What is the optimal expansion speed of your computer
I see no reason to go slow on the expansion except for the possibility of hostile opposition. If you do intend to expand, you have nothing to gain computationally by delaying.
Of all the possible Universes in Tegmark's level IV Multiverse, most don't even have a concept of Time. How can we decide whether or not a specific Universe is in fact a Space-Time Continuum?
You have to build time into your metaphysics from the beginning. If you restrict your studies to arithmetic, category theory, or any study of static timeless entities, you won't get time back for free. In general relativity, to have a timelike direction, your metric must have a certain signature. So perhaps we can say that the "mathematical object", 4-manifold with a metric whose signature is +++- everywhere, describes a universe with time. But the mathematical object itself does not intrinsically contain time.
This is a significant flaw in Tegmark's scheme, as he describes it, as well as all belief systems of the form "reality is mathematics": mathematics is not the full ontology of the world. Time might be the least disputable illustration of this. Time is something you can describe mathematically, but it is not itself mathematics in the way that numbers are.
Let's consider a classic example of an ontology, Aristotle's. I mention it not to endorse it but simply to present an example of what an ontology looks like. According to Aristotle's ontology, everything that is belongs to one of ten classes of entity - substance, quantity, quality, relation, place, time, position, state, action, affection - and these entities connect to each other in specific ways, e.g. substances have qualities.
General ontological theory talks about these ten categories and their relationships. All lesser forms of knowledge are "regional ontologies", they only talk about subtypes of being, or perhaps beings which are built up from elementary types in some way.
Now Pythagoreans supposedly believed that all is number. If we transpose that slogan into Aristotle's categories, what is it saying? It's saying that the category of quantity is the only real one and the only one we need to study. Obviously an Aristotelian would reject this view. Quantity is not only to be studied in itself, but in its relations to the other categories.
Tegmark, and all other mathematical neoplatonists, are doing the same thing as the Pythagoreans. Modern mathematics is part of the full ontology, but only part of it. Because we know how to reason rigorously and with clarity about mathematical objects, and because we can represent so much of reality mathematically, there is apparently a temptation to view mathematics as reality itself. But this requires you to ignore the representation relation - what exactly is going on there? It's not as if anyone has a very convincing account of how things and their properties are fused into one. But to adopt mathematical neoplatonism guarantees that you will be unable to think straight about such issues. With respect to time, for example, you will inevitably end up skipping back and forth between rigorous discussion of the properties of semi-Riemannian metrics, and then vague or even bogus assertions about how the metric "is time" and so on. This vagueness is a symptom of a problem overlooked, namely, what is the larger ontology of which mathematics is just a subset, and how do the categories of mathematics relate to the more physical categories of reality, like time and substance?
There's no reason why you can't have a systematic multiverse theory based on a richer ontology, one with physical categories as well as mathematical. But you would have to figure out the outlines of that richer ontology first.
I see no reason to go slow on the expansion except for the possibility of hostile opposition. If you do intend to expand, you have nothing to gain computationally by delaying.
I am not sure. The laws of thermodynamics may interfere. Do you suggest that the optimal expansion speed I am looking for is equal to the speed of light? Do you know how to build a computer that expands with exactly the speed of light?
If you do, then I am very interested, because that makes a pet theory of mine work: I seriously believe that the expansion speed of (expanding) civil...
We have recently obtained evidence that a number of people, some with quite interesting backgrounds and areas of expertise, find LessWrong an interesting read but find limited opportunities to contribute.
This post is an invitation to engage, in relative safety but just a little beyond saying "Hi, I'm a lurker". Even that little is appreciated, to be sure, and it's OK for anyone who feels the slightest bit intimidated to remain on the sidelines. However, I'm confident that most readers will find it quite easy to answer at least the first of the following questions:
...and possibly these follow-ups:
Comments like the following, from the "Attention Lurkers" thread, suggest untapped resources:
My own area of professional expertise is computer programming - perhaps one of the common sub-populations here. I'm also a parent, and have been a beneficiary of prenatal diagnosis (toxoplasmosis: turned out not to be a big deal, but it might have been). My curiosity is often engaged by what goes on "behind the scenes" of the professions I interact with as an ordinary citizen.
Yes, I would be quite interested in striking up a conversation about applying the tools discussed here to prenatal diagnosis; or in a conversation about which conceptual tools that I don't know about yet turn out to be useful in dealing with the epistemic or ethical issues in prenatal diagnosis.
Metaphorically, the intent of this post is to provide a marketplace. We already have the "Where are we?" thread, which makes it easier for LessWrongers close to each other to meet up if they want to. ("Welcome to LessWrong" is the place to collect biographical information, but it specifically emphasizes the "rationalist" side of people, rather than their professional knowledge.)
In a similar spirit, please post a comment here offering (or requesting) domain-specific insights. My hunch is, we'll find that even those of us in professions that don't seem related to the topics covered here have more to contribute than they think; my hope is that this comment thread will be a valuable resource in the future.
A secondary intent of this post is to provide newcomers and lurkers with one more place where contributing can be expected to be safe from karma penalties - simply answer one of the questions that probably comes up most often when meeting strangers: "What do you do?". :)
(P.S. If you've read this far and are disappointed with the absence of any jokes about "yet another fundamental question", thank you for your attention, and please accept this apophasis as a consolation gift.)