> On 5 Mar 2019, at 00:43, Brent Meeker <[email protected]> wrote: > > > > On 3/4/2019 3:54 AM, Bruno Marchal wrote: >> >>> On 3 Mar 2019, at 20:43, Brent Meeker <[email protected] >>> <mailto:[email protected]>> wrote: >>> >>> >>> >>> On 3/3/2019 4:52 AM, Philip Thrift wrote: >>>> >>>> >>>> Here's an example David Wallace presents (as an "outlandish" possibility): >>>> Suppose in pi (which is computable, so has a program (a spigot one, in >>>> fact) that produces its digits. Suppose somewhere in that stream of digits >>>> is the Standard Model Equation >>>> >>>> (say written in LaTeX/Math but rendered here) >>>> >>>> https://www.sciencealert.com/images/Screen_Shot_2016-08-03_at_3.20.12_pm.png >>>> >>>> <https://www.sciencealert.com/images/Screen_Shot_2016-08-03_at_3.20.12_pm.png> >>>> >>>> So what could this mean? (He sort of leaves it hanging.) >>>> >>> >>> Nothing. Given a suitable mapping the SM Lagrangian can be found in any >>> sequence of symbols. It's just a special case of the rock that computes >>> everything. >> >> Even if rock would exist in some primitive sense, which I doubt, they do not >> compute anything, except in a trivial sense the quantum state of the rock. A >> rock is not even a definable digital object. > > It's an ostensively definable object...which is much better.
Ostension is dream-able. > >> If someone want to convince me that a rock can compute everything, I will >> ask them to write a complier of the combinators, say, in the rock. I will >> ask an algorithm generating the phi_i associated to the rock. > > There is no particular phi_i associated to the rock. That's the point. The > rock goes thru various states so there exists a mapping from that sequence of > states to any computation with a similar number of states. It is a mapping of states. It is like a bijection. You need something like a morphism preserving the computability structure, which do not exist in the rock. A computation is not just a sequence of states, it is a sequence of states defined by the universal machine which brought those states. There are bijections between N and Z, but only Z is a group, because those bijections does not preserve the algebraic structure. Similarly, there is a bijection between a computation and a movie of that computation, but it does not preserve the causal/logical relation between the states, which is a universal machine for the computation, and just a linear order for the sequence, without structure, of the states. > Of course one may object that the actual computation is in the > mapping...but that's because of our prejudice for increasing entropy. OK.Now, a bijection between a physical computation and an arithmetical computation do preserve the computability structure, that is why we can say that the arithmetical reality/model implements genuinely the computations. Bruno > > 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] > <mailto:[email protected]>. > To post to this group, send email to [email protected] > <mailto:[email protected]>. > Visit this group at https://groups.google.com/group/everything-list > <https://groups.google.com/group/everything-list>. > For more options, visit https://groups.google.com/d/optout > <https://groups.google.com/d/optout>. -- 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 https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
