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April 27, 2008

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Speaking of the Big Bang, after being reminded of a question elsewhere I'm curious as to whether people knowledgeable of it can evaluate my interpretation of it here.

I don't yet see how the possible existence of "duplicates" of me 10^(10^29) (is this different than 10^30?) light years away or "decohered amplitude-blobs of me" has an effect on my subjective conscious experience. Is the known/extrapolatable universe 10^(10^29) years old? That sounds a bit older than popularly presented ages of the universe.

It sounds like you're writing that these "duplicates" have no effect on our subjective conscious experience. And that does seem to me to be the case (I assume "decohered amplitude-blobs of me" are likely being tortured, but I don't seem to be experiencing it), although I think a lot more rigorous exploration may be required.

I'm wary, Eliezer, about you moving from "hey we know this thing about quantum mechanics and cosmology" to "hey, we can be confident that the subjective conscious experience won't be lost post-cryonics or uploading". It's good news if it's true, but I'm concerned by (1) lack of expert consensus on this, and (2) at a gut/intuitive level I sense cues that you want to believe this separate from what the best empiricism tells us, which may simply be that we don't know yet.

You also get the same Big World effect from the inflationary scenario in the Big Bang, which buds off multiple universes. And both spatial infinity and inflation are implied by the Standard Model of physics.

How exactly do you get spatial infinity from a big bang in finite time? The stories I hear about the big bang are that the universe was initially very, very small at the beginning of the big bang. If it was small then it was finite. How does an object (such as the universe) grow from finite size to infinite size in finite time?

It's not known whether the Universe is finite or infinite, this article gives more details:

http://en.wikipedia.org/wiki/Shape_of_the_Universe

If the Universe is infinite, then it has always been so even from the moment after the Big Bang; an infinite space can still expand.

It hadn't quite sunk in until this article that looked at from a sum-over-histories point of view, only identical configurations interfere; that makes decoherence much easier to understand.

Maybe later I'll do a post about why you shouldn't panic about the Big World. You shouldn't be drawing many epistemic implications from it, let alone moral implications. As Greg Egan put it, "It all adds up to normality." Indeed, I sometimes think of this as Egan's Law.
While I'm not currently panicking about it, I'd be very interested in reading that explanation. It currently seems to me that there should be certain implications, e.g. in Quantum suicide experiments. If mangled worlds says that the entity perfoming such an experiment should not expect to survive many iterations, that doesn't solve the space-like version of the issue: Some of the person's alternate-selves on far away alternate-earths would be prevented from carrying out their plan by weird stuff (TM) coming in from space at just the right time.


Hopefully Anonymous asked:

10^(10^29) (is this different than 10^30?)
It's different by a factor of roughly 10^(10^29). Strictly speaking the factor is 10^(10^29-30), but making that distinction isn't much more meaningful than distinguishing between metres and lightyears at those distances.

Sebastian, so 10^30 is 10 with 30 zeros after it. 10^10^29 is 10 with zillions of zeros after it. Thanks for making that clear.

Eliezer, I think your usage of "Standard Model" is different from that of physicists.

Quantum suicide is a good way to ensure that your next experience will be the trivial "experience" of being a corpse with no brain activity.

So what you're saying is that God does not play dice, and that frequentism is fundamentally true.

I think this has been the best post so far. I'd like to answer one of my previous questions to make sure I am grokking this; please weigh in if I am off. Here was my question:

Q: Am I correct in assuming that [the amplitude distribution] is independent of (observations, "wave function collapses", or whatever it is when we say that we find a particle at a certain point)?


A: As I suspected, a bit of a Wrong Question. But yes, there is only one amplitude distribution that progresses over time


Q: For example, let's I have a particle that is "probably" going to go in a straight to from x to y, i.e. at each point in time there is a huge bulge in the amplitude distribution at the appropriate point on the line from x to y. If I observe the particle on the opposite side of the moon at some point (i.e. where the amplitude is non-zero, but still tiny), does the particle still have the same probability as before of "jumping" back onto the line from x to y?


A: As was mentioned to me when I first asked this question, the probability of me observing the particle "jump back" is near-zero. When (I think) I realize now is that the reason this is true is that

[Brain being in a state where it remembered particle on the moon 1 second ago] * [Brain being in state where it sees particle "back" on the original line]

is close to zero. (This is of course ignoring the fact that there is no such thing as "this particle" vs "that particle". I'm pretending this is a new class of particle of which there is only one in the universe. Or something).


