On 6/27/2015 2:25 PM, John Clark wrote:
On Sat, Jun 27, 2015 meekerdb <[email protected] <mailto:[email protected]>>wrote: >> Conway's Life is computable but not predictable, > That raises a question as to what "predictable" means. If using the standard Game Of Life rules you could generate a new generational pattern in N steps but I had some magic algorithm that could do the same thing in less than N steps then the Game Of Life would be predictable. But there is no such algorithm. The fastest way to know what it would do is to just run the Game Of Life program and watch.
The same is true of most realistic problems in classical physics. Even though the theory is deterministic, evolution is unpredictable because (1) it can only be predicted numerically as an approximation to a continuum theory and (2) many systems are chaotic and sensitive to initial conditions and physical parameter values. I recently had a company that specializes in computational fluid dynamics compute a supersonic flow field around a fairly simple body. It took them a week to converge to a solution - and nobody thinks the solution is more than an approximation. Actual flow would have stabilized in milliseconds.
> In what sense is the evolution of Schrodinger's equation predictable? It doesn't matter because it described nothing observable, only the square of the absolute value ofSchrodinger's equation is important, and even then it's only a probability not a certainty. > the GoL is not reversible True, that's because for any given pattern there is usually more than one parent pattern that could have produced it. > if you watched a GoL running backwards it would include randomness. Yes, but a reverse Game Of Life is not computable.
True randomness is not computable by (at least one) definition of "random". But a good pseudo-random number generator would not be detectable for many steps (SFMT period = 2^216091).
Brent -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
