# Parallel Universe Theory -- Did I Understand This Correctly?

**URL:** <https://boards.straightdope.com/t/parallel-universe-theory-did-i-understand-this-correctly/475577>\
**Category:** Factual Questions\
**Created:** [December 3, 2008, 10:02pm UTC](https://boards.straightdope.com/t/parallel-universe-theory-did-i-understand-this-correctly/475577 "2008-12-03T22:02:18Z")\
**Posts on this page:** 2\
**Page:** 3

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**Author:** ![Indistinguishable](https://avatars.discourse-cdn.com/v4/letter/i/90ced4/32.png) [@Indistinguishable](https://boards.straightdope.com/u/Indistinguishable)\
**Post date:** [December 6, 2008, 9:46pm UTC](https://boards.straightdope.com/t/parallel-universe-theory-did-i-understand-this-correctly/475577/41 "2008-12-06T21:46:13Z")

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> [@Chronos](#):
>
> On the other hand, if I flip a _fair_ coin 1000 times in a row, and repeat the experiment in an infinite number of universes, then I must get 1000 heads in a row in some of them (in an infinite number, in fact). Why? Because if I didn’t, then the coin would not be fair, by definition.

This is an odd thing to say. If you can, with a fair coin, get 1000 heads in a row in an infinite number of universes, then, clearly, it’s possible to flip a fair coin 1000 times in an infinite number of universes and never get 1000 tails in a row (or even so much as a single tail).

The mainstream mathematical conception of probability would not require of fair coins the things you are requiring of them. Perhaps that only indicates that the mainstream mathematical conception of probability is not the most apt one, but there does appear to be some difficulty in making coherent the definition you are putting forth. [Not necessarily insurmountable difficulty, but it does require some care]

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**Author:** ![AllWalker](https://avatars.discourse-cdn.com/v4/letter/a/db5fbb/32.png) [@AllWalker](https://boards.straightdope.com/u/AllWalker)\
**Post date:** [December 7, 2008, 12:50am UTC](https://boards.straightdope.com/t/parallel-universe-theory-did-i-understand-this-correctly/475577/42 "2008-12-07T00:50:21Z")

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> [@AllWalker](#):
>
> Slight sidetrack, but here is a fun thought experiment
> 
> 1. Assume infinite number of universes, as with the many worlds interpretation
> 2. Assume travel between universes is possible - not even likely, just not outright impossible
> 3. So therefore, any scenario you can imagine occurs in some of the universes - like in the OP, we have Rhode Sea universes, or universes with life but no planets. In infinite Creation, it is all inevitable.
> 4. So therefore, in a different universe, a giant lizard opens a portal to our universe, comes through and declares underpants illegal. I imagined it, so it is possible, nay, inevitable.

All right, I’m going to give one of many solutions to this ‘paradox’. Yes, there is a problem with assumption #2. But even if you accept it as fact, it still breaks down at 4)

The problem with 4) is the phrase “our universe”. “Our universe” is as fluid a concept as “now”. The first utterance of which is different to this “now”. In the many worlds hypothesis, every event causes the universe to ‘split’ in order to allow all possible outcomes to occur. Thus, the lizard materialising is an event which causes ‘our universe’ to branch off. Thus, in the though experiment there would be a universe where everyone was forced to go commando. This universe would have been “our universe” up until that point. So the presence of underwear in “our universe” does not contradict either 1), 2) or 3).

But I’m disappointed by the lack of indulgence given. All I wanted was to ignore some boring little aspect of the laws of physics, people. I even asked nicely. 🙂

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