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monkeywicked comments on Welcome to Less Wrong! (2012) - Less Wrong

25 Post author: orthonormal 26 December 2011 10:57PM

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Comment author: monkeywicked 25 June 2012 09:23:25PM 5 points [-]

Hi.

I'm a fiction writer and while I strive towards rationalism in my daily life, I can also appreciate many non-rational things: nonsensical mythologies, perverse human behaviors, and the many dramas and tragedies of people behaving irrationally. My criteria for value often relates to how complex and stimulating I find something... not necessarily how accurate or true it may be. I can take pleasure in ridiculous pseudo-science almost as much as actual science, enjoy a pop-science theory as much as deep epistemology, and I can find a hopelessly misguided person to be more compelling and sympathetic than a great rationalist.

However, conveniently, it often turns out that the most interesting stories, the most mind-bending concepts, and the most impressive acts of creativity are born of rationalist thinking rather than pure whimsy. And so I can have my cake and eat it too, because the posts at LW are as likely to create the sensation of mental expansiveness that I associate with great fiction (or, I suspect, compelling theology) while also attempting to be, uh, you know, less wrong.

So it's fun to be here. And if it helps me think and experience the world more clearly and critically... that's gravy.

Recently I've been working on several sci-fi writing projects that involve topics that are discussed at LW. One is about the development of AI and one about the multi-world interpretation. Neither project is 100% "hard sci-fi," however I would ideally like them to be not totally stupid... since I think plausibility and accuracy often produce narrative interest--even if plausibility and accuracy are not, in of themselves, objectives. After doing a lot of research on the topics, I still have many questions. It seems to me that the LW community might be the best place to get clear, smart, informed answers in layman's terms.

I'll fire away with a couple questions and see what happens. If this works out, I'll probably have a lot more...

(I wasn't sure if these ought to be a comments at And the Winner Is... Many World If so, I can re-post there.)

  1. In the MWI its often suggested that anything that could have happened will have happened. Thus, quantum immortality, etc. But this often puzzles me. Just because there are infinite worlds, why should there be infinite diversity of worlds? You could easily create infinite worlds by simply moving a single atom around to an infinite number of locations... but those worlds would be essentially identical. If Everett's chance of surviving each year is 100 - 1% for every year he lives, then wouldn't that mean his chance of being dead at 100 is 100%? Wouldn't that mean he's dead in all worlds? If you send an infinite number of light photons through the double slit their infinite possible locations on the wall are extremely limited. Couldn't the many worlds of the MWI resemble infinite photons being sent through the a double-slit experiment? Infinite in number, but extremely constrained in result?

  2. Is it possible, within the MWI, to have a situation where all but one world experiences some event? E.g. event X happens at time 2 in world 2, time 3 in world 3 and so on so that X appears at some time in every world except world 1. Now say that X is a Vacuum Decay event... wouldn't that mean it is possible to only have ONE viable, interesting world even within the MWI?

  3. David Deutsch, in The Fabric of Reality, claims that a quantum computer running Shor's Algorithm would be borrowing computational power from parallel worlds since there isn't enough computational power in all of our universe to run Shor's Algorithm. Does anyone know what would be happening in the worlds that the computer is borrowing the computational power from? Would those worlds also have to have identical computers running Shor's Algorithm? Or is there some more mysterious way in which a quantum computer can borrow computational power from other worlds?

  4. Is there any hypothetical, theoretical, or even vaguely plausible way for an intelligent being in one world to gain information about the other worlds in the MWI? Interference takes place constantly between particles in our world and other worlds; is there any way to for this interference to be turned into communication or at least advanced speculation about the other worlds? Or is such a notion pure fantasy?

Thanks in advance! If anyone can answer any of these or redirect me to resources inside/outside of LW, I'd be grateful.

