From: Osher Doctorow [EMAIL PROTECTED], Sat. Aug. 31, 2002 9:52PM Hal Finney, John Mikes, and the others on the parts of this thread that I have read have contributed some interesting ideas and questions.

I have not read the *time* articles in Scientific American, but I would like to put in a good word for at least the principle of inter-translating between quantitative and verbal languages, including the question of what to do about *rough* translations. Many quantitative people are very hesitant to publish in or contribute to the *popular* journals and literature including books and public-directed internet because they seem to feel that they would lose something important (*rigor*) in the translation and that their audience won't amount to *research material* anyway. I've taught mathematics/statistics and done research in mathematical physics and mathematical modeling at the college level (and occasionally Secondary levels) since the 1970s (I'm 63 years old), and I'm of the opinion that Creative Geniuses of the Leonardo Da Vinci and Pierre De Fermat level were verbal-quantitative geniuses (they happened to also be several hundred years ahead of their times, which is not quite true of many Nobel Prize winners). I would also say that Kurt Godel, Paul Dirac, Steven Weinberg (well, until recently anyway), Lord Francis Bacon, Shakespeare, Bach, Beethoven, Mozart, Vivaldi, Cervantes, Erwin Schrodinger, Einstein, G. 't Hooft, and Socrates especially reveal strong verbal-quantitative Creative Genius abilities and skills. In the process of translating back and forth between verbal and quantitative modalities, one stimulates associations and memories and ideas in both types of memory storage, and they seem to influence each other into further combinations and ideas. Largely because of this, I consider that it is better to translate *roughly* than not at all, and that if the main idea is conveyed, the details can wait to some extent for later if ever - the main ideas may well contribute to someone's Creativity. Scientific American and also various internet forums and discussion groups have done that mostly, and I like to point out that good side to them. I also think that the tendency to label *time* schools by individuals' names would better be changed to describing time schools by brief labels as to what they do. For example, *computer-time* versus *no special time-orientation* hardly seems a basis for categorizing time, although they could well contribute to some other categorization of time or something else. For myself, I think discrete versus continuous time and spacelike vs non-spacelike (in the sense of the 3+1 labellings vs the 4-dimensional ideas which just regard time as another spacelike axis or dimension) are more useful. Of course, it is interesting to ask how computers relate to time - and I think that we will eventually have to tackle the question of how quantum computers and analog computers for example differ from digital computers on this question. Osher Doctorow Ph.D. One or More of California State Universities and Community Colleges ----- Original Message ----- From: "Hal Finney" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Saturday, August 31, 2002 2:25 PM Subject: Re: Time > John Mikes writes: > > would it be too strenuous to briefly (and understandably???) > > summarize a position on time which is in the 'spirit' of the > > 'spirited' members of this list? > > It seems to me that there are two views of time which we have considered, > which I would classify as the Schmidhuber and the Tegmark approaches. > In the Schmidhuber view time is of fundamental importance, and in the > Tegmark view it is basically unimportant. > > Schmidhuber models the multiverse as the output of a computational > process operating on all possible programs. Since computation is > inherently sequential, it imposes a time ordering on the output. It is > natural to identify the time ordering of a computation with the time > ordering of events in our universe. So the simplest interpretation of > the Schmidhuber model as an explanation of our universe is to picture > the computer as generating successive instants of time as it operates. > > An obvious problem with this is that time appears to have a more > complex structure in our universe than in the classical Newtonian > block model. Special relativity teaches us that simultaneity is not > well defined. And general relativity even introduces the theoretical > possibility of time loops and other complex temporal topologies. It > is hard to see how a simple interpretation of Schmidhuber computation > could incoporate these details. > > Stephen Wolfram considers some related issues in his book, A New Kind > of Science. He is trying to come up with a simple computational model > of our universe (not of the multiverse, but the same issues arise). > In order to deal with special relativity he shows how a certain kind of > computational network can have consistent causality even when some parts > of the computation are run in advance of other parts. In other words, > simultaneity is not well defined in these models and it is possible > for different observers to have different ideas about simultaneity. > But the causality is the same for everyone. > > The other main model we have considered for the multiverse is that of > Tegmark, who identifies the universe with all possible mathematical > structures. In this model our universe is merely a complicated > mathematical object. The fact that we observe three dimensional space and > one dimensional time is due to the internal structure of the particular > mathematical object that we live in. Since all possible mathematical > structures exist, there would be other universes with one dimensional > space and three dimensional time, for example, along with an infinite > number of others. > > In this model, then, time is unimportant; it is merely an incidental > internal feature of certain mathematical constructs. Then we can > invoke the anthropic principle to say that mathematical objects which > have an internal time dimension can also lead to evolution, which can > lead to life like ours. So we have an explanation of time as being a > constraint on those mathematical objects which can include what Tegmark > calls self-aware subsystems, i.e. observers like ourselves. > > A final note, I think the Schmidhuber model can be approached in > a way more consistent with Tegmark by interpreting the output of a > computation as a structured object independent of the time ordering > used by the computation that created it (Wolfram pursues this idea in > his models as well). Looking at this document, for example, you read > it sequentially from top to bottom; but I didn't write it that way, > I rearranged some paragraphs and went back and did some edits here and > there before sending it. The document's internal structure imposes or > reveals an ordering that is independent of the way it was created. > > In the same way, Schmidhuber's programs can create universes, some of > which might then be interpreted to have an internal time dimension > similarly to how Tegmark's mathematical objects do. We would then > invoke the anthropic principle, as in the Tegmark case, to limit our > attention to Schmidhuber programs that produce output with an internal > time dimension that allows for conscious observers. > > Hal Finney >