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Paradox disproves multiverse, says 9 year old.

  1. Dec 30, 2012 #1
    Hello everyone.

    My nine year old son and I were discussing the concept of the multiverse and he said this to me.

    "I can disprove the theory of the multiverse"
    "How?" I said
    "We'll, if there exists at least one universe for every possibility then there must be a universe where there isn't a multiverse! If there is a universe where there wasn't a multiverse then how was that universe created? It wasn't! Therefore it's a paradox!" He said confidently.

    I said it was a good point and said I would publish his theory on the forum. He said "ok!"

    The he went back to his Xbox.

  2. jcsd
  3. Dec 30, 2012 #2


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    Please convey our thanks for this contribution. :biggrin:
    I personally can say that (although I am very skeptical of multiworld ideas) I had never
    heard that line of reasoning aimed at disproving multiverse ideas by contradiction.
  4. Dec 30, 2012 #3
    Thanks Marcus,

    Nor me! And having thought about it I can't fault his argument. I too am skeptical of the multiverse idea as well.
  5. Dec 31, 2012 #4
    I've thought of several similar paradoxes and flaws.
    One of them is this:
    If there are infinite universes with all the infinite possibilities that can exist, that means there's a 0 dimensional universe where the entirety of infinite possibilities that exist in this dimension can fit on a finite piece of A4 paper, which folds into a paper aeroplane and throws itself.
    You, the universe, look down after you've been thrown and see a timeless view of every other possible universe, and whatever spawned the start of every universe (and before it).
    You decide to destroy the parent/host/system which generated you, because you can infinitely suck everything around your surface area into yourself, put it in a box then make it implode.
    I can imagine it, therefore it must be a possible universe that exists according to MWI, however illogical.

    I think in order for MWI to work, there needs to be a container in which it's restricted to changing infinitely.
    Perhaps it's only able to generate a universe due to different variations within the electromagnetic spectrum.
    The problem is if there is any structure to confine what the multiverse can create,
    How did this structure come into existence? And why is the apparatus of the way the multiverse produces more universes not generated/created in a way that would render something less functional all the time instead of the correct physical constraints that work?
    Last edited: Dec 31, 2012
  6. Dec 31, 2012 #5


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    Your son is certainly to be commended for his reasoning. But once some details about the multiverse hypothesis are considered, it's clear that such an argument doesn't apply.

    First, what physicists typically mean when they talk about the multiverse is not the "parallel universe" idea common to science fiction like Star Trek or Fringe. Rather, the multiverse is rooted in inflationary cosmology. In the multiverse scenario, different parts of the universe are allowed to inflate independently, possibly at different rates. The "bubbles" that subsequently form can be casually disconnected from each other and therefore observers in separate regions can't communicate with one another. In the cosmological parlance, they are separated by cosmic horizons. An observer within one of these horizons counts the space within the horizon as his "observable universe." The actual universe, which contains all of these regions, is then called the "multiverse", while the observable universe regions are called "universes." Obviously this nomenclature can be easily confusing when the details are lacking.

    The causual disconnect between universes makes it clear that the properties of a single universe can't have any effect whatsoever on the other universes. But it is also important to understand what physicists mean that was interpreted as "one universe for every possibility." The "possibilities" that are actually considered are fairly concrete. They are things like the physical constants: the gravitational constant, the fine structure constant, the masses of particles. etc. They can also involve some more complex features such as the structure of the gauge group of fundamental interactions. Basically what is allowed to vary between universes are the laws of physics and the parameters that appear in them. Existence of a multiverse is not the type of "possibility" that varies between universes. The existence of the multiverse is already the building block of the model, so it's assumed.

    Other types of possibilities, such as the existence of Leonard Nimoy (with or without sinister goatee) are also not considered. The anthropic principle so often applied to the multiverse is so far only concerned with the physical laws and whether or not nuclei, atoms and stars could have formed in such a way to allow any sort of human to exist in a given universe.

    It's certainly wise to be skeptical of the multiverse scenario. However, it's unlikely that it's possible to rule it out without having the correct "microscopic" description of the cosmological evolution of the universe. It's also probably good to note the difference between the multiverse concept and the anthropic principle usually applied to it. The latter might attract a larger amount of skepticism than is quite deserved by the former.
  7. Dec 31, 2012 #6


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    The argument falls apart right here. This just means that a "universe where there isn't a multiverse" doesn't fall within the realm of possibility if there is a multiverse. IOW, the existence of a multiverse excludes a universe without a multiverse as being a possibility. "Every possibility" does not mean "Everything is possible".
    For example, with a standard six sided die, rolling a "pi" is not a possibility.
  8. Dec 31, 2012 #7
    Tophness there seems to be a lot of interesting issues with the multiverse concept. You are right!

    Thanks for the kind words and explanation fzero, will reread your post to fully understand it.

    Thanks Janus, very interesting! So it's all possible states. Be interesting to hear opinions on what qualifies as possible in this context, especially the die analogy. Could there not be a universe where six sided dice produce other than the familiar numbers etc? Interesting to speculate. What is possible? Though I take your point regarding a universe where the multiverse doesn't exist may not be possible therefore is not a paradox.
  9. Jan 1, 2013 #8
    A die has a finite number of possibilities though. If it was an infinite-sided die that included decimal places, rolling pi would have to be a possibility. Including pi with an infinitely long decimal place.

    I agree that it doesn't mean everything is possible though.
    If the multiverse is the parent to a universe, then a 'universe without a multiverse' could only mean a strain of universe that isn't aware of the multiverse, and that the multiverse has a mechanism for making new universes that confine what can exist, because each universe has it's own 'bubble' that stops it effecting the mechanism or other universes.

    The problem with there being a mechanism or anything that restrains a universe from anything, is it leaves us with the same dilemma that the multiverse was supposed to solve - Who or what created it?
  10. Jan 2, 2013 #9
    As far as the dice are concerned, I was thinking along the lines that the laws of physics may well be different in different universes and thus the roll and out comes of six sided objects may be different to what we would expect in this universe, pi may well be different as well.

    The question regarding the non multiverse universe is whether this is actually a possibility or not, on the surface it seems not....but.....

    Either way for a nine year old I was impressed.
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