Here's an interesting series of papers that examines the terms in the Drake equation using a lens similar to what you discuss here. The studies are an attempt to lay out how we could test and potentially falsify the hypothesis that we are typical observers in a multiverse


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It *is* the same stuff Sean Carroll is on about. Remember this is a world where Rupert Sheldrake and Roger Penrose find audiences.

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This sounds like the same bogus unobservable crackpot hype that Sean Carroll is pushing.

I've got a better idea for you to chew on after the LHC finds nothing and people start to get really desperate when the funding for crackpot research goes away:


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The pre-inflation past would be high-entropy in any case.

I'd assign a rather low probability to that. Physics is thought to be reversible - and the idea has stood up well over the centuries. For an early entropy decrease, you'd need irreversible physics - or enormous spans of time. I am not currently aware of any evidence favouring irreversible physics - and I don't think you can argue that the universe is likely to have started in an arbitrary state, and then stumbled upon a low-entropy zone by chance - since that hypothesis would not predict the incredibly-low entropy beginning we seem to see. Also, complex initial conditions would themselves need explaining in the face of Occam's razor.

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I tend to agree with you. Have you perchance read Greg Egan's "Permutation City"? The "dust theory" of that book - patterns finding themselves (which is what you are essentially saying) - is very intriguing, and the more I've been thinking about all the metaphysical problems involved in "traditional" theories, the more I find a "dust theory" attractive.


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Here's how I understand your argument.

1. There is a high probability that the Universe is very large.2. If the Universe is very large, then there is a high probability that we are in a low-entropy region.3. Any low-entropy region will lead to an asymmetry in time.

This is interesting, but it's sure a lot of extra machinery for this kind of claim. The claim you're interested in would be the past-hypothesis: the initial conditions of the Universe pick out a low-entropy state. Why not simply posit this as a fact about the Universe, instead of going through the exercise of (1) and (2)? Here's two reasons why it's worth considering:

First: there is no probability space in which (1) makes sense; andSecond: (2) seems to be false.

No matter what interpretation of probability you adopt, defining a probability measure on the "space of possible Universes" will be completely meaningless. This suggests there is no meaningful way to precisely state (1), if one has any empiricist scruples. And if the Universe is infinite, as our best models now suggest, then the probability that you'll end up in any finite region is 0. So (2) would simply be false. I suspect there are no bullets to be bitten here, before these problems are worked out more carefully.

Thanks for the interesting post!Bryan

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For your allusion to Copernicus, cite the source directly - he begins with beauty and with art in his introduction. It is so nicely written I take the liberty of quoting the opening in full:

"Among the many various literary and artistic pursuits which invigorate men's minds, the strongest affection and utmost zeal should, I think, promote the studies concerned with the most beautiful objects, most deserving to be known. This is the nature of the discipline which deals with the universe's divine revolutions, the asters' motions, sizes, distances, risings and settings, as well as the causes of the other phenomena in the sky, and which, in short, explains its whole appearance.

What indeed is more beautiful than heaven, which of course contains all things of beauty? This is proclaimed by its very names [in Latin], caelum and mundus, the latter denoting purity and ornament, the former a carving. On account of heaven's transcendent perfection most philosophers have called it a visible god. If then the value of the arts is judged by the subject matter which they treat, that art will be by far the foremost which is labeled astronomy by some, astrology by others, but by many of the ancients, the consummation of mathematics.

Unquestionably the summit of the liberal arts and most worthy of a free man, it is supported by almost all the branches of mathematics. Arithmetic, geometry, optics, surveying, mechanics and whatever others there are all contribute to it."

- N. Copernicus, De revolutionibus, Introduction, Book One

This preoccupation with the beauty and elegance in science is not a solely a Western phenomenon, it can also be found in Abhinavagupta and in Buddhist natural philosophy as well.

Note also that Copernicus is interesting in that he begins to separate science from what was then called "natural philosophy," when he later says:

"However, since different hypotheses are sometimes offered for one and the same motion (for example, eccentricity and an epicycle for the sun's motion), the astronomer will take as his first choice that hypothesis which is the easiest to grasp. The philosopher will perhaps rather seek the semblance of the truth."

What is the difference to Copernicus between the practitioner of this new science - astronomy - which he distinguishes from its Medieval name "astrology" - and the philosopher? Yet even as Copernicus struggles to create science, he insists on retaining beauty!

Thus I ask you mjgeddes, would you agree that Robin's foray above meets Copernicus' criteria of being both "beautiful" and "easy to grasp," despite being perhaps unexpected?

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Nice reasoning, but are you sure that time assymetry always holds in this universe? Teleporting even individual photons, even accross the Danube, seems to cast some doubt on that.

