Re: Closer To Truth interview

On 9 May 2013, at 13:44, hibbsa <hibbsa-/[email protected]> wrote:

> --- In [email protected], David Deutsch <david.deutsch@...> wrote:
>> 
>> 
>> On 8 May 2013, at 22:23, Steve <sonatine123@...> wrote:
>> 
>>> Hello David
>>> 
>>> Thanks for this link - what an interesting website!
>>> 
>>> I have a question about one of your videos.  In 'Many Worlds Of Quantum Theory' you state a figure of 10 raised to 10 raised to the power of 23 as the number of histories involved when considering a cubic metre of air molecules.  How, in principle at least, is this figure derived ?
>>> 
>>> Incidentally I have read both of your books, and know a little about the 'Many Worlds Interpretaion' of quantum mechanics.
>> 
>> I can't remember the context in which I said that but it'll be something like this: 10^23 is the number of molecules in a mole (which actually occupies 22.4 litres, not a cubic metre, but never mind). If each molecule is in n different places at once, mostly uncorrelated with the others, then there are about n^(10^23) different histories under way. We can let n be 10 quite arbitrarily because with huge numbers like that, the topmost power is pretty much all that counts for purposes of envisaging it.
>> 
>> So it's a ballpark estimate raised to the power of a ballpark estimate raised to the power of a ballpark estimate.
>> 
> Why don't these histories become fungible on a higher level? 

It's because different-histories-becoming-fungibe is an interference phenomenon that requires 'fine-tuning' in the interaction. Assuming that the atoms in question start out un-entangled and with (say) approximately sharp positions and momenta and hence in approximately a single history, generic (non-fine-tuned) interactions will tend to entangle them more and more as they bounce around.

-- David Deutsch