BTW, are you going to cover why the probability of a configuration is the square of its amplitude? Or if that was somehow already answered by the Ebborians, could I get a translation? :)

"And both spatial infinity and inflation are standard in the current model of physics."

As mentioned by a commenter above, spatial infinity is by no means required or implied by physical observation. Non-compact space-times are allowed by general relativity, but so are compact tori (which is a very real possibility) or a plethora of bizarre geometries which have been ruled out by experimental evidence.

Inflation is an interesting theory which agrees well with the small (relative to other areas of physics) amount of cosmological data which has been collected. However, the data by no means implies inflation. In fact, the term "inflation" refers to a huge zoo of models which have many unexplained parameters which can be tuned to fit the date. Physicists are far from absolutely confident in the inflationary picture.

Furthermore, there are serious, serious problems with Many Worlds Interpretation (and likewise for Mangled Worlds), which you neglect to mention here.

I enjoy your take on Quantum Mechanics, Eliezer, and I recommend this blog to everyone I know. I agree with you that Copenhagen untenable and the MWI is the current best idea. But you talk about some of your ideas like it's obvious and accepted by anyone who isn't an idiot. This does your readers a disservice.

I realize that this is a blog and not a refereed journal, so I can't expect you to follow all the rules. But I can appeal to your commitment to honesty in asking you to express the uncertainty of your ideas and to defer when necessary to the academic establishment.

"But you talk about some of your ideas like it's obvious and accepted by anyone who isn't an idiot. This does your readers a disservice.

I realize that this is a blog and not a refereed journal, so I can't expect you to follow all the rules. But I can appeal to your commitment to honesty in asking you to express the uncertainty of your ideas and to defer when necessary to the academic establishment."

Eliezer this is really great advice. Please take it.

Jess Reidel: I enjoy your take on Quantum Mechanics, Eliezer, and I recommend this blog to everyone I know. I agree with you that Copenhagen untenable and the MWI is the current best idea. But you talk about some of your ideas like it's obvious and accepted by anyone who isn't an idiot. This does your readers a disservice.

I realize that this is a blog and not a refereed journal, so I can't expect you to follow all the rules. But I can appeal to your commitment to honesty in asking you to express the uncertainty of your ideas and to defer when necessary to the academic establishment.

I mentioned the fact that there were problems with mangled worlds, but admit that I didn't mention what they were (e.g., seeming to predict that we should find ourselves in a very high-entropy world). In fact, the probability I assign to mangled worlds is below 50% - I just think it is a beautiful exemplar of what a non-mysterious explanation should look like. I'm sorry if this is not clear; I should make that point in an upcoming post explicitly about the Born probabilities.

The main problem with MWI is the Born probabilities - which I did mention, at length. I am not aware of any serious problems with MWI besides the Born probabilities. I will discuss continuity and choice of basis in upcoming days.

I will attempt to establish in upcoming posts that all remaining quantum theories worthy of being taken seriously are many-worlds theories. Hidden variables are experimentally disproved; quantum collapse is unphysical. The non-many-worlds theories are not just wrong, they are silly. Academic physics has been committing a Type II silliness error, where something is very silly but academia views it as not silly.

This is a strong statement, but it is what I will be attempting to establish. I hope that, from this perspective, it will be clear why I have delayed talking about complex craziness until simple sanity is established as a foundation for discussion thereof.

Yes, I talk about these ideas as if they are obvious. They are. It's important to remember that while learning quantum mechanics. It's not difficult unless you make it difficult. Just because certain academics are currently doing so, is no reason for me to do the same. I explicitly said at the outset (in "Quantum Explanations") that the views I presented would not be a uniform consensus among physicists, but I was going to leave out the controversies until later, so I could teach the version that I think is simple and sane. Bayesianism before frequentism.

I thought I was taking Tegmark's word on infinite universes and inflation, but I would seem to have misinterpreted that word, as verified by Wikipedia; my apologies to my readers. I've edited accordingly. It is not an important point except for people having emotional problems with many-worlds.

Greg Egan also said:

"Though a handful of self-described Transhumanists are thinking rationally about real prospects for the future, the overwhelming majority might as well belong to a religious cargo cult based on the notion that self-modifying AI will have magical powers."

Maybe it's time to stop holding up Greg Egan like some kind of icon.

"But what do all these posts have to do with your Artificial Intelligence work?"

Some of us are in fact pleased by how closely this does have to do with your AI work.

