starship-design: Irrational Odds

[wharton@physics.ucla.edu (Ken Wharton)]

Isaac writes:

>>You can do an experiment of asking people how they're doing.  A
>>large portion of them will actually respond by saying "fine" or whatever,
>>even though the odds of everyone "randomly" behaving this way (and not
>>saying random words, clawing your eyeballs out, etc.) are inconceivable.
>>Every time you can even somewhat-accurately predict how someone will 
react
>>to a given set of circumstances, you are helping to refute the infinite-
>>universe possibility.
>
>Here you demonstrate how little you understand about probability and
>what it means to be a random event.
>
>Consider a hypothetical lottery which is randomly determined.  You
>buy one of those tickets.  Whether you win or not is random, and
>yet the most likely result is that you lose.  Just because something
>is random doesn't mean the chances are 50-50.
>
>Similarly, if you go up to John Smith and ask him how he's doing.
>Most of the time he'll say "fine".

Ahhh - but once you start thinking in terms of multiple universes, you lose 
the idea of probability.  What does it mean to have one universe that is 
less probable than another?  If a universe exists it's probability is one; 
the only probability involved is Which universe we happen to find ourselves 
in right now.  And that would mean that there have to be a lot of identical 
universes where John Smith says "fine" for every universe in which he says 
"hovercraft" just to make the odds turn out right. 

But that leads to more problems.  Suppose you have a quantum event that has 
a 1/pi chance of coming out A, and a (1 - 1/pi) chance of coming out B.  If 
the universe really splits off into alternate possible universes for each 
outcome, with each of the universes as "real" as the others, then there's 
no way to do it.  Even if you have lots of universes, because pi is 
irrational there's no way to make the odds come out correctly.  

I suppose it's still possible that nature has somehow "forced" all quantum 
probabilities to be rational numbers, so that the right number of universes 
can split off and still keep the correct odds, but this is getting ever 
more philisophically unwieldy.  All in all, I think this is a pretty strong 
argument for a single universe.


Ken