    Relative-state or many worlds theroy

    I am greatly interested in everything this theory holds, more out of interest and curiously then how relative or correct it may be. And as i do this research on my own i find that on my own i stay:rolleyes: lol. Many worlds theory is just a topic for when I'm in solitude, family and friends find...
  21. R

    Many Worlds Interpretation Experiment

    I recently learned about the Many Worlds Interpretation of quantum mechanics from another post on this forum. Unfortunately, the post became more of an argument about whether some experiment had or hadn't proven this interpretation to be true, and there wasn't a whole lot of information on what...
  22. T

    Consciousness, Determinism and the Many Worlds view

    There are a few threads about determinism here and a few about interpretations of quantum mechanics, so I thought I'd start one that combines them. Determinism is nicely defined by the Stanford Encyclopedia of Philosophy as: Ref: http://plato.stanford.edu/entries/determinism-causal/"...
  23. T

    Where does the energy come from to create new worlds in Many Worlds theory?

    My understanding of this theory is that instead of a superposition of states (for example, the Dead/Alive Cat in the box) you have two Universes, created from one, each satisfying one of the two outcomes (Dead cat in Universe 1, Live cat in Universe 2). It is also my understanding that...
  24. T

    Many Worlds Interpretation justifies Selfishness

    I wasn't sure where to put this thread because it is about moral philosophy but depends on your understanding of quantum mechanics. I'll try to keep quantum mechanics out of it and just explain what results from the Many Worlds Interpretation (MWI) of what's happening in quantum mechanics (QM)...
  25. B

    Many Worlds and Personal Immortality

    "Many Worlds" and Personal Immortality Let's say that the "many worlds" interpretation of quantum theory is correct. Let's also say that there is no afterlife, and that at death consciousness would simply end. So no one will ever experience anything after death. From the timeline of any...
  26. B

    Many Worlds Interpretation of SR

    Special Relativity predicts that moving clocks run slow, mass and length are variable and simultaneity is relative. These are 'real' phenomena and leads me to think that the reality of one observer (the passing of time, all physical properties and space-time events) can be regarded as 'his...
  27. M

    Question about the Many Worlds Interpretation

    I was learning about the "Many Worlds" interpretation of QM, and it got me to thinking. In some ways, doesn't it contradict the laws of thermodynamics? I came up with the following thought experiment: Suppose that you had a gas containing nitrogen and oxygen in a homogeneous mixture, in a...
  28. C

    Question About Many Worlds Interpretation

    After having researched on many different Websites the Many Worlds Interpretation of Quantum Mechanics, it seems to me as if there are two positions defended by physicists: Position 1: All the outcomes of a system actually happen in reality. That is, every time a choice is made all possible...
  29. V

    Is the Born rule a necessary postulate in Many Worlds theory?

    There's an interesting text on Many Worlds, http://www.anthropic-principle.com/preprints/manyworlds.html and I'd like to discuss it. There are 2 aspects with many worlds that I do not fully grasp. The first one, the more technical one, is how the correct probabilities emerge in MW. But...
  30. S

    Copenhagen & Many Worlds Falsified?

    Professor John Cramer, author of the transactional interpretation of QM, recently gave a talk at Boskone, the famous science fiction con, that sugggests a new experiment may be about to falsify the predictions of the Copenhagen and Many Worlds interpretations(and also decoherence and Consistent...
  31. T

    Can Experiments Disprove the Many-Worlds Theory?

    Hi, I’m a science teacher at a small, country high school in Australia. A student has recently come to me for assistance in writing her major English project – a science fiction story – because she needs to add some realism to her descriptions. The basis of the story is a scientist who...
  32. P

    Many Worlds Theory: What is it & is it True?

    Greetings forum experts. What is the Many Worlds theory? And, is there any evidence to suggest that it is wholly or partially correct? Thanks
  33. wasteofo2

    Simple contradiction/flaw in many worlds theory/theory explanation.

    As it's simply explained, the many worlds theory states that everything has an infinite amount of possible outcomes and that a new reality is created in which one of each outcome occurs. This process of new reality creation keeps occurring infinately, creating more and more infinite amounts of...
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