Do you know how to build a computer that expands with exactly the speed of light?
No. I have nothing more exotic to suggest than a spherical expansion of ultrarelativistic constructor fleets, building Matrioshka-brains that communicate electromagnetically. All I'm saying is, if you think you have an unbounded demand for computation, I see no computational reason to expand at anything less than the maximum speed.
we can't observe other civilizations because they are approaching us with the speed of light.
How do two such civilizations react when they collide?
I believe that time is an emergent phenomenon, and it is emerging from the more basic notion of memory.
Is "memory" a mathematical concept? We are talking about Tegmark's theory, right? Anyway, you go on to say
in our Universe, these processes typically are in sync
and the moment you talk about "processes", you have implicitly reintroduced the concept of time.
So you're doing several things wrong at once.
1) You talk about process as if that was a concept distinct from and more fundamental than the concept of time, when in fact it's the other way around.
2) You hope to derive time from memory. I see two ways that can work out, neither satisfactory. Either you talk about memory processes and we are back to the previous problem of presupposing time; or you adopt an explicitly timeless physical ontology, like Julian Barbour, and say you're accounting for the appearance of time or the illusion of time. Are you prepared to do that - to say simply that time is not real? I'll still disagree with you, but your position will be a little more consistent.
3) Finally, this started out in Tegmark's multiverse. But if we are sticking to purely mathematical concepts, there is neither a notion of memory or of process in such an ontology. Tell me where time or memory is in the ZFC universe of sets, for example! The root of the problem again is the neglect of representation. We use these mathematical objects to represent process, mental states, physical states and so forth, and then careless or unwary thinkers simply equivocate between the mathematics and the thing represented.
All I'm saying is, if you think you have an unbounded demand for computation, I see no computational reason to expand at anything less than the maximum speed.
I agree. That's why I was careful to ask the advice of physicists and not computer scientists. I am a computer scientist myself.
How do two such civilizations react when they collide?
I don't know. But these cyclic cellular automata were an influence when I was thinking about these ideas. http://www.permadi.com/java/cautom/index.html (Java applet)
...and the moment you talk about "processes&qu
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.)