# Many worlds and "extreme" worlds

I assume there are worlds in the MWI where extremely improbable things (improbable according to our world) have happened repeatedly. Broken eggs reform themselves repeatedly etc... Will scientists in these worlds come up with the same laws of physics as this world? specifically the same laws of quantum mechanics? Assuming they follow the same scientific process we do...

How do we know we aren't in an "extreme" world? ie: How do we know our history of observations somehow matches the distribution of observations in different worlds...

• maybe it's best to let to (bad) SF the idea of infinite parallel worlds each changing by some detail. Or obviously it leads to various paradox like this one and others. Feb 16 '16 at 23:12
• MWI is a good lesson for what can happen when you don't just take one bad intellectual turn but several in a row... just like one of those unlikely worlds. :-) Feb 16 '16 at 23:52
• I don't understand why MWI fascinate so much people ! perhaps, this means that they feel something I don't ...
– user46925
Feb 17 '16 at 10:33

The way the MWI treats probability is roughly as follows. You take the non-probabilistic part of quantum theory. You then assign decision theoretic payoff to each possible measurement outcome and assign a value to a state that respects non-probabilistic axioms of decision theory. One example of such an axiom would be that if two states $|\psi_1\rangle,|\psi_2\rangle$ are the same except that every outcome has an increased payoff in $|\psi_2\rangle$ then the payoff for $|\psi_2\rangle$ is higher than that of $|\psi_1\rangle$. David Deutsch has explained that you can derive the standard probability rule given those assumptions. The MWI can be tested using those probabilistic predictions. If a particular event would make your theory problematic then an experimental observation of that event is a criticism of your theory.