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Many worlds many questions

  1. Apr 2, 2004 #1

    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 is trying to disprove the ‘many-worlds theory’ – I think the inspiration comes from the movie ‘Bounce’.

    I’ve been able to answer most of her questions, but some still puzzle me. Namely :

    *What experiment / finding would disprove the ‘many-worlds’ theory?

    *Is there any such research going on at the moment? &,

    *Which universities/institutions would most likely be researching in this area?

    There are a few more but these three are the main ones she is concerned with.

    I’ve started reading through these sites, but this area really isn’t my specialty so I’m finding it a little confusing:

    Any help that you could give will be most appreciated

    PS – If this has been posted in the wrong forum – please let me know which is the most appropriate one
    Last edited: Apr 2, 2004
  2. jcsd
  3. Apr 2, 2004 #2
    The many-worlds theory would be essentially impossible to disprove because it asserts the existence of a vast number of worlds that we cannot observe directly. Therefore, the fact that we don't observe them doesn't do anything to prove or disprove the theory. This is one of the principal objections of people who are against this interpretation of quantum mechanics.

    Having said that, there are some alternative approaches to QM that actually make predicitons that are different from the standard theory. Some hidden-variable and spontaneous collapse models are like this. An experiment showing that these are correct would not necessarily disprove many worlds, but would make it a lot less appealing.

    David Deutsch has argued that it is theoretically possible to prove the many worlds theory, if we could somehow undo the dynamics that caused the worlds to split. However, this would require a direct interaction across several worlds in the multiverse, so it is doubtful that it could ever be done. I have often speculated that it would take a very powerful (Maxwell's) demon* to achieve this. I am also not convinced that it would rule out all possible alternatives, although it would clearly rule out anything that includes wavefunction collapse as a real physical process.

    Most many-worlds research is pretty much all theoretical at the moment and any experimental test is far beyond our current understanding. There are several theoretical questions that need to be sorted out, such as how does probability enter into the interpretation and how does the universe decide how and when to do the splitting.

    The many-worlds advocate with the highest profile is probably David Deutsch at Oxford University in the UK. There are a few other people there also working on it. You might want to read his book "The Structure of the Multiverse" for more details. Another advocate that comes to mind is Lev Vaidman at Tel-Aviv university.

    It is worth noting that many worlds theory played a large part in the birth of quantum computing and quantum information theory. Many researchers in this field take the many-worlds interpretation seriously.

    I would also like to comment that it is probably not wise to take the "science" part of science-fiction too seriously. It is a good idea to draw inspiration from what scientists say, but a strict application of science would probably constrain the story far too much. For example, it is well known that Star Trek employ a science advisor to come up with fancy explanations, but even so, things like inertial dampers, replicators and transporters are ridiculous from a physics point of view.

    I recommend that your student picks up a copy of "Gnarl", a short story collection by Rudy Rucker. He employs the superposition principle in one story in a way that is not really physically accurate, but is probably a good example of the sort of thing your student wants to do. He also has a favourite time-travel paradox that he plays with in a couple of stories. It's a good example of modern sci-fi, but I should warn you that some of the other stories in the collection might be a bit risque depending on how liberal your school's attitude is to these things.

    * Maxwell's demon is also something you might want to look into as a device for making more than one world interact with each other. Wikipedia: Maxwell's Demon
  4. Apr 2, 2004 #3
    Rest assured that that one can simply state this:If the manyworlds do not exist, then we should have mirror copies of ourselves walking around in ourspacetime?..a Groundhog-Day nightmare scenario!

    One strong reason that there must be other 'worlds' is that we do not bump into ourselves in a 'yesterday' or 'Tomorrow', therfore the 'Present' is free of all our 'copies'. What we were doing 'Yesterday' is the realm of the many worlds scenarios.
  5. Apr 3, 2004 #4
    Thankyou slyboy and ranyart,

    I think Maxwells demon may be one of the things she was looking for. She was trying to ask a question about an entropy based effect but did not have the terminology to get her ideas across.

    Unfortunately (or fortunately), the requirements of the English curriculum require this task to have a significant link to reality - hence the need for the science fiction to be based on science fact. Whether this really means she needs to have accurate theoretical physics grounding, or just nice-sounding technobabble I do not know.

    There were a few more questions about tunnelling, worm holes and "ghost black holes?" but I'll have to find out exactly what she want to know before picking your brains some more.

    Thanks again
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