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Similarly others argue that a correct counting makes ordinary brains more common than Boltzman brains, though this also isn't entirely clear. Since 'ordinary' brains are a subset of Boltzmann brains, that would have to be a truly extraordinary redefinition of 'correct'.

whatever it is that's encoding me seems to be encoding rather more regularity and so on then is necessary to just encode, well, a few minutes of me. The order you perceive is a property of you, the information processed by your algorithm. Not the environment running the algorithm.

The walks through Libraryspace that do not preserve the illusion of continuity far, far outnumber those that do. But in worlds where that continuity is not preserved, either you do not exist at all or you do not perceive the discontinuity. The more properties of the algorithm that aren't preserved in 'switching' from one instance to another, the less likely it is that the two fit the criteria for a valid continuity.

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Caledonian: You're right in that what I'm fundamentally implemented on isn't so much a concern. The issue is that _WHATEVER THAT MAY BE_ seems to contain/encode more order than, at least at a surface glance, would seem to be justifiable with merely anthropic type arguments. ie, whatever it is that's encoding me seems to be encoding rather more regularity and so on then is necessary to just encode, well, a few minutes of me.

Maybe you're seeing some obvious thing here that I'm missing, but, well, if so, then there's something I'm missing. I remain confused on this issue.

Robin: That paper you mention, does it explain about proper counting solving the Boltzman Brain problem, or do you mean that's something that others have done entirely separately. If so, if you happen to know the basic idea, well, what is the basic idea about that? Thanks.

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Good interesting first attempt at an answer Robin, but it's more likely that the time asymmetry can only be explained by....universal terminal values...built into the structure of the universe.

Tim said:

'A better way of looking at is is that low-entropy initial conditions have an extremely short description - and are therefore preferred by Occam's razor.'

But of course this merely pushes the question back to accounting for Occam's razor again. Occam's razor only works because for every knowledge domain there are associated *aesthetic principles* (built-in design principles- not neccesserily human) which provide appropriate initial constraints.

Even at this early stage of theorizing, I am very confident if there are universal terminal values, the objective morality is likely very closely associated with the creation of beauty. Now that all readers know, get out there and make some good art! ;)

"...Copernicus' aesthetic objections to [equants] provided one essential motive for his rejection of the Ptolemaic system...."

- Thomas Kuhn, The Copernican Revolution

"All of us had been trained by Kelly Johnson and believed fanatically in his insistence that an airplane that looked beautiful would fly the same way."

- Ben Rich, Skunk Works

"Beauty is the first test: there is no permanent place in this world for ugly mathematics."

- G. H. Hardy, A Mathematician's Apology

Paul Graham: Taste For Makers

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Sean: [Regarding] patches of universe like ours today ... standard counting would suggest that only an infinitesimal fraction of them came from low-entropy inflationary beginnings. That is, given a patch with something like our current medium-entropy configuration, it is overwhelmingly likely to have come from a high-entropy past as well as evolving toward a high-entropy future.

The recent paper I cite above argues that counting correctly does say patches like ours are more likely to have come from inflation, though they and I admit it isn't entirely clear. Similarly others argue that a correct counting makes ordinary brains more common than Boltzman brains, though this also isn't entirely clear. But yes the pre-inflation past would be high-entropy in any case.

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I notce that I'm not seeing the walls dissolve, I notice that I'm not actually floating in the middle of space and dying of decompression, Although 'normal' human bodies are a subset of the possible Boltzmann Brains that encode the algorithm that constitutes your mind, they are an insignificantly tiny fraction of the total possibilities.

You're making several errors: you're assuming that the Brains that are running your consciousness are actual brains, and you're confusing what happens to the Brain with what your consciousness experiences.

Does it matter to an implementation of Conway's Game of Life whether it's being run on a Mac or an Apple or a PC or a Cray? If you compute T1 to T2 for a pattern, end the program, and fifty years later run the program to compute T2 to T10,000 for that pattern, do you think the pattern knows the difference?

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Caledonian, consider it this way:

I notce that I'm not seeing the walls dissolve, I notice that I'm not actually floating in the middle of space and dying of decompression, I notice that my brain has encoded in it a memory of me, say, making the bed this morning and by golly, that seems to coincide with what I observe now, specifically that my bed is made.

All of these things seem to be an excess of order, way more than is needed to instantiate me for a bit of time.

So I remain confused on the whole Boltzman Brains issue. Clearly there's something I'm not understanding here, something is missing in my model of the world, and (at least) in my model of Robin Hanson's model of the world as depicted here.

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Why is it that I seem to percieve more order, more structure than is needed for me to exist for, well, a brief interval?

Because 1) the perception of the order and structure requires more than a brief interval, 2) your wondering why you perceive so much order and structure takes even longer, and 3) any duration of existence, no matter how brief, is 'continued' in other sections of the Many Worlds.

If you have not already, you should read "The Library of Babel". How long is the longest text contained by the Library?

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Caledonian: Perhaps I ought be more precise.

Why is it that I seem to percieve more order, more structure than is needed for me to exist for, well, a brief interval?

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