Maybe it's time to stop holding up Greg Egan like some kind of icon.

Why? Quarantine and Permutation City are still really good books. Egan is a icon of idea-based science fiction, not an icon of futurism.

Maybe you can admire someone who directly thinks you're a crackpot, but I can't.

"Yes, I talk about these ideas as if they are obvious. They are. It's important to remember that while learning quantum mechanics. It's not difficult unless you make it difficult. Just because certain academics are currently doing so, is no reason for me to do the same. I explicitly said at the outset (in "Quantum Explanations") that the views I presented would not be a uniform consensus among physicists, but I was going to leave out the controversies until later, so I could teach the version that I think is simple and sane. Bayesianism before frequentism."

That self-flattering interpretation of the first 4 sentences of this quote is pretty clearly not what Jess Reidel meant. He meant that you promote some of your ideas like there is no significant probability that they're wrong ("obvious" in that sense), when expert consensus differs from that assessment. As for the last two sentences, perhaps he'd be satisfied with a more prominent and obvious disclaimer. For example, at the moment of presentation of the simple and sane version of each explanation, clearly noting that reasonable controversies exist.

Elsewhere in his post he was pretty clear that your attempts to

Hopefully and Jess,

I understand what you're saying, but I truly and honestly believe that quantum physics as it works in the real universe truly is a hell of a lot simpler than the arguments that people have about quantum physics. I think the arguments are overcomplicated and pointless. Every time I even mention their existence, I worry whether I'm unnecessarily confusing the readers.

Let's start with the simple version. It's even the majority version - no, not the unanimous version, but the majority version among theoretical physicists, yes.

I'm not sure it's possible to teach quantum physics in blog posts if you try to teach the arguments too. The universe is simpler than our arguments about the universe.

If you want a dutifully gracious introduction to quantum physics that carefully acknowledges all the different positions and tries to explain their supporting arguments - treating all sides with respect, and dismissing no idea still believed by a substantial faction of physicists - then there are plenty of books out there which will be happy to confuse the hell out of you.

"... the overwhelming majority might as well belong to a religious cargo cult based on the notion that self-modifying AI will have magical powers."

"Maybe you can admire someone who directly thinks you're a crackpot, but I can't."

I have a high regard for most extropians (a subset of Transhumans, I think) I know well, but that doesn't make me believe that the Egan line is more than hyperbole at most. I don't take it as a slur against anyone whose name I know. I've certainly seen evidence that the majority wouldn't be able to distinguish the magical explanations that appear.

And the fact that Charles Stross thinks that discussing Extropianism is attractive to his market makes me think Egan has more truth on his side.

But I also want to mention Egan's "Diaspora". I bring it often as a great fictional depiction of an AI awakening. I know, I know. "Arguing from fictional evidence." But many people expect coming to awareness to be magic, and Egan shows how it could happen in a step-by-step manner.

Hopefully: If an exact duplicate of you 10^(10^29) light years away was being tortured you would know because torture is the description of a physical state. Another copy of your physical state can't be subject to torture without your also being subject to it. OTOH, I think that you are imagining a physical system that has evolved from a system that was, when described classically just like you. Such a system doesn't transmit any information to you so your consciousness can't be of it being tortured.

When I say "me" here, I mean my consciousness, the one I'm experiencing right here right now in this locality. So I think it's your OTOH statement that would be relevant. I read from your post the reasonable point that it's a presumably impossible paradox that any exact duplicate of me would be tortured while I am not, because then it wouldn't be my exact duplicate. But presumably by the same big universe logic, 10^(10^29) light years away (or closer) something that is otherwise an exact duplicate of me IS being tortured. Sucks to be that guy! :P

I just wanted to say I've benefited greatly from this series, and especially from the last few posts. I'd studied some graduate quantum mechanics, but bailed out before Feynman paths, decoherence, etc; and from what I'd experienced with it, I was beginning to think an intuitive explanation of (one interpretation of) quantum mechanics was nigh-impossible. Thanks for proving me wrong, Eliezer.

The argument (from elegance/Occam's Razor) for the many-worlds interpretation seems impressively strong, too. I'll be interested to read the exchanges when you let the one-world advocates have their say.

Hopefully: What do you mean by saying that your consciousness is "in this locality"? How is consciousness "in a locality" at all? "(Stop the presses! Shocking news! Scientists have announced that you are actually the duplicate of yourself 10^(1029) lightyears away! What you thought was "you" is really just a duplicate of you.)" was a joke.

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