Cheers,

MW

Comment author: pragmatist 25 June 2012 10:04:07PM *  3 points [-]

Welcome to LessWrong! Here are some answers to your questions about MWI:

  1. The space of possibilities in MWI is given by the configuration space of all the particles in the universe. The configuration space consists of every possible arrangement of those particles in physical space. So if a situation can be realized by rearranging the particles, then it is possible according to MWI. There is a slight caveat here, though. Strictly speaking, the only possibilities that are realized correspond to points in configuration space that are, at some point in time, assigned non-zero wavefunction amplitude. There is no requirement that, for an arbitrary initial condition and a finite period of time, every point in configuration space must have non-zero amplitude at some point during that period. Anyway, thinking in terms of worlds is actually a recipe for confusion when it comes to MWI, although at some level it may be unavoidable. The imporant thing to realize is that in MWI "worlds" aren't fundamental entities. The fundamental object is the wavefunction, and "worlds" are imprecise emergent patterns. Think of "worlds" in MWI the same way you think of "blobs" when you spill some ink. How much ink does there need to be in a particular region before you'd say there's a blob there? How do you count the number of blobs? These are all vague questions.

  2. MWI does not play nicely with quantum field theory. The whole notion of a false vacuum tunneling into a true vacuum (which, I presume, is what you mean by vacuum decay) only makes sense in the context of QFT. The configuration space of MWI is constructed by considering all the arrangements of a fixed number of particles. So particle number is constant across all worlds and all times in configuration space. Unlike QFT, particles can't be created or destroyed. So the configuration space of a zero-particle world would be trivial, a single point. If you have more than one particle then all the worlds would have to have more than one particle. None of them would be non-viable or uninteresting. Perhaps it is possible to construct a version of MWI that is compatible with QFT, but I haven't seen such a construction yet.

  3. Deutsch's version of MWI (at least at the time he wrote that book) is different from the form of MWI advocated in the sequences. According to the latter, "world-splitting" is just decoherence, the interaction of a quantum system with its environment. But a quantum computer will not work if it decoheres. So according to this version of MWI, in order for a quantum computer to work, we need to make sure it doesn't split into different worlds. Instead, we would have a quantum computer in a superposed state within a single world, which I guess you can think of as many overlapping and interfering computers embedded in a single larger world. So you're not really harnessing the computational power of other worlds.

  4. On an appropriate conception of "worlds", interference does not take place between particles in our world and other worlds. Interference effects are an indication of superposition in our world, a sign of a quantum system that hasn't decohered. Decoherence destroys interference. It is possible for there to be interference between full-fledged worlds (separate branches of a wave function large enough to contain human beings), but it is astronomically unlikely. You can communicate with other worlds trivially, as long as those worlds are ones which will split off from your world in the future. But otherwise, you're out of luck.

Comment author: monkeywicked 27 June 2012 09:00:46PM 0 points [-]

Thanks for the answers, Pragmatist. I'm still fairly confused. But I'll read more in the sequence and elsewhere. I appreciate the effort/time.

Comment author: Zack_M_Davis 25 June 2012 09:40:19PM *  1 point [-]

However, conveniently, it often turns out that the most interesting stories, the most mind-bending concepts, and the most impressive acts of creativity are born of rationalist thinking rather than pure whimsy.

Yes; I like Steven Kaas's explanation:

Truth is more interesting than fiction because it's connected to a larger body of canon.

Comment author: shminux 25 June 2012 10:08:37PM -1 points [-]

Is there any hypothetical, theoretical, or even vaguely plausible way for an intelligent being in one world to gain information about the other worlds in the MWI? Interference takes place constantly between particles in our world and other worlds; is there any way to for this interference to be turned into communication or at least advanced speculation about the other worlds?

I don't know of any models that propose a mechanism for such a communication (assuming you mean actually sending messages back and forth). A model like that would move the MWI from the realm of interpretations back into something testable. It would be way cool, of course, but don't hold your breath :)

Comment author: OrphanWilde 26 June 2012 03:56:52PM -1 points [-]

One thing about the MWI which confused me at first -

The MWI is not a single interpretation, contrary to the name. There are several different versions of MWI floating around.

I believe the original interpretation had the many worlds existing, but generally independent from one another; a single world represents multiple possible states, but as soon as a state is determined (whatever you want to call this process), the world becomes independent, and ceases to interact with the possible states which weren't realized in that world. (Although different books will tell you different things, this is, as far as I've been able to divine, the original one.) In the original version, worlds split, permanently, from one another. So there would be no way to communicate with them. I believe this is the version Yudkowsky follows.

I've seen references to arguments that the fifth-dimensional variant (where worlds coexist and overlap, implying that some communication is possible) is impossible, but I've never seen the arguments themselves, in spite of looking.