On 28 Oct 2012, at 18:51, John Clark wrote:

On Sun, Oct 28, 2012  Bruno Marchal <marc...@ulb.ac.be> wrote:

> Predicting the weather is hard, but in principle possible.

Quantum indeterminacy probably comes into play in long range weather predictions, but even if the world was as deterministic as Newton thought it was in the long run predicting what chaos will come up with is not possible even in principle.

OK.





We now know that computing or thinking is physical,


We don't know that. We deduce that in the Aristotelian's theories.



it takes energy to do it and it gives off heat;

Actually computation can be made reversibly, without dissipation of energy. There are reversible universal machine. This has been discovered by Wang, a logician, and rediscovered by some physicists much later. Only erasing information uses energy, and this is not needed for computation.




to predict what chaos will do you'd have to know the initial conditions with infinite (not just very good) precision and the computer would give off so much heat it would disturb the very thing you were looking at.

It's true that if you slow down any calculation you can perform it with a arbitrarily small amount of energy (and thus give off a arbitrarily small amount of heat) but it does no good to make a prediction about something that happened a billion years ago. Predicting the future is much more difficult than predicting the past.

> predicting the personal outcome of the self-duplication is easily show impossible in theory

If I knew that the environment would be Moscow I could say with 100% certainty that I will be the Moscow man, but for all I know it could be Duluth Minnesota or Austin Texas.

Not with the protocol given. It can only be Washington or Moscow.





> But if you agree that the self-duplication leads to indeterminacy [...]

Not any sort of indeterminacy that hasn't been well known for the better part of a century.

It is new, but this is another topic. If you accept it what is you opinion on step 4?

Bruno



  John K Clark




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