Dear Bruno, it is so fascinating to read about "universal machines". Is there a place where I could learn in short, understandable terms what they may be? Then again the difference between a 'Turing machine' and a 'physical computer' (what I usually call our embryonic Kraxlwerk). I grew up into my science without computers, got my doctorates in 1948 and 1967 and faced a computer first on a different continent (USA) in 1980. At that time I had already ~30 patents and a reputation of a practical scientist. So I need more than the 'difference' into the universal.
Descriptions I saw turned me off. My chemistry-based polymer science does not give me the base for most (and mostly theoretical!) descriptions. How'bout common sense base? John M On Thu, Mar 21, 2013 at 2:02 PM, Bruno Marchal <[email protected]> wrote: > > On 21 Mar 2013, at 02:32, Stephen P. King wrote: > > Are physical computers truly "universal Turing Machines"? No! They do not > have infinite tape, not precise read/write heads. They are subject to noise > and error. > > > > The infinite tape is not part of the universal machine. A universal > machine is a number u such that phi_u(x, y) = phi_x(y). > > Please concentrate to the thought experiments, the sum will be taken on > the memories of those who get the continuations, and the extensions. > > When a löbian universal number run out of memory, he asks for more memory > space or write on the wall of the cave, soon or later. And if it does not > get it it dies, but from the 1p, it will find itself in a situation > extending the memory (by just 1p indeterminacy). > > > Universal machines are finite entities. Physical Computer are particular > case of Turing machine, and can emulate all other possible universal > number, and the same is true for each of them. All universal machine can > imitate all universal machines. > But no universal machines can be universal for the notion of a belief, > knowledge, observation, feeling, etc. In those matter, they can differ a > lot. > > But they are all finite, and their ability is measured by abstracting from > the time and space (in the number theoretical or computer theoretical > sense) needed to accomplish the task. > > That they have no precise read/write components, makes them harder to > recognize among the phi_i, but this is not a problem, given that we know > that we already cannot know which machine we are, and form the first person > point of view, we are supported by all the relevant machines and > computations. > > And they are all subject to noise and error, (that follows from > arithmetic). Those noise and errors are their best allies to build more > stable realities, I guess. > > Bruno > > > > > http://iridia.ulb.ac.be/~marchal/ > > > > -- > 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?hl=en. > For more options, visit https://groups.google.com/groups/opt_out. > > > -- 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?hl=en. For more options, visit https://groups.google.com/groups/opt